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MG MGB Technical - New Clutch slipping

I have a new clutch that has about 3000 miles on it. I have replaced the rear main oil seal and the trans oil seal.
-Now here is the problem. The clutch has a tendancy to slip quite frequently. It has a heavy duty pressure plate with a standard clutch disc. When the car is first cranked the clutch works well. After the engine has been running for about 20 minutes it begins to slip terribly. It doesn't matter what gear I am in. After an hour or so it will begin to work correctly. When the clutch is dumped it will not bark the tires, the clutch simply slips, same for hard shifts into second(tires are 157/75/14). This is frustrating me quite a bit. If anybody can provide an answer it woud be greatly appreciated.
-On another note, has anybody cross-referenced the MG clutch and pressure plate to a modern vehicle?
Thanks a lot
-Robert
Robert

Robert, You should read my current thread called, "Clutch Slipping When Cold - Why?", especially the comments by Paul Hunt. Also does you transmission have an OD. Your problems may be related to this as with my car. Good luck.
Robert Browning

My car is equiped with O/D. However I am inclined not to think it is the O/D. Reason being is that the overdrive works fine and the problem will occur in first, second, third, fourth, and fourth O/D. The trans does have 138,000 miles on it. The O/D lockout does work, I can make the slippage occur on level ground or a hill, overdrive enguaged or not. The slave cylinder, hose, and master cylinder were rebuilt/replaced within the last 3 years. The problem seems to happen whenever it wants to, but it is generaly as I am just entering the interstate after driving through town(about 10-15 minutes). As for fluid, I am using ATF. Yea, thats odd- but ATF is used to clean out the trans, and I have been told there is no problem with using it all the time- the trans seems to make less noise with it also.
Robert

Does it also slip in reverse?
Chris at Octarine Services

Robert. How did you prepare the clutch before installing. About a year ago, I purchased several clutch kits for my projected projects. All were the new manufacture (I believe it was Phoenix who bought out Borg and Beck and is producing clutches under that brand name) and packed in the white boxes. The pressure plates had preservative oil on them and the clutch plates were in partial contact with the pressure plate in the boxes. The throwout bearings were lightly wrapped and bouncing around in the boxes. One bearing, out of three, was so badly damaged it had to be replaced as unusable.

When I install these sets, I clean the preservative off of the pressure plate's mating surface and clean the clutch plate with brake cleaner to get off any oil that may cause slipping. If that had not been done, I would have expected the clutch to begin slipping soon after installation due to contaminated lining of the clutch plate and the amount of preservative on the pressure plate. Was your set packaged like this and did you clean it before installing? Les
Les Bengtson

I have not noticed any slippage in reverse. I very rarely let the clutch all the way out in reverse, and I usualy don't back up more than the length of the car.

The pressure plate was cleaned with lacquer thinner prior to installing. I never dreamed that anybody would put oil on the clutch disc so it was not cleaned.
Robert

Well, try it out properly in reverse - if it slips in forward gears but not in reverse - it is definitely the OD unit cone clutch that is slipping.
Chris at Octarine Services

Well, Good news I guess, I went for a drive today and the clutch began to slip, so I pulled off into a parking lot and tested the slipping in reverse- the slippage is just as bad in reverse as in first and second gear.
The problem seems to get worse as the clutch heats up. Any suggestions? Is it possible to spray something like brake cleaner through the hole for the fork for the throwout bearing and clean the disk and pressure plate or is that out of the question?
Thanks
Robert

Robert. The slipping creates a glaze on the surface of the clutch plate. This will continue to allow the clutch to slip even if you could get any contaminate off using the procedures you describe. In my experience, you are going to have to pull the engine and tranny, seperate them and physically examine what you have. Then, everything should be cleaned thoroughly and a decision made as to the clutch plate. If it is only glazed and not significantly contaminated, the glaze can be removed with some sandpaper and the clutch plate reused. If it is contaminated with oil, it definitely needs to be replaced. Make sure you clean the pressure plate and get all of the preservative oil off of it before re-installing it. Also a good idea to inspect it and make sure it is in good condition before re-using it. I always keep at least one spare clutch kit as part of my spare parts in the garage. This might be worth considering so that, if any of the parts you are currently running need to be replaced, you can do so immediately without having to wait for parts to arrive. Les
Les Bengtson

Carbon tetrachloride or MEK, very nasty stuff, don't let it touch you or breath any. Probably now illegal. We used to spray it on problem clutches as a temporary fix.

