Very odd clutch problem

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Very odd clutch problem

Postby Asolepius » Thu Dec 04, 2014 9:35 am

I set off down the road this morning after a previous run, so the engine was warmish. After about a mile I was changing up into 3rd when there was a slight clonk which I felt through the pedal, and I could no longer get into gear. The clutch appeared to have failed. The pedal though felt perfectly normal. I tried a few more times to get into gear and was rewarded with the usual terrible crunching noise, in any gear. Fluid up to level. So I sat there for 10 minutes debating whether to call the breakdown service. I made one more try, and everything was back to normal. I drove off, completed my short trip, and got home with no problems. Clutch operated normally. What could have happened? Will it happen again?

This is a 948 block, 1275 diaphragm clutch with stock flywheel drilled to accept it. Ribcase gearbox.
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Re: Very odd clutch problem

Postby Charlie Tolman » Fri Dec 05, 2014 1:13 am

In my Sprite race car, with a 948 engine, aluminum flywheel, and 1275 clutch, I would sometimes have clutch release problems. However, the problem did not "correct itself".
The problem was bent or broken straps that go between the pressure plate and the clutch housing. One or two of three sets of straps would be bent or broken. This might have been caused by sloppy down-shifts with a Hewland geared transmission, at high rpm values.

With a flashlight, look at the clutch through the inspection hole in the tranny bell-housing, from under the car.

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Re: Very odd clutch problem

Postby Asolepius » Wed Dec 10, 2014 6:44 am

Thanks Charlie. I'll have a look as you suggest. But I am wondering whether the driven plate got stuck to the flywheel. I forgot to mention that the clutch does judder slightly when the engine is hot after a fairly long run. I have a rear main bearing oil seal, but only the standard scroll retainer on the gearbox input shaft. So I'm wondering if the clutch is slightly contaminated with oil. As is usual with these engines, there are always oil drips, but never easy to find out from where.
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1959 Sprite, owned since 1978
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Re: Very odd clutch problem

Postby Charlie Tolman » Fri Dec 12, 2014 1:17 am

A remote possibility: The forward portion of the transmission's input shaft became stuck in the crankshaft's pilot bushing, thereby causing the input shaft to spin regardless of the clutch being engaged or not. ??

If the problem occurs again, stop, shut off the engine, and shift into low gear (you might have to "bump" the starter motor a few times to align gears in the transmission).
Then depress the clutch and try to start the engine. What happens ?
Caution: The car might lurch ahead when trying to start the engine.

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Re: Very odd clutch problem

Postby Sprite33 » Fri Dec 12, 2014 1:14 pm

I have a 1098 with a 1275 clutch. I have broken the wire loop that the diaphragm spring pivots on and it gives the same symptoms you describe. I don't see how that could repair itself though. I think newer pressure plates have a different design that eliminates that wire loop to eliminate that problem.

Since you still had pedal pressure, it almost has to be something to do with the pilot bearing or the disc sticking to the flywheel or pressure plate. I know when flywheels are adapted to a different clutch, sometimes the disc does not match the flywheel wear surface and you can get an area of the disc that does not touch the flywheel. This can cause a ridge to form as the friction material wears. This is usually on the inner side of the flywheel and disc. If it gets enough of a ridge fitting down into the flywheel, it could cause a drag that may not release very well. This could get even worse as the clutch disc gets hot and the diameter expands.

Another possibility is a rivet may have come loose and caused an interference that made the disc hang up. While you were trying to get it too work the rivet may have dropped back into place or fallen out of there. This seems not likely but I have seen stranger thing happen. No matter what happened, I think it would be a good idea to drop the transmission to get a good look at it. If it happened once, it will probably happen again.
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Re: Very odd clutch problem

Postby Asolepius » Mon Dec 15, 2014 2:28 pm

The pressure plate was a new one when fitted 3 years ago, so it will be the latest design. The flywheel was in good condition, so I doubt there was enough of a wear ridge to account for this. The flywheel spigot bush was renewed when I rebuilt the engine, but has now done about 25k miles. Yes, it could happen again but I'm finding it difficult to face heaving out the engine now that I've got the steel bonnet back on.
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Re: Very odd clutch problem

Postby admin » Wed Dec 17, 2014 8:46 pm

The "fixing itself" is the tricky part here--the only thing I can think of is what was already mentioned--the pilot bushing seizing to the first motion (input) shaft--but that would be such a long-shot (but it could correct itself).

