Lotus Elan

Stuck clutch by overheating?

PostPost by: S4ever » Mon Jun 19, 2006 6:15 pm

Hello Forum,

This weekend I spent a few laps on a race track trying out new tires and suspension when I suddenly felt a smell of smoke, thought it came from a tire touching the bodywork. I moved the gear to neutral, stopped the car and checked the tires. No problem here.
Trying to get away again I could not get any gear in place. The clutch did not disengage at all.
What had happened?

I got some advice that the clutch might have “burned” and was stuck to the flywheel. Other ideas was overheated hydraulic oil (slave cylinder is very close to the exhaust pipe) or bend clutch arm.

When reading the forum threads about “stuck clutch” and the tricks to get it loose it seems that this always is a result of corrosion because of no use for months or years. I have not been able to found anything about “burning” clutch or clutch getting stuck because of slip / overheating.
The symptom was only the smoke, no metal sound (e.g broken release bearing).

I wonder if a clutch ever can get stuck as above or if the symptom in fact is a typical indication on failed pressure springs / broken / worn clutch plate? (which means that the engine has to come out.....).


Before trying any of the recommended steps to free a stuck clutch I would like your advice if these steps really are the correct actions for me in this situation.
If it is very rare that a clutch can get stuck by “burning” I will probably brake something instead of solve the problem.

I have done some checks:
- The clutch release arm is moving correctly, as far as I can see
- The slack between slave cylinder pushrod and release arm is approx 2 mm
- The slave cylinder does not move, no loose fittings
- The system is bleeded, no air bubbles. The oil is replaced
- When pushing the pedal it feels lighter than before (no pressure from the diaphragm springs?)

Any ideas on what has happened and how to cure the patient?

Thanks in advance

Erik Bernsland
S4 S/E DHC -68
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PostPost by: 1964 S1 » Tue Jun 20, 2006 1:04 am

I'm going to guess the clutch overheated and your pressure plate springs have lost their tension. This happened to me once. What does your car do if you try to start it in gear with the clutch pedal depressed to the floor? If the car lurches forward it's most probably the clutch needing replacement.
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PostPost by: M100 » Tue Jun 20, 2006 8:30 am

The springs in a clutch assembly (pressure plate/clutch cover) clamp the clutch plate to the flywheel. Unless the failure was in the immediate area of the release bearing then spring failure would result in no drive as the clutch friction plate would not be clamped between the pressure plate and the flywheel

If the clutch has stuck to the flywheel/clutch cover then its surface, or that of the flywheel is probably well fried. Removal inspection and replacement is really the only option.

Maintaining the free play at the release arm is essential!
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Elan_Clutch.gif and
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PostPost by: rgh0 » Tue Jun 20, 2006 12:14 pm

I have seen these symptons on race cars ( specifically a Lotus Seven) when a clutch driven plate failed and one of the torsion springs dropped out and jammed between the clutch driven plate and flywheel so it cant be released. I have seen 2 basic types of driven plate design - those with 4 torsion springs and those with 6. The type with 4 springs had this failure and I have seen others with cracks around the spring mount on the way to this failure.

Looks like an engine out job unfortunately

regards
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PostPost by: S4ever » Tue Jun 20, 2006 7:02 pm

Thank you so much for your comments.

With this list and your experiences even a "novice" like me will make the little baby running for years !

"1964 S1" - If I start it in gear with the clutch pedal depressed to the floor the car will jump forward so the clutch is definitely not released.

And it does look as a the clutch is "well fried" as you put it.

I will take the engine out for a closer inspection and needed replacement.

Rohan, as I understand your recommendation is to look for a driven plate with the 6 torsion spring when replacing the old one. Any prefered supplier/brand? Other recommended (clutch) enhancements now when the engine will come out?

Many thanks again!

Regards /Erik


p.s The car handled fantastic until the clutch said goodbye, pure joy!
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PostPost by: rgh0 » Wed Jun 21, 2006 1:07 pm

Both styles are made by Borg and Beck who were the orgional clutch makers. Lotus original fitment was the 6 spring version but the 4 spring version was used on other cars such as some MGB versions I believe and are interchangeable so they end up in Elans.

When replacing the clutch driven plate you should always replace the throw out bearing and flywheel pilot bearing, grind the flywheel face to the correct flatness tolerance and have the pressure plate checked for correct spring loads and grind its surface also to tolerance. If you do all of this the new clutch will work properly for a long time, skip any of the steps and you risk pulling the engine for another go prematurely

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PostPost by: S4ever » Fri Aug 25, 2006 8:46 pm

Hello Forum.

I’d like to give some feedback on “what happened next”.
So what did I find?
Well the driven plate had virtually fragmented into dust and some pieces had got jammed between the clutch driven plate and flywheel. This explains why I couldn’t release the clutch and also why any of the different tricks to release a stuck clutch probably had broken something else.
The suddenly smell of smoke when driving was probably during the moment when the driven plate vanished.

I also found that the spigot bearing had 3 broken rollers and I wonder what can have caused this and if this in turn can have anything to do with the broken clutch (input shaft radial movement?)

An interesting thing with the spigot bearing. It is an INA bearing (http://medias.ina.de/medias/de!hp/;aw-LgB6ibsB7?lang=en) and after some research at the local dealer I found that the reference number on the bearing (33126-2) is a drawing number and not a part number which means that the bearing cannot be supplied by INA dealers. It has to be produced on demand with reference to the drawing number. This is not a problem but the batch must probably be large. I wonder who has ordered the bearings that we now by from our local Lotus spare part shops.
There is an INA stock bearing (HK1516) with very close dimensions to the “original” but when I tested it together with the “original” I could feel a slight difference in radial play on the input shaft so there is obviously an difference (could it be spelled measurement in inch…?) and better not to take any risk


Parts that I replaced:
- New clutch kit from Helix Autosport, a little bit stiffer and stronger than original.
- New stronger release arm
- New release bearing
- New spigot bearing
- New stronger engine mounts
- New exhaust gaskets
- misc. bolts and washers


There have been some discussion on the forum on the best way to remove the engine and I have attached some pictures that show the way I used to sling the engine. The balancer was really a good help when squeezing the engine out/in place.

What you also need is a couple of shortened wrenches, nimble-fingers, shoehorn, jimmy bar and patience, patience, patience ….

There was no trouble to get the engine and gearbox together again, just to be careful with centering the clutch and to put a little grease on the right places (as advised on other places at the forum).

Enjoy your day! /Erik
Attachments
IMG_2256.JPG and
The clutch is no more....
IMG_2264.JPG and
One way to sling the engine....
IMG_2266.JPG and
....and balancing.....
IMG_2284.JPG and
Finally in place....
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