MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - TF brakes - problems continue

So having had one rear wheel cylinder lock up, I stripped down and replaced both, then replaced the master cylinder with a rebuilt original. Carefully reassembled and bled the system, I set the pedal clearance to 1/2", and went for a test run. On my return all seemed well except the front drums were a bit too warm and the pedal clearance seemed to have reduced. In fact the pedal went from nothing to everything in about 1/2". So backed off the adjustment on the front drums as far as it would go. Next step, back under the car and shorten the brake push rod. In fact its now out of adjustment. Pedal feels slightly better, but still goes from nothing to everything in about 3/4". Jacked up the front and the back to check the brakes are releasing, which they are, but I'm not happy and have run out of ideas. What have I missed?
Dave H
Dave Hill

Try checking hand brake adjustment.
JIM N

There have been problems with rebuilt cylinders not returning to uncover the recuperation hole which will lock up the brakes as the fluid warms.
When I have done them they all seem OK until they have been in use a bit. I have never had this with the seal kits from the Octagon car club.
IF you take out the M/C filler cap and push the pedal you should see a spurt of fluid go back into the chamber, if not then the piston is not fully returning. The distance involved is in the thousands of in inch range.
Also this hole may need clearing with a bit of fuse wire.If you look at fig M14 in the WSM you will see 2 drillways the rear one is quite large but the front is smaller and does not go all the way to the bore but is continued with a very fine drillway.See page M4 explanation
This may be a long winded reply but it has paid off with mine and a few friends cars.
Ray TF 2884
Ray Lee

sorry M14 drawing is incorrect as it shows the recuperation hole behind the seal edge Fig M2 is right. As I said, the spurt of fluid is the giveaway.
By the way use a mirror, your eyes are too valuable.
Ray Lee

Ray. Yes you are right, one of the holes is tiny and easily blocked. Have been reluctant to do that because I have a remote brake fluid reservoir attached to the lid. Will have to go for it.
Hand brake adjustment OK, as the rears are fine.
Another test run and I've noticed that the front brakes are not releasing fully, whilst the rears are doing so. I loosened a bleed nipple on the front and that side let go immediately. Now suspecting the brake hoses might be blocked.
Dave H
Dave Hill

What are the chances of TWO hoses blocking at the same time?.
Fully slack off one micram adjuster at the front and push the brake pedal. If the shoe does not return when you lift off then release fluid at the chassis end of the hose, if it then returns then the hose is OK then check the other side. If they are both OK then the problem is M/C.
I have had all of these problems in 40+ years of ownership. Once had to drive home with a mole grip on the rear hose when a seal failed completely!
Ray TF 2884
Ray Lee

I have to agree with you. Similar experience myself, but mostly witth other vehicles, and only 4 years with the TF. Have never had so many braking issues before. I'll try what you say.
Dave H
Dave Hill

Ray. You were right, of course, its the master cylinder.
I'll be doing the fuse wire trick tomorrow. Thanks.
Dave H
Dave Hill

How are the return springs in each drum? If it takes a lot of effort to get the shoes on and connected then they are probably OK. From memory I think there is a choice of spring holes?

Matthew.
M Magilton

Its a good thought, but I confirm that its a fight to get them back on. There is a choice of spring holes, but they are set the same as in the WSM. When I changed the master cylinder, all appeared to be well, but things deteriorated, so a blockage from contamination could be the cause. I will be removing all the fluid in the master cylinder and remote reservoir.
Dave H
Dave Hill

the hole in the cylinder is in the 0.025" range, use the finest wire you can. You don't want it sticking in the hole. Been there!
Ray
Ray Lee

What a nightmare job. Carpets and steering wheel out and I was sprawled over the car with my head in the footwell struggling to see to get the wire in the hole. Desperately uncomfortable for an oldie. Might have been a shade more difficult because of the stainless steel liner - the hole in the casting is easy to find but at the base of it is the liner with a tiny hole. Anyway find it I did. Now putting it back together.
Dave H
Dave Hill

