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MG MGB Technical - Looks like slipping clutch, but isnt - any ideas?

On Wednesday my wife Dagmar found appropiate "Ersatz" wile her MGBGTV8 will get some tlc: a black rubber bumper GT, tinted glass, V8-wheels, steel sunroof.
The only disadvantage: the clutch slipps.
Today we pulled the engine, fitted a new clutch kit (and new crankshaft seals rear and front, and a new flywheel, and a new gearbox front seal). Old clutch plate had only 5 mm thickness, clutch pressure plate unit had excessive wear, bearing assembly was gone.
Test drive: same effect as before - "clutch slipping"-similar.
The hydraulic slave cylinder was in good order, the connection pin with the clutch lever the right one (not too long).
Nevertheless, I made a test ride, and after 30 miles the symptoms were nearly gone - only from time to time "clutch slipping".
Any ideas what this could be? Overdrive problems? What precautions are necessary?
Any comments will be highly appreciated!

Thank you very much in advance,

Andreas

PS: Here is the "new one" - sold on Feb 13 1976 by Henleys in London, fitted options are steel sunroof, tinted glass, black color (+50 Pounds!!) and headrests:
http://www.mgcars.de/
Andreas

A clogged clutch hose, or a defective master
cylinder (that doesn't release pressure) could cause
this problem. The clogged hose acts as a one-way
valve -- I think someone else ran into the same
problem in the archives.
Ronald

Sorry, pressed "submit" to early..here is the link to the black one:
http://www.mgcars.de/var/IMG_4441.jpg
Andreas

Ronald,

thank you, will check it!

Andreas
Andreas

Is it possible that there was any kind of residue(grease, oil, etc.) on the flywheel or pressure plate that would allow it to slip and has finally been burned off? As I recall my new pressure plate had some kind of protective coating on it, I don't know what it's called but I've noticed it a lot on packaged bare metal parts. Of course I made sure that everything was cleaned off properly before I assembled my clutch..
Jared Snider

Before I ever install brakes or a cluth, I always spray them with brake cleaner as they spray a protective coating on them its posible that that is whats making you clutch slip, it may burn off...
Ross

Andreas. I would look at the rubber hose between the hard line from the master cylinder and the slave cylinder. I always replace them any time I have the engine out. You also mention the overdrive. That also has a clutch which may be slipping. If the car seems to work properly in direct gears and slips in overdrive, the overdrive clutch may be the problem. Are you having similar problems with the clutch in the non-overdrive gears or only when the overdrive is switched on? I know that you are a very serious MG person with a large collection of MGs, hence, I understand that you would know to remove the "preservative" on the pressure plate. So, the final problem resolves itself to the flex line or the OC clutch. Les
Les Bengtson

Dear MG friends,

thanks for your answers and your kind words until now.
1. Hydraulic line: Watching the clutch lever during an engagement/disengament cycle of the clutch, it moves back to the default position.
2. Pressure plate: I treated all surfaces with brake cleaner and made sure, that there will be no grease on the cluthc plate.
3. Overdrive: I am not sure, but I think that the problems are bigger with o/d disengaged. By the way: the gearbox was filled with gearbox oil, I have changed it with engine oil during our works yesterday.
So far, will make another testride right know and keep you informed.

Regards,

Andreas
Andreas

Update:
120 test-miles today. Serious problems in 1st, 2nd, 3rd (without o/d) and 4th (without o/d) when engine (and gearbox) cold. No problems with 3rd and 4th with o/d engaged and engine cold. When engine hot, sometimes a problem occured, but never when o/d engaged.
Have changed oil again, another 30 miles testdrive. Seems to be a little better when engine cold.
Tomorrow I have a 300 miles business trip - I am too much MG enthusiastic, so I will take the risk and drive with the "new" black MG...will keep you informed.

Regards,

Andreas
Andreas

Based on my clutch problems (dragging, not slipping)
I don't think that the pushrod position is
sufficient to determine complete engagement/disengagement.