Les is right, it will have to come out and be properly attended to. I'd suggest a new disc as I have tried to economize and save a bad one without a good result. The disc is cheap compared to the labor involved.

Good Luck
Edd Weninger

yea, see, that is the problem, the labor. If I want this fixed I am the one who pulls out the engine and does all the work. While I have done it twice before, it was just august when I last pulled the engine, only 3000 miles ago, I can't say I am realy ready to do it again.
Perhaps I am coming up on Christmas break for a reason.
Robert

Robert. From the "Perhaps I am coming up on Christmas break for a reason" and from the fact that you can write in an articulate manner, I assume you are a college student. If such is so, do not despair. The change is packaging, which allowed the preservative oil on the pressure plate to contaminate the clutch lining, is not well known. I mentioned this problem to both Moss and to Brit-Tek. Bob Ford, at Brit-Tek responded by noting that they were going to take steps to try to handle the problem. I do not remember Moss responding. Yes, this is a royal pain in the neck. But, by pulling the engine and tranny, you can see what the exact problem is and correct it. Life is about learning and lessons learned early stick with us for the rest of our lives. If, however, you are a college professor, you should have known better. Professor Bengtson
Les Bengtson

You are correct Professor Bengtson, I am in college. A freshman at Winthrop University in South Carolina.
Hopefuly I will get the engine in and out this time without too much fuss. Last time I pulled the engine I had the exhaust manifold studs ring off and the two bottom bolts that hold the trans to the engine stripped and the nut would not back off. I also replaced the engine and trans mounts, that is quite an experience.
Thanks to all who have responded for your help.
--Robert
Robert

Would it be possible to scour the disk and rub the flywheel and pressure plate with heavy sandpaper to increase friction and prevent this glazing from reoccuring?
Also, can I reuse my disk or is the general consensus to replace it? The presure plate is relativly new- does it need to get replaced also?
Thanks a lot
Robert

Robert. We have all been there. I bought my first Brit Sports Car, a 61 A-H Sprite Mark II, in 1968 using the money my parents gave me when I graduated from high school. One thing I have learned over the years is that there are always problems and you will always make mistakes. For the most part, I have been able to learn from the mistakes, which help to contain the problems. Whatever you do, do not give up on the MG. Yes, they can be a pain in the neck, not to mention the wallet, but they are very good automobiles. What you learn today will last you your entire life. Last weekend, my daughter, who is a junior at University of Arizona, called me to tell me that she had been able to diagnose a problem for anothter person in her apartment complex. She had been able to find the root cause of a drivablilty problem which was due to a loose distributor cap. She learned to drive on a 77 MGB and still owns that car. My mother had to be hospitalized and I had to go back to Florida for many weeks. This was at the same time that her younger sister, Maria, got her learner's permit. Theresa took her sister out driving, teaching Maria the things that I had taught Theresa, but could not teach Maria. Much could be said about "family dynamics" and other such BS. Bottom line is that Theresa learned to drive on an MGB, took pride in what she learned, and taught her sister to drive in the same manner.

Recently, that teaching was tested in that most complex of tests. Maria was rear ended, in her Miata (she is too short to drive an MGB) and survived. Thus, the lessons taught to her allowed her to deal with an exteme situation. She knew she was about to be hit by someone in a large pick up truck, but decided, in an instant, that to try to avoid being hit would result in loss of control of her car. She maintained control after impact and is here today to bitch about her car still not being back from the repair shop. The next week, the exact same situation happened, but with an untrained driver being hit. That driver is not able to complain because she is dead.

Enjoy your MGB. Put up with the minor problems that it entails. You are one of the fortunate ones who will be able to pontificate, many years hence, to the relative newcomers to our world. Good luck on the final exams.