If the wire went through at least you know the piston is fully retracted.
I have a removable door stays and pins in the hinges, it is much easier with the door out of the way.
Ray
Ray Lee

It has to be much easier with the doors off. Yes it went through ok (0.022" wire). Refilled with new brake fluid and have just had a short test run. Probably better, but not entirely happy. There is a bit more pedal movement, but there should be as the micram adjusters are fully retracted. Still a bit of friction turning the front left wheel. Brake lights switching off when pedal retracted. Front drums quite hot and rears barely warm after 3miles at up to 50mph and moderate braking. Will try again later.
Dave H
Dave Hill

Don't forget your fronts are twin leading shoe (self servo effect) where as the rears are 1 leading 1 trailing. The fronts with 2 cylinders do much more work. Just did a run and my fronts hot and rears warm just like yours.
Ray
Ray Lee

Decided to strip the front left drum. I found a great deal of brake dust in there. Cleaned it up and checked pistons clear, which they were. Replaced the brake hose - nothing wrong with the old one I found but I think that pumping some fluid through to clear any air helped a bit maybe iin passing more fluid through the master cylinder. Another test run coming on.
Dave H
Dave Hill

Dave, am I correct in remembering something about Dot 5 fluid having an effect of swelling the seals in the master cylinder and blocking the return hole, thus causing brakes to stay on? And was there a difference in seal material for Dot 4 and Dot 5?

Not sure whether this is the same as you are experiencing ...

David
David Wardell

Its a myth I think. Conventional glycol ester brake fluid is more aggressive to most rubber types than silicone.
Dave H
Dave Hill

Have gone through the whole procedure of clearing the recuperation hole in the master cylinder again. Couldn't get a wire through the hole so I used a magnifying glass and long modelling pin held in a pair of long nosed pliers. That did it, whatever was in there was solid. Followed up with the wire. Put it back together then went for a test run. I've come back, parked up and the brake pedal is solid again! The cause has to be contaminated brake fluid. Will purge as much as I can and go through the whole thing again!
Dave H
Dave Hill

Old school methodology was to purge the system using mentholated spirits. I know a RAAF fella who thought he was making strides using aviation hydraulic fluid in his Toyota brake system, only way to recover from the boo boo was to purge using metho, blow dry and replace every rubber component.
G Evans

I know it is a PIA but the only way to go is remove the M/C. and clear it on the bench. If the pedal is solid ie, all clearance has disappeared then it can only be a recuperation hole problem. If it was a piston return problem then the clearance would get greater.
It is a long shot but check there is no interference between the clevis pins on the bottom of the clutch and brake levers. I have seen incorrect ones fitted.
Ray
Ray Lee

I removed the brake master cylinder yesterday, dismantled it, flushed with meths and reassembled it. There was some black deposit in there, but..... the problem is still there! Pumping the pedal results in less and less movement and the brakes drag. The push rod is adjusted to as short as it will go, and I've already ground an 1/8" off the end. Final thought this morning was that the thread on the fork end might not be bottoming out in the push rod end fully (bottom of threaded hole clogged). I'll also check the clevis pin, though I believe to be clear. Thanks.
Dave H
Dave Hill

Still pointing to the master seal not uncovering the recuperation hole every time.
I have had this a few times with rebuilt cylinders.
Bench test it a few times while warming with a heat gun, I run a pipe from the outlet to the filler and move the piston only 3/16". Remember the exhaust pipe goes right past it on our cars.
Ray
Ray Lee

Yes indeed. If necessary I'll grind a few thou off the face of the piston, but first I'll check the pushrod. I'm getting to be an expert at removing the master cylinder. Refitting is a bit more difficult, but even that is much easier now I've done it a few times!
Dave H
Dave Hill

I would not mess with the piston your life could depend on it. When fully back it should butt up to the retaining washer. If you can't get it perfect then you should buy a new one, the Octagon car club has the TRW cylinder on stock £70 members £77 non members. This is the one that now seems to be recommended and not the AP one.
A single line brake system does not give you a second chance.
Ray
Ray Lee

Dave,
I would second Ray's comments on the safety issue-not worth the hassle for £70.

