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MG MGA - seized master cylinder pistons

Hi Folks. Whilst cleaning my basement, I happened to find a long forgotten MGA master cylinder unit. It seems to be complete, but the pistons are thoroughly seized in their bores. I put the master cylinder in a pot of almost boiling water for a couple of hours, and both pistons now at least will budge when a bolt is inserted into the pistons, and rapped smartly with a hammer. The pistons however are still awfully tight. Compressed air at the brake and clutch pipe openings did not budge the pistons. I am wondering if anyone has any suggestions to remove the stick pistons? Dynamite is not an acceptable suggestion! Cheers! Glenn
Glenn

Fine threaded bolt in the outlet port. Drill and tap the bolt to acceps a grease fitting. Pump the piston out with pressure from a grease gun. See here: http://mgaguru.com/mgtech/tools/ts203.htm
Barney Gaylord

Run a line from a bleed screw port on your car to the MC outlet and pump away! Don't let the fluid in the car drop too far. Grease in brake parts is evil and hard to get out. If the pistons are now down in the bores, clean the bore as much as possible before you force the pistons out.
FRM
FR Millmore

Hi Barney and FR. Thanks for the tips. Questions though: Both brake and clutch master cylinder bores have feed holes leading to the reservoir. Do those feed holes need to be plugged in order to build and maintain pressure in both cylinders? Thanks! GLenn
Glenn

Without plugging the feed ports, you won't be able to push the pistons back any more than to their rest positions. But, I assume they are now "down" a bit, and if you can push them back, things should get easier. You can then work them back & forth. Don't really know how to plug the ports either, though on this cylinder you could clamp a plate over the reservoir top and pressurize both bores through one output port. Remember that the piston(s) are likely to come out with considerable force!
FRM
FR Millmore

Sometimes all it takes is a sharp rap on the bench to get some movement. The cylinder stops, the piston wants to keep going. lather, rinse, repeat...
Tom

I had a similar problem with the brake side of my M/C. I was able to free it by inserting a flat screwdriver into the piston with enough of an interference fit that I was able to rotate the piston with the screwdriver. It eventually freed up. I had my grease gun ready in the event this had not worked.

When you finally do get the pistons out, be extra careful when fitting new seals on them. It may look like the seal is seated properly, but it isn't until it has the same cross section configuation of an uninstalled seal. An improperly installed piston seal will result in the piston sticking in the M/C bore and will drive you to drink. I fought that problem for several days and thanks to a lot of suggestions from this board, I finally "got it." In the meantime, I got so good at removing/installing the M/C I considered adding that skill to my resume.

Barney's web site was extemely helpful in this process as well.

Good luck and let us all know how you made out.

Don Carlberg
D. R. Carlberg

As a last resort, I pushed my pistons in as far as I could, honed out the bore to clean the rust, used lots of light oil, and whacked the face of the M/C with a board, as I held the M/C with the bores pointed down. Striking the M/C with the board caused the M/C to travel up and the pistons to go down, and finally come out. I also applied heat with a heat gun, which helped to expand the M/C, but not the pistons.
I did this as a last resort, because the M/C had been sitting in the car for 20 years and I really didn't think it would do any good. But it did!
Cleve

Hi folks Re: plugging the ports: could the port holes be drilled and tapped to accept short machine screws? Would this adequately plug the ports to allow the pistons to be fully blown out the cylinders? The pistons in this master cylinder are extremely tight. It takes a hammer and bolt, and heavy blows to even budge the pistons, although they both do move. I suspect the bores in the casting will be pitted, but the casting could be sleeved. Anyone know who sleeves master cylinders in stainless steel inexpensively? Thanks. Glenn
Glenn

Glenn,
On several occassions I have had success in removing stuck pistons by threading a bolt into the opening of the piston. I'm pretty sure I used a UNF thread, but I can't remember what size. You don't have to tap the piston because the hole is just the right size that the thread will "bite". You can then grab the head of the bolt (use your favorite method) and pull the piston out.
Clean the bore and hone it. I've had several MC's like you describe that clean up perfectly fine with out needing a sleeve.
Oh, if you do go for sleeves, I'd recommend staying away from Apple.
Cheers,
Gerry
G T Foster

Glenn:

You might consider stopping before you damage the unit for a core. Apple Hydraulics and others listed in NAMGAR will resleeve you unit, provided they receive a good core in exchange. If you damage the threads or somehow distort the body, you might render the unit worthless as a core. Certainly, it is a learning exercise to disassemble a frozen unit, but if your ultimate goal is to have the unit resleeved, let the rebuild shop do the heavy lifting. They are used to it and will quickly tell you if your unit can be rebuilt.

My 2 cents...

Steve
Steve Brandt

Hi folks. I cut the end off an old brake hose, then drilled and tapped it to accept a grease fitting. The adapter was then screwed into the master cylinder outlet(s) Several pumps of the grease gun on each cylinder pushed the pistons to the tops of the bores. (hydraulic pressure never ceases to amaze me with it's power) A bolt threaded into each piston then allowed attachment of vise grips, and piston removal. Im glad I wore safetly glasses, since grease squirted out of the reservoir ports, and landed square on my lenses!) I have not cleaned the cylinders sufficiently to tell if they are badly pitted or not, but the master cylinder is finally disassembled, and without using dynamite! The master cylinder is soaking in solvent overnight, and will hopefully dissolve and remove all the grease. Thanks for the kind assistance folks! As usual, this forum, and it's members are extremely helpful with all manner of weird problems that only an MGA could provide! cheers! Glenn
Glenn