Even if the pushrod returns "almost" to
the clutch engaged position (say less than 1/16"),
I think there could be enough residual pressure
to cause ocassional slippage. I would immediately
replace the clutch hose with the MOCAL or
Goodridge stainless version just to rule
the hose out. The rubber ones
seem to leak after a year anyway.

Is there enough free play in the clutch pedal?
Not sure how this could happen, but what if the
pedal bushing is binding?

The worst case is a defective clutch cover
(weak springs, wrong dimension.) Or maybe even
the wrong clutch cover/disk (i.e. for a different
car.)
Ronald

All of the above are excellent points to check. There is a MGB in my small town(not mine) that has a clutch slave cylinder with a sticky piston. It would stick sometimes, preventing the clutch from engaging.With delayed action,it would release,and abruptly grab. It has finally stuck with the piston at the end of it's travel, holding the clutch disengaged, and all fluid leaked out. I tried pressing by hand to get it to release, and it is stuck solid.I am supposed to fix it as soon as owner buys the new clutch slave and flex hose. Point if story: I would rebuild the slave cylinder and remove all doubt of this component.

Regards;

Pete Haburt
Pete Haburt

Morgen Andreas,

I does sound like your overdrive is playing up.

Clutches tend to slip in the higher gears: You should have the symptoms worst in overdrive top and least in first gear. All dying clutches I have experienced have been like this and a logical consideration of the clutch and gearbox support this. (The engine produces a certain ammount of tourque at any one time and this torque will become too much for the clutch when it is weak. The car needs less torque to accelerate in lower gears than higher gears.)

I cannot comment from experience with the overdrive, but I do know they are sensitive to the oil used. Engine oil was specified and the use of additives was forbidden. Gearbox oil could well have contaminated the linings in your overdrive clutch. Perhaps regular use and a lot of oil changes could sort it out.

Mike
Mike

You can check the hydraulics are releasing completely by seeing how difficult it is to push the slave piston *further* into its cylinder than the release arm does, you should be able to move it with hand pressure. Be warned, immediately after you have done this the biting point will be closer to the floor than before, and you may not fully disengage (makes a change) it the first time you push the pedal, so pump it a couple of times to get the pistom back to its proper position.
Paul Hunt

Update:
Things became worse tonight...trip Düsseldorf-Frankfurt (150 miles) was without any problems, everything works fine.
But the trip back...first, there was slipping in all gears, except 3rd and 4th with overdrive engaged.
After a while, it was impossible to disengage the o/d, and it seems, that overdrive was engaged in all 4 gears.
At least, serious traffic jams :-(
It was horrible. Tonight, I have drained the oil nd removed the filter, found a lot of mess in it.

@ Mike: Could it be that the clutch lining for the driect drive is gone?

Furthermore, I removed the solenoid, there was plenty of oil in the solenoid housing.
Last attempt tomorrow, new seals for the solenoid, new filter, and if this doesnt help, it seems that we have to pull the engine again. Sometimes I am thinking about a Mazda MX 5 ...sorry, just kidding ;-)

Regards, Andreas
Andreas

Picture of the filter:
http://www.mgdc.de/archiv/bildmaterial/IMG_4576.jpg
Andreas

Sounds like the linings could have disintegrated and clogged up the hydraulic lines as well as causing the slipping.
Paul Hunt

Tonight I found out that Paul is right.
I have had the possibility to examine the overdrive interiors - not because I have disassembled the unit, but because the interiors - or: what was leftover - has left the gearbox through the drain plug.
http://www.mgcars.de/var/leftovers.jpg
By the way...after changing solenoid o-rings and installing a new filter, the overdrive engaged and disengaged perfectly. Bad news: It is nearly impossible to drive in 1st to 4th without overdrive; which is not a real surprise after looking at the photo. The metal element could be the sun wheel circlip, couldn't it? And the other fragment ar parts of the lining, I think.
So I am on the market for an overdrive unit, type LH, 1280 turns/mile for the speedometer...