Regards
Declan
Declan Burns

I had a TRW master cylinder in there when this problem started, gave up on it, had my original refurbished and here we are. I have the refurbished one out of the car again and in a bench vice, with a pipe from the outlet to the filler, as you suggested. Recuperation hole clear and it pumps fluid. Nice, simple way of testing. Warmed up with a heat gun and no change. Ill give it another go to check.
Dave H
Dave Hill

sorry to harp on about this. The piston MUST come fully back until it contacts the piston stop.( part 17 fig M2 in WSM. )
If the brakes lock on it can only be the recuperation hole either blocked or not being uncovered by the seal lip, we are talking 25 thousands of an inch here very critical. when testing only move the piston slightly, if you go further the velocity will overcome any tightness. When in the car the piston only a little bit. Been through this nightmare myself only to find an intermittent sticking piston.
Ray
Ray Lee

Harp on as long as you wish Ray, its all good stuff for which I am grateful. Yes, moved the piston successively only 3/16" and got a small spurt of fluid each time. Recuperation hole definitely not blocked now. Others have reported a similar problem, some years ago, and attributed it to a tight cup seal, with an alternative mentioned. Somebody has just kindly posted that discussion again. Can't find the seal mentioned though. If its not the recuperation hole blocked, it can only be the seal not uncovering the hole, as you say. One thing that concerns me with a stainless steel liner is that there could be slight differences in friction properties and dimensions. Thousands have been happy with this mod though.
Dave H
Dave Hill

There was a post (which I can't find) which mentions S/S having different friction values. My present M/C was re-sleeved by Pastparts Ltd and was fine. Maybe your cylinder needs a light hone.
Ray Lee

Yes I used Pastparts as well. Might dash down to B&G tomorrow (only 20miles) and get a replacement seal kit in the hope that it makes a difference.
Dave H
Dave Hill

I rebuilt the entire brake system on the TF using new wheel cylinders, a TRW master cylinder, new hoses and cuniffer pipes. After leaving the car for a couple of weeks without use, the brakes locked on solid. After days messing around I found the problem was my fault. Before I had fitted the new wheel cylinders I had put a smear of waxoil under the rubber dust boots. This had solidified and when I pressed the pedal there was sufficient force to push the piston out but the springs couldn't return them due to solidified waxoil. After a good clean and lubricating with proper rubber grease the brakes are fine. Are you certain the wheel cylinder pistons are free? I have seen new ones that had been on the shelf for some time and they were very stiff. I do sympathise, there is nothing worse than having your clothes and hair saturated with brake fluid and it also isn't too kind to your hands.

Good luck

Jan T
J Targosz

Yes they are all free Jan as I have checked them.
In my case they are lubed with silicone brake fluid and silicone grease. I've checked and double checked everything, and replaced lots of things, but still have a problem.
Dave H
Dave Hill

The symptoms you describe sometimes are caused by a hose swelling shut internally, a clamp pinching a hose, or possibly a crushed/kinked steel line. High pressure from the master cylinder can apply brakes but the springs on the shoes/disc caliper can't provide enough effort to release the brakes. Hard to imagine new hoses going bad and there are no hose clamps, right? Is it possible the steel line from the 4 way fitting to the front got crushed or kinked on installation?

You might crack the bleeders one at a time just like bleeding the brakes, but this time feel how much effort the pedal takes, fronts vs rears.
JIM N

I bought three new hoses just in case, but having replaced one at the front, finding absolutely nothing wrong with it, I have done no more with the others. The brake lines are Copper or CuproNickel and relatively soft, so fairly easy to crush, but not seen anything.
Crack one bleeder and they all release - this indicates to me that its a mastercylinder problem. Having said that, I don't have a 4 post or any other lift, just a trolley jack and a set of axle stands, so I don't go round and jack up every corner each time I do something, just the pair of wheels that are in the air at the time.
Dave H
Dave Hill