Got me stumped on that one....
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Re: Very odd clutch problem

Postby Asolepius » Fri Dec 19, 2014 6:36 am

I have just had a look under the car, but it's virtually impossible to see anything useful. The view into the bell housing with the blanking plug out is extremely poor. I can just about see that the release bearing is OK, and the clutch cover is free of contamination. But there's a fair bit of oil in the bottom of the housing and a lot under the chassis. Seems to be coming mainly from the rear main bearing. The clutch has stuck again a couple of times, and releases when I pump the pedal. Occasionally a gear change seems a bit sticky. I think I will have to pull the engine and transmission to fix the leak and see what's going on.

Oh well, I suppose it only takes me about 3 hours to get the whole lot out, and as I'm retired I have the time.....
Les Rose, Salisbury, UK
1959 Sprite, owned since 1978
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Re: Very odd clutch problem

Postby Charlie Tolman » Sat Dec 20, 2014 1:16 am

The method of viewing inside the bell-housing, via the blanking plug hole, is to use a small diameter flashlight, smaller than the plug hole, so that there is no light reflecting off the outside surface of the bell-housing and back into your eyes. I had one with a flexible neck between the bulb housing and the batteries.
Even if one can see inside this volume, there is no guarantee than the problem will be viewable.

A good time to pull the engine, and solve more than one(?) problem.

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Re: Very odd clutch problem

Postby Asolepius » Sat Dec 20, 2014 7:09 am

The main problem is not the light, but the limited view because of the chassis rail. Really needs an endoscope.

But whatever I might see, it can't be fixed with the gearbox in the car. This is a job for after Xmas! I always say that I get more problems with new parts than I do with the original ones :(
Les Rose, Salisbury, UK
1959 Sprite, owned since 1978
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Re: Very odd clutch problem

Postby Asolepius » Sun Mar 01, 2015 12:36 pm

I have at last pulled the engine out and found the problem. The pressure pad that bears on the diaphragm fingers was rattling around because its retainer had fractured. The bits of the latter were jangling about in the space between the clutch and the flywheel. This unit has done less than 10,000 miles. The friction plate and carbon thrust bearing need replacing as well. Things just don't seem to last these days.
Les Rose, Salisbury, UK
1959 Sprite, owned since 1978
Asolepius
1098cc
 
Posts: 489
Joined: Tue Jan 25, 2005 6:50 am
Location: Salisbury, UK

Re: Very odd clutch problem

Postby Charlie Tolman » Mon Mar 02, 2015 1:19 am

I am glad that you have found the problem.
Yes, you are correct about the quality of replacement parts.

Charlie T.
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Re: Very odd clutch problem

Postby Asolepius » Mon Mar 02, 2015 5:16 am

I have ordered a Borg and Beck clutch kit that I found on eBay. Hopefully this will last longer than the unbranded ones that all seem to be made in the far east.

Meanwhile I need to replace the rear main bearing oil seal. This is the kit from the Morris Minor Centre. I can see that the lip seal is leaking, despite having the crank flange sleeved and machined. There's also leakage from the gearbox, and I have made an adapter to install a lip seal for that as well. Might as well change the timing chain while I'm at it - bit of backlash even though it's a duplex. All good fun.
Les Rose, Salisbury, UK
1959 Sprite, owned since 1978
Asolepius
1098cc
 
Posts: 489
Joined: Tue Jan 25, 2005 6:50 am
Location: Salisbury, UK

Re: Very odd clutch problem

Postby Charlie Tolman » Wed Mar 04, 2015 2:06 am

Oil leaking at the front cover of the transmission can be a problem. I attached an O-ring to the front cover, using silicone, and this would work fairly well for a while.
Eventually, I obtained a modified front cover that employed a lip seal, which worked better.
However, it did not eliminate the leak, and I believe that it was because of the less-than-perfect condition of the input shaft surface in the region contacted by the seal.

Charlie T.
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Re: Very odd clutch problem

Postby Asolepius » Wed Mar 18, 2015 12:19 pm

I have installed the new clutch and everything is back together. But it doesn't disengage. The set-up is identical to what I had before, ie 948 master and slave cylinders, 1275 pressure and friction plates, 1275 release bearing. This all worked perfectly when I originally installed the 1275 clutch (ie the one that broke). But this time the pedal travel seems to be less, although the pressure seems the same. I have an adjustable pushrod on the slave and this is adjusted right out to allow full travel of the piston. I didn't need to do this on the previous 1275 clutch. Should I be using a 1275 slave? That I believe will raise the pedal pressure but I can sleeve the master to suit if necessary. The release lever seems to be in the middle of its travel at rest, which I noticed with the previous installation but as I say that worked fine.

Meanwhile I have fitted a lip seal to the gearbox front cover in an aluminium housing that I made on the lathe. New seal fitted to back of engine. If it leaks after this lot I give up!
Les Rose, Salisbury, UK
1959 Sprite, owned since 1978
Asolepius
1098cc
 
Posts: 489
Joined: Tue Jan 25, 2005 6:50 am
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