With greetings from the oil pan,
Andreas

PS: If your german is not so good: the word "BahnCard" on the envelope stands for a special offer for commuters from the german railway system..found it today in my mail :-( AAAAAAAAAAAAARRRRRRRRRRGGGGGGGGGGGGHHHHHHHH!!
Andreas

Yes, Andreas, and a "wett fahrt" is a race( for the toilette?) right? On the bright side, the bahn runs on time, doesn't it ( still?)
Ken R
Ken Rich

"wett fahrt"

Years ago as a child I was playing in pedal cars with some German kids in a simulated street with 'policekids' on point duty and such. Couldn't understand why they kept shouting 'Free fart!!!" at me.
Paul Hunt

And I hope that young Paul had the presence of mind to shout, " No fahrts, please, we're British!"
Ken R.
Ken Rich

Oh, friends, I love these anglo-saxian humour - makes me totally forgotten for what I am here ;-)
But suddenly, "THE PROBLEM" pops up in my mind again :-(
Have ordered a refurbished overdrive today. Does any of the gentlemen has one or two undocumented "tips and tricks" to look after during installation?
I appreciate any help!

"Gute Fahrt!",

Andreas

PS: Please note the little difference between "fart" and "Fahrt", okay? Its not a mistake, there is really a difference, boys!
Andreas

Yes, Andreas, there is a difference, but they both sound the same!

Sorry I can't help with the OD, Best wishes,

Mike
Mike

Andreas - the point was, that at the time I had never heard of 'fahrt', unlike 'fart'. But you are right about the humour, at an Austrian skiing resort we came across an automatic ski-waxing machine labelled 'FAHRT-WAX' or similar - very popular with the Brits as a back-drop. Much like the Americans at Wimbledon with the sign requesting that 'knocking-up' continue for no more than five minutes.

OD ditto.
Paul Hunt

Today we made it - overdrive exchange.
If you follow the manual, there are no problems - pull engine and gearbox, change the o/d, and put the bits back in the car.
The workplace we (my wife Dagmar and me - Dagmar is a skilled craftsmen, a carpenter, and therefore a really helping hand) have rented for this special Saturday opens from 9:00 am to 9:00 pm - time enogh, we thougt.
First problem: How to leave the garage, which is 4 stores under the earth, with only 3rd gear with o/d engaged? You need some patience, some more helping hands, and some drift skills to make it up to streets..
Nevertheless, at 9.15 work begins.
The first pain point was a manifold bolt - just broken.
Then the division of overdrive and gearbox was not so simple...we need a hammer.
The installation of the new overdrive was really something &$%/)&/(&§/&=&§=§&?)(()(/&%§$".
It was impossible to get it on the gearbox - the teeths of the the unidirectional clutch wont go on the gearbox shaft. After some work at the shaft we finally made - two hours later, but without a hammer...
Installation was quite straightforward, some minor problems (remeber the broken manifold bolt), and finally, exactly at 9:00 pm, we were ready...Start the engine - but engine run was...diappointing. The front carburator had decided to produce a little fuel overflow...so, a short discussion with the shop owner, we got our "Go!", pulled the carbs again, cleaned the front one, and:
EVERYTHING WORKS FINE!

Bottomline:
Dagmar and me, everyone has 3 kilos less - so bodybuilding for nothing.
We saved a lot of bucks - overdrive exchange is one of the mayor possibilities for professional workshop to create business.
But its a hard job, and we have had one or two moments very close to capitulation.

Here are some pictures:
http://www.mgcars.de/bilder/trans/Just_delivered_IMG_4591.JPG
http://www.mgcars.de/bilder/trans/New_unit_IMG_4592.JPG
http://www.mgcars.de/bilder/trans/Back_home_again_IMG_4597.JPG
http://www.mgcars.de/bilder/trans/engine_and_gearbox_IMG_4594.JPG
http://www.mgcars.de/bilder/trans/New_unit_installed_IMG_4595.JPG

Regards, Andreas
Andreas

This thread was discussed between 17/02/2002 and 02/03/2002

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