Well I did go to B&G and buy a mastercylinder seal kit. Looked very promising with the important seal much like the recommended one in the other thread on master cylinders. Took the master cylinder out again and dismantled it to find that the seal already in there was much the same and looked fit for purpose. I changed nothing and put it back. Will just have to see if I can live with it as is. No long jiurneys planned.
Dave H
Dave Hill

OH Dave - I feel for you mate.
Bloody MC is not the easiest thing to get to anyway - let alone without a lift.
I can't understand why the piston does not retract beyond the relief hole... To release the pressure in the system. From the other thread - it is fairly clear the seal on the piston is sometimes supplies with the incorrect specs. There is a radical difference between the fit of both of them. Buds pictures show that. (Attached)
I know when I was sold the wrong fluid as soon as I got to the States. I had to replace all the cylinder seals and the master cylinder - A kit for the original MC I could not find? So had to buy the lookalike MC replacement from Moss. Also had to replace all the brake hoses as they too had swollen up and I could not bleed the rears at all. For just getting the wrong fluid (German hyro-lastic suspension fluid) It was a huge PITA.
I think you are on the right track with the MC seals Did you get the one Bud suggested? S7464 - It looks like the right one to me. Other than checking the little dished washer is the right way round :)
Hope you can sort this out Dave. Keep us informed.
There but for the grace of .......
Rod




Rod Jones

Dave, I'm a long way from home so can't reference any sources that this idea might have come from, and I don't recall it cropping up in this thread, but I seem to recall a reference somewhere to a sort of wavy washer that has to be in place somewhere in the assembly. There wasn't one on my mc when I took it apart (rather forcibly as it was seized solid). I mentioned it to the guy I took it to to be resleeved and he nodded wisely but made no comment. Mine is years away from a trial run so I can't tell if I will have the same problem. Clutching at straws on your behalf!
Chris
C I Twidle

Yes, what's in there now looks exactly like S7464, but its a different number, ditto the seal that I got from B&G. Which is why I left it in there.
I can jack up the car, get the master cylinder out, strip it, rebuild it and put in back in about an hour now. Not bad eh (for a pensioner)! But its not a pleasant job.
There is a brass dished washer that has to be fitted the right way round, and it is.
Chris, I'm sure yours will be fine.
The car is a runner and I will be going to Kimbolton Fayre on Sunday come what may. I just won't be leaning on the brakes more often than I need to. It'll be fine.
Dave H

Dave Hill

It is always the secondary seal that sticks the piston.The main seal collapses back to allow new fluid, that is what the wavey washer is for.
I am surprised that,if the system is pressurising it is not pushing the piston back to the recuperation hole.
The system has a static pressure of about 8 psi to keep the seals seated. It has been known for the foot valve rubber to be left in place and another on fitted on top. This would increase the static pressure. (just a thought)
Ray
Ray Lee

Yes, its a mystery. The pedal movement just gets less and less, and there is more friction resisting turning the wheels. All I can think of is the piston is a rather tight fit in the master cylinder bore and the piston doesn't fully return. With use it should improve.
Dave H
Dave Hill

Suggestions: Don't even think of driving it until it is sorted. Get rid of your remote reservoir for now- that just adds complexity and one more possible problem. With the cylinder out, the piston should move freely in and pop out with minimal to no drag. If it is binding, something is wrong. Measure the cylinder bore- I think it is supposed to be exactly 7/8". Make sure there is not an extra washer stuck at the very end of the bore. As Bud and I found a few years ago, the rebuild kit secondary seal internal rim did not seat into the groove on the piston, thereby bulging the OD of the seal (as shown in photos above). There have been so many types of aftermarket cylinders/pistons over the years a mismatched piston/kit could be possible? Lastly, any chance the brake fluid you are using is contaminated? George
George Butz