I just sent a fairly rare slave cylinder to a guy who had stripped threads on the inlet. His shop that was going to restore it said to not do a thing, they would rather handle it all. So Steve's advice is right on, if you're going to sleeve it.
Tom

Hi Steve and Tom. I generally do all my own work, or as much as I can do with the tools and considerable stubborn streak that I possess. Call me a wingnut, but I take ALL work on my MGA as a personal challenge and ongoing learning experience. I therefore balk at turning over any type of overhaul challenge to anyone else, unless it is clearly outside my tool inventory, ability to do the work, or ability to learn how to do the work. The only work I have been unable to do thus far is machine shop work, and bucket seat reupholstery, which I farmed out to local shops. Virtually all other work that has ever been done on my car has been self completed, or completed with friend's assistance. My car has NEVER been inside an automotive repair shop, except for a required safety inspection! My MGA is truly home grown! I have found that if one doesnt try, one never finds out how much one is actually capable of! When I first restored my MGA, over 25 years ago, I didnt know very much about MGA's or auto repairs geerally. But I wanted to learn, and found that hands on experience was generally a good teacher. My sole source of information back in 1980, was a beat up factory manual. From reading that book, making sketches of disassembly, and using my own (twisted) logic, I was somehow able to completely strip, and thoroughly rebuild my MGA into a running vehicle again! Amazingly, I did the entire job in only 14 months, start to finish! (young and foolish) More amazingly, I put my MGA that had been converted into a (very butchered) V-8 drag racer, back to stock configuration at the same time! Of course this was long before the Internet, digital cameras, readily available parts, or restoration manuals! Simply obtaining parts back then for my "orphan" was a major and very time consuming effort! Today those resources are easily available, and online forums such as this are a goldmine of technical advice and support. So thanks to everyone who gives technical advice and helps me keep my MGA running. Cheers! Glenn
Glenn

Glenn,
I'm with you on this one. Besides the satisfaction and confidence that comes from doing it yourself comes the peace of mind from knowing how and what was done. I've seen the butchers', ummmm, experts' work and have been (for the most part) unimpressed. Outside of precision machine work, there's very little the skilled home mechanic can't fix on an MGA.

Cheers, and keep 'em on the road.....
GTF
G T Foster

I respect and envy you guys who never have to turn to "professionals" for help. Unfortunately, while I am a decent "wrench", I also have a 50+ hour a week job, and at this age (60, and moving fast) I have to, now and then, outsource to keep things moving at a pace I think I need. Along the way I've suffered from some shoddy work (see some of my earlier posts about my engine "rebuild" done by Sports Car Haven in St. James, NY). Nevertheless I continue to look for good help.

My recent carb rebuild, done by Joe Curto, is a good example of a positive experience. Joe was recommended to me by Cecilia of Scarborough Faire, and he is one of the "old school" who takes great pride in his work.

I took them off, sent them to Joe over the Christmas holiday, and got them back a couple of weeks later in beautful shape. I had the pleasure of putting them back in place and now have a running car again, This timeframe is possibly a month sooner than if I had to do the work myself, between ordering the parts, watching the video, reading the manuals, etc.

I guess my message is, please don't "look down" upon us who have to get others involved, as it is because we believe it gives us more driving time in the vehicle, especially in the weather we can enjoy it. My current motivation is to make the Key West Regional, and any other roadblocks I run into will be a trade-off of how much time I have vs. "outsourcing" to those who specialize in what I need.

By the way, the advice of all of you on this BBS, including Glenn, have also saved me many an hour of fruitless, frustrating labor on this 44+ yr-old vehicle that continues to bring us back to when we were young!

Thanks - Ken

Ken Doris

Hi Ken. I suspect many other people also have problems with time limitations, due to busy home or work schedules. I don't think anyone can or would fault folks with insufficient time, for having to farm out MG repair work. Similarly, many people are perhaps not entirely comfortable doing particular types of mechanical or repair chores, or dont have the specialized tools to do the work. So again, it is quite understandable that many folks really have no other choice but to have work done on their vehicles. MGA's are getting to be a fairly rare sight on our streets, and I certainly endorse doing whatever it takes to keep these beautiful and fun cars running, and on the road, where they belong. My concern is that over time, repairing these obsolete vehicles will perhaps become a dying art, and that fewer real experts will exist, that can actually fix these cars,and fix them correctly! Cheers. GLenn
Glenn

I too certainly did not mean to imply there is any shame is out sourcing repairs. I sent my carbs to a gentleman in New Hampshire to get the throttle shafts replaced. Its mostly a matter of finding a mechanic you can trust. When the guy at the garage where I go for safety inspections can't figure out how to start it, has never seen an SU or worked on a distributor with points, etc, etc, no way am I letting him put a wrench on it. This is my baby were talking about.....:)

Ken, I envy you going to Key West. That is one regional I want to attend and hope they continue to hold. However, this spring I'll be spraying paint and frantically preparing for MG2006 in June. Yes, there is a penalty for "doing it yourself".

Regards,
GTF
G T Foster

GTF - I was in a similar position last year, trying to get ours ready for GT-30 in Mackinaw, wishing I could make the first Key West Regional but knowing it was way too soon in the restoration.

Of course, the fact I had the engine rebuilt by a "professional" led to missing Mackinaw because the rebuilt engine only lasted 55 miles before bending a valve - re-enforcing your point about finding trustworthy help.

Finally had it in shape to do a 1000 mile round trip to Watkins Glen in September after finding reliable help to rebuild the head (Rich Mooers, who owns a '60 MGA 1600 and a '55 Magnette and is the head mechanic at Tyrolean Motor Works in Northport, NY).

- Ken
Ken Doris

This thread was discussed between 31/01/2006 and 03/02/2006

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