By the way, I am only "Professor Bengtson" to other professors and other assorted assholes. To you, I am Les. Les
Les Bengtson

Les how bad was your disc soiled? I've seen p plates covered in grease out of the box but never on the disc. One story comes to mind , whereas a young friend needed a clutch in his 911, he wanted to do it himself and to make the story short he did not clean the p plate and when he started the Porsche the clutch did not slip rather it would not release takeing it apart we found it was glued together, young man that he was[read poor] he cleaned the p plate, lightly sanded the disc and put it back in it worked like a champ. With this in mind ,I'd look for more then shipping soil,I,d look for an oil leak, from the amount of slipage you write of, Robert,it seems like oil. RIC
R E L Lloyd

Well, I have had my father put in an order for a new Pressure plate and disk. The B is here to stay as long as I have anything to do with it. The car was bought new- a special order in 1969 by my Uncle for a Roadster with Am radio, wire wheels, and overdrive. My father bought the car in 1990, I learned to drive in that car in 1999 and have been driving it ever since. I drove it for the four years I was in highschool, it is now at college.
Last night I went for a drive, about 20 miles from the school I lost cylinder 3 way out in the country. I pulled over thinking I had a fouled plug, but as I stood there looking at the engine idleing rough and missing on cyl 3(the #3 plug would fire when removed from the engine) the engine shut off and would not restart. I checked my fuel pressure, float bowls everything I could think of. I have electronic ignition and figured out that I could get the coil to fire if I got the reluctor wheel in the right position to trip the sensors. So playing with the reluctor wheel and holding the coil lead to the block I could get a 1 inch spark. But hook up everything to the distributer and I got no spark to the plugs, I figured out what carbon tracking was last night. Took me an hour and a half, much of it spent in the dark.
I have had several offers to buy the car(I can't sell it- it is my father's) and have not considered any of them even remotely- last year the VW dealership asked to buy it!
I won't give up on it, do not worry about that.I will stop driving it eventualy when my Chevrolet smallblock powered BGT gets going.
thanks all for your help
--Robert
Robert

RIC. Do not know what you mean by "soil". If you mean did the preservative oil from the pressure plate get onto the clutch plate, the answer is yes. When unused, this contamination can be removed by an application of brake cleaner, TCE or other solvent. Whether the clutch plate may be sanded, then de-greased, I do not know. I have never tried it before. Some people feel that a leaking rear main oil seal or a transmission input seal can contaminate the clutch plate (driven plate). That is not my experience. While I do replace the rear main oil seal and the transmission input seal on cars that I have apart, but do not know the history of, my experience suggests that a leaking rear main oil seal is behind the flywheel. Leaking oil from the rear main, unless it gushes, does not make its way to the pressure plate and clutch plate. When the input shaft seal is leaking on the tranny, the oil moves forward and encounters the pressure plate, which throws it into the bell housing. Once again, this does not, except very rarely, contaminate the clutch plate.

Thus, my experience is that, with the recent clutch kits, the most likely cause of contamination is the poor packaging of the clutch and pressure plates. My experience also indicates that a through cleaning with brake cleaner, before installing the parts, will prevent the problems that have been described.

The situation you describe, with the Porsche, is similar to what I have encounted in the past. I have been able to clean up old parts, sand the glazed clutch plates or brake parts, and they have worked well. But, I cannot guarantee the results will be good. They worked for your fiend and they have worked for me. Whether they would work for someone else is a judgement call. If it were my car, I would clean, sand and reuse the parts. If it were my daughter's car I would clean and replace all the parts. Les

Les Bengtson

Robert. I would remove the engine and tranny and see what I have to work with. My opinion is that you should be able to deglaze the clutch plate and clean the pressure plate and re-assemble. That is what I would do if it were my car. But, I have two MGs and a truck to drive. Thus, if I make a mistake, it is an "oh darn" and I drive one of the other vehicles. In your case, it may mean the loss of all transportation. So, a new clutch assembly is not a bad thing to have on hand. If you find the current parts may be cleaned, deglazed and reused, you have a new clutch assembly on hand for the future. If you find parts are bad, you can replace them with new parts. Remember to clean the new pressure plate to remove the preservative oils and, if necessary, use some brake cleaner to remove any contaminates which may be on the clutch plate. Les
Les Bengtson

Along with everything else, don't forget to clean the flywheel also. I prefer MEK (cheap at Home Depot) to Les's brake cleaner but that's just presonal preference.

BTW, I would use the new disc if you have one. Your pressure plate is probably OK if cleaned well. The material on the disc is capable of absorbing oil and while scuffing it may make it look OK, it is quite possible that oil will again come to the surface.

Good luck,
Edd Weninger

Did you check for free-play in the hydraulics by seeing if you can push the slave piston back into its cylinder a little further? Lack of free-play *will* cause clutch slip.
Paul Hunt

This thread was discussed between 14/12/2003 and 17/12/2003

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