All good suggestions, but I've covered all of them I think.
I've a new train of thought completely, that few in the USA will have experienced. I converted this car from LHD to RHD, which meant welding in a new pedal box and m/cylinder mounting plate. Its a mirror image of the LHD set-up. Position of the box is easy to get right, also the m/cylinder mounting plate, as there is only one place it can go. For the positioning of the pedal spindle tube in the chassis I used a long rod passed through the LH tube to find the equivalent position on the RHS, then drilled a hole and welded in the tube. But what if I was a couple of mm or so out? What would be the consequences for the brake push rod adjustment? As it is, it is as short as it will go, and I have shortened the end of it by 1/8" / 3mm in addition. Maybe its still too long! The symptons fit. The only doubt I have is, if this is true, why wasn't this an issue with the TRW m/cylinder that was in there previously?
Dave H
Dave Hill

Well folks, I reckon that's done it! Removed the m/cylinder again and ground another 1/8" off the push rod. I now have 1/4 - 3/8" proper play in the brake pedal, not quite enough but it will do for today. When
I am inclined I will remove another 1/16" and it should be perfect. Enjoy the rest of the weekend.
Dave H
Dave Hill

Perseverance rewarded!
Enjoy Kimbolton, we are enjoying the Cotswolds.
Chris
C I Twidle

The pedal box to pivot pin position is indeed critical. The pedal pad - pivot pin - M/C pin ratio is about 5 to 1, so 1/16" out is 1/4" clearance lost. Have seen this on another conversion but forgot to bring it up.
I have also found that replacement cylinders have varying depths in the piston seating for the push rod.
At the moment I hate brakes, I have lost the internal adjuster from my MX5 brakes, so it is up on stands for a few days. I know that when the new one arrives I will find the lost one.
Happy MotorinG
Ray
Ray Lee

Ray, as you seem to be on intimate terms with the MX5 mc as well as the T series what would you think are the chances of using one to create a dual circuit brake system for the TF? Is there enough space between the box and the cross member?
Regards,
Chris
C I Twidle

The MX5 M/C is not suitable for use in the T Type. There is a post in the archive of somebody fitting a dual cylinder. Search "Dual circuit master cylinder"
Ray
Ray Lee

Quiz local kit car clubs they seem to have a lot of knowledge on adaptions. Also racing groups as they have a lot of one offs.
Ray
Ray Lee

Thought I would revive this from the archives as I have been in and out of the problem for the last 12months and I've seen others with similar issues. The master cylinder has been back out numerous times, new push rod fitted, and much brake fluid expended. No adjustment left on the threaded adjuster to get the required free play, and its as short as it will go. So what to do?
Firstly, shortening the push rod itself is a bad idea because if you do so, it may not penetrate far enough into the hole in the mastercylinder piston, reducing its stroke. Secondly, slightly reducing the length of the threaded end of the yoke so that it fully penetrates the pushrod is better, but its a marginal improvement. Nothing left to do then? I now realise there is another option and its probably the cause of the problems all along. Its to do with the mechanics of the pedal itself. The rearward movement of the brake pedal (pressure off) is limited by the pedal stop bar welded across the middle of the pedal box. If it is slightly misplaced or the pedal casting slightly misshapen from original (both options possible on a RHD conversion), the pedal won't return /come to rest where it should. In such a case the required length of the push rod and yoke will appear shorter than original specification. The solution I imagine is to remove a small amount of metal from the front of the stop bar or the back of pedal casting. Finally solved it, I think.
Dave H
Dave Hill

Had the same problem with my TD when I rebuilt the MC. Found the new piston was longer then the old one. Cut the face off on the end that buts up to the clip that keeps every thing in MC bore to let seal uncover the little hole more. No more problem . The rod adjustment doesn't hold the listen back the clip does. Forrest TD/C/22679
Forrest Rubenstein

Forrest. I didn't quite understander your explanation, there is a typo in there - can you elucidate please. Just in case I need another fix!
Dave H
Dave Hill

Dave I didnít read down through all the comments so excuse me if this was discussed previously.

I had a similar issue with TD-4834. I had an original Lockheed MC that I kitted, replaced all the conifer tubing, new hoses and wheel cylinders and used DOT 5 when I did the restoration. I kept having the same issue. I fought with the brakes for over a year and could never figure out the issue. Even had to call upon ďthe ride of shameĒ several times as they would lock up solid and I would be unable to move the car. By the time the car was delivered to the house the brakes had released. Iíd take the MC apart, put it back together and reinstall with the same result. Very frustrating to be sure.

After a long discussion with Mike Shea, he is the PO I got dadís car from, he relayed the following to me... During TD production Lockheed made a change to the piston. Early MCs didnít have holes drilled into the head of the piston. The replacement kits are not compatible with the early pistons with no holes as the waffle plate behind the cup seal canít relieve back pressure. I ended up using a NOS Lockheed kit Mike supplied me with the correct piston with the relief holes. Problem solved.

Hope this helps

Bill Chasser
TD-4834
W A Chasser

Interesting information - I think its the same issue mentioned by Forrest above. If I understand him correctly he machined some material off the back end of the piston to achieve the same thing. In response I would say that I had the mastercylinder rebuilt and a stainless steel liner fitted by specialists, who tested it before sending it back to me, so it should be correct. I also primed and tested it on the bench before installing. I am going to investigate the pedal movement, but if that fails I will look again at the piston and seal. Thanks
Dave H
Dave Hill

This morning I removed the steering wheel and carpets to gain access to the pedals. Next step was to remove the pedal tops (easy), metal frame and gaiter. Removing the metal frame was extremely difficult, as on a RHD car with HiGear 5 speed conversion the moulded gearbox cover obscures one of the screws. Not wanting to remove the gearbox cover I cut away 1/4" of material over the screw and managed to extract it. The rubber gaiter came off fairly easily and split free. All this done, access to the pedals is very limited, however with a mirror and finger tips I could establish that the brake pedal was hard against the rear stop / pedal box crossbar. Releasing one of the bleed screws enabled me to push the pedal far enough forward to gain access to the small gap created at the back of the pedal. With the aid of a tapered burr I ground a small recess in the pedal stop / crossbar. This seems to have given me a little more pedal clearance. Now I need to put it all back together and see if it has improved matters.
Dave H
Dave Hill

Much better, though brake light remains on occasionally. Pedal return stll a bit slow occasionally - push rod adjuster rubbing on the master cylinder gaiter I think. Improving with use.
Dave H
Dave Hill

But not good enough. Removed and dismantled the master cylinder for the nth time. Swopped all the seals except the main seal. Bill was right, they do vary in thickness, but the one in there was the thinnest I had, so it went back. All cleaned up and reassembled, compensation hole completely clear as it should be. Pump it dry, except for a little bit of lubrication and operation as smooth as silk. Excellent, fill with brake fluid and tube back to the reservoir, then pump again to check flow. No longer smooth. Judder, especially on the return and its stopping 1/8" short of the back of the cylinder, plus a leak.. Compensation hole completely clear. What on earth is going on? Empty the brake fluid, check seals and try again. Same thing. Empty again, then thoroughly clean and inspect the bore, which I can see is scored at the back end - not severely, but enough. How? Its got a stainless steel liner (scored). Rear edge of the piston has some sharp / rough edges, so stone those off. But can't halp thinking push rod alignment had something to do with it as well.
Dave H
Dave Hill

I finally worked out the cause of my brake problems - the master cylinder is mounted too close to the pedal assembly (maybe only by a few mm). The pedal box and backplate were proprietary parts and should have been correct, but I welded them in. The proximity explains why there is no adjustment left on the pushrod. The damage to the master cylinder bore is caused by the push rod pressing the piston hard against the bore. As the brake pedal pivots, the push rod angle varies as it enters the master cylinder piston where there is just enough clearance for it. When the master cylinder is mounted slightly closer, the clearance is insufficient. To recover this by moving the master cylinder mounting plate is too difficult a job. Instead I have radiused the entry to the hole at the back of the piston, which has made a visible improvement to the tolerated angle and makes no difference to functionality or safety of the brakes. My final submission on this subject!
Dave H
Dave Hill

Dave, Iím in Narbonne, heading for Carcassonne tomorrow. itís my birthday and I think your ďfinal submissionĒ is almost as good as an extra birthday present!
Perseverance rewarded.
Chris
C I Twidle

Chris. It didn't work! I have a holiday home near Carcassonne and usually I would be there right now, but am working on the TF in the UK instead.
Dave H
Dave Hill

Well done Dave, so this was a LHD converted to RHD?

Peter
P G Gilvarry

Yes. The pedal box and mounting plate came from Metal Mickey in the UK. I polished the bore of the master cylinder and the action was smooth - put it in the car and the pedal is not returning. When I first rebuilt it, all worked well, then one day after driving down a steep hill, the offside rear froze. Checked everything, master cylinder in and out so many times that I am thoroughly pi**ed. Where to next?? I surrender.
Dave H
Dave Hill

Sorry about that, celebrations a little too soon. At least you have been in a better climate, our week on the Canal du Midi has been cold, wet and very very windy. Not at all what we expected from the South of France!
Iím afraid my only suggestion would be to consult with whoever did the resleeving to see if they can suggest anything.
Chris
C I Twidle

We were there in April and the weather was glorious, however our experience in general for that part of France is - cold Spring and early Summer, hot Summer and Autumn. Usually windy. The influence of the Pyrenees I think.
The bore of the mastercylinder is damaged, as is the bore of the "spare". Tried polishing and fitting both, but same result. If I could really see what was going on I could make new parts, but on my back under the car its purgatory.
Dave H
Dave Hill

Dave, see 'Brake/Clutch Interference in Pedal Box' in the archives. The cellphone/borescope that I bought for $30 saved me from that same under-the-car misery. Bud
Bud Krueger

Bud. You know, I had exactly the same thought last night - I have one of those and I've used it occasionally to look inside the cylinders. I am going to mount the master cylinder back on the car, but without the gaiter, so that I can see with the aid of the fibre optic camera, exactly what is going on. Won't be easy, but should be possible. On a RHD car both the clutch pedal and the exhaust pipe make access difficult. My expectation is that the pedal rod is entering the back of the piston at an unacceptable angle, but I need a good look at it to see how to correct it.. If so I may have to remake the U / stirrup that attaches to the pedal with an offset. There is always a solution.
Dave H
Dave Hill

Dave,
when converting LHD to RHD it is not only the accurate positioning of the pedal box but also the fitting of the pivot tube when welded into the chassis.
I know of one car that has an offset pivot pin and the top of the pedal box cut away to enable the pedals to be fitted.
If the hole for the clevis pin is not in line with the M/C possibly it could be welded up and redrilled to align. I don't think the change in leverage would make much difference.
Sorry to doom and gloom.
Ray TF 2884
Ray Lee

Ray. The pivot tube may be offset, but I was very careful with the positioning of it. At the moment its all conjecture, but if I need to make new parts from scratch or cut and weld the old ones, I can manage that. Taking a rest today.
Dave H
Dave Hill

Just thinking out loud here, but would a stronger pedal return spring help this problem?
best,
Jake
J Stone

I put a second spring on, but it made no difference. I was surprised too.
Dave H
Dave Hill

Dave
Like you I have an ex USA lhd TF converted to rhd. I too had problems with the master cylinder mounting plate, in my case it was because the weld nuts to secure the m/c had been located and welded in the wrong position particularly the rear one which was about I/4 inch too high. This meant that the m/c was at the wrong angle in relation to the brake pedal. Malcolm Green's, T Series Restoration Guide has a photo of the mounting plate on p.41 which shows that the holes for the weld nuts are angled to the centre line of the plate.
Fortunately I had this manufacturing error drawn to my attention before it was welded in place and it was easily corrected, possibly my plate came from the same source as yours?
Finally, not quite sure if you are using Dot 5 silicone fluid? I know some owners use this very successfully but in my experience it can cause problems with brakes sticking on on due to swollen rubbers, not all the seals currently available are compatible with silicone fluid. For comparison purposes I am using an AP m/c installed about 3 years ago and standard Dot 4 fluid from Halfords.
Roy
R.E. Miller

Thanks, very interesting. The parts came from Sportscar Metalworks, but I think he makes them for others as well. It seems to me that this is the kind of issue that I have. I will be looking more closely at it tomorrow.
Yes I do use Dot5 but am completely unconvinced this is a Dot5 issue. I have done my own tests as well as reading the very comprehensive testing done at a range of temperatures by the US Dept of Defense. In reality silicone fluid causes so little swelling on even very basic rubber formulations that they have to add a trace of a swelling agent to it to match the slight swelling effect of Dot4 brake fluid. In addition it seems that the rubber seals in most brake sytems are made of SBR (Styrene Butadiene Rubber) or EPDM ( Ethylene Propylene Diene Monomer) which in other vehicle applications would be considered unsuitable (nil oil resistance), but are good enough for brake fluid. This is because it is highly polar, and such rubber materials are extremely resistant to polar fluids. Besides all that I now have two slightly used master cylinders that have visible damage on the bore.
Dave H
Dave Hill

Double check the shoe orientations- if one is installed backwards, it can lock up. I know there's a semicircular notch on one end to rotate and flat at the other end to engage wheel cylinder, bit it is not impossible install one backwards.

I recently installed some new shoes on a Honda where it was obvious they paid no attention to where the brake material was bonded to the steel which meant they would not apply equally and potentially one might lock up.
JIM N

I jacked up the front of the car as high as I could get it to give myself more room for manoeuvre and assist visibility. With the rubber gaiter removed I could see that with the pedal at rest, the push rod was hard up against the inside of the mastercylinder piston at 11 o'clock, instead of dead centre and toward 12 o'clock. Pedal down and it looked more central, but hard to say as the adjuster obscures the view. The mastercylinder also looked slightly off line. This meant that the front mounting hole was slightly too low, and the mounting plate not perfectly parallel with the chassis. Too big a job to remove the mounting plate and weld it back correctly (body off probably). Instead I decided to pack the back of the mastercylinder with a large washer of suitable thickness and elongate downwards the master cylinder front mounting hole. I first drilled it with a 10mm drill bit with a 1/16" offset, then ran a burr through it, making an additional clearance of about 3/32". There is plenty of metal around the mountings, so no safety issue.
All back in now and much easier to get the mounting bolts in than before. Filled with brake fluid and the pedal returns fully every time, albeit with very slight drag. Brake light also goes out. Free play about 1/8".
So not perfect but I think its usable. Needs a carefull test run. First step a short run down the drive and jump on the brakes to check it stops and releases safely and repeatedly.
In summary, the problem seems to have been caused mainly by the nuts on the mounting plate not welded in the correct place (as related by Roy Miller above).
Dave H
Dave Hill

Next step will be to modify the fork that attaches to the pedal lever, so that the threaded end is offset. I will cut off the threaded end and refix in a better position to centralise the push rod in the master cylinder piston. Rather than weld it I am inclined to drill and tap then pin to the base of the fork.
Dave H
Dave Hill

OT, but this is for Chris Twiddle: did you see this poster in Carcassonne? It's upstairs in a cafe.

Dave, I'm glad you've nailed the problem at last. Frustrating. A not-too-tall friend of mine did this conversion on a TF from the USA
and realised just a little too late that he could have located the pedal box a bit further back to suit his leg length....

Regards, David


D A Provan

Thanks David,
We did check out a few cafes in Carcassonne but there were at least 7 in Place Carnot which our BnB overlooked.
Loved the citadel but, the less said about our week on the canal du Midi trying to steer a slab sided boat with a steering system with about as much control as a dyslexic brick (ie without bow thrusters) and in the teeth of a constant gale, the better!
Chris
C I Twidle

Any time you are there again, let me know. Our place is between Carcassonne and Limoux. My TF is in the UK, but I have a good friend / neighbour close by who has lots of interesting classic cars. For lively cafes in La Cite, go to Place Marcou.
The TF is now back in business.
Dave H
Dave Hill

This thread was discussed between 03/07/2017 and 25/05/2018

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.