Lotus Elan

clutch disengagement

PostPost by: seniorchristo » Wed Oct 23, 2019 10:28 pm

About a year ago I replaced both master and slave cylinders with new ones. Recently it has been getting more and more difficult to engage gears both at rest and while driving. The pedal feels normal with only slight play before hydraulic resistance is felt. Nevertheless I bled the system with no visible air. Travel of the clutch fork at the slave cylinder rod is approximately 7/16" (11mm) which I think is normal. I'm leaning towards the clutch disc hanging up on the input shaft but want to explore all possibilities before pulling the engine. Any ideas?
Thanks
Chris
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PostPost by: prezoom » Thu Oct 24, 2019 1:06 am

Once you engage 1st gear, how far off the floor does the pedal come up before the car starts to move?
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PostPost by: seniorchristo » Thu Oct 24, 2019 3:01 am

It may creep slightly but doesn’t really engage until about half way up. Adjustment is also good with about 1/16”+ play at slave pushrod.
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Chris
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PostPost by: Panda » Thu Oct 24, 2019 8:48 pm

With the engine not running, engage 1st gear a few times and note how easy it is to engage. Then with the clutch fully depressed, start the engine and note if the gear is harder to engage. If it is, you have a dragging clutch, possibly rusty splines, warped clutch plate or possibly spigot bearing seizing to clutch shaft. All will require engine removal unfortunately.
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PostPost by: Concrete-crusher » Thu Oct 24, 2019 9:16 pm

It's worth checking there is no movement of the slave cylinder between the gearbox housing and circlip, I needed to shim a couple of mm out of mine

Also the push rod lengths seem to varie on the master cylinder, I ended up using a threaded rod and adjusting it to give full compression of the fluid

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PostPost by: seniorchristo » Thu Oct 24, 2019 9:25 pm

Panda
Gearbox shifts easily in all gears when not running. But has gradually gotten worse when driving. Slave cylinder seems to have proper travel 7/16" (11 mm)? I'm going to remove gaiter and look inside but I fear the worst.
Thanks
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PostPost by: 2cams70 » Fri Oct 25, 2019 4:40 am

Are you sure 11mm at the cylinder is OK? Doesn't sound like much travel to me.
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PostPost by: alanr » Fri Oct 25, 2019 9:24 am

Sounds to me unfortunately like an internal problem and not hydraulics. Maybe pressure plate springs or disc springs broken affecting engagement. Could be anything really and you won't know until you take the engine out to have a look.
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PostPost by: 2cams70 » Fri Oct 25, 2019 9:35 am

I reckon it's hydraulics. 11mm movement of slave cylinder pushrod when pedal is depressed is not enough. Check the clutch hose to see that it's not internally collapsed.
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PostPost by: Craven » Fri Oct 25, 2019 10:12 am

I would try a clutch plate clean up, give a good clutch slip session as there can be build-up of material on the flywheel.
Worth a try.
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PostPost by: seniorchristo » Fri Oct 25, 2019 12:24 pm

Looking at the leverage gained by the fork, movement at the throw out bearing would be about 8 1/2 mm.
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PostPost by: 2cams70 » Fri Oct 25, 2019 12:58 pm

If you can measure the master cylinder pushrod stroke when the clutch pedal is depressed and you know the master cylinder and slave cylinder bore diameters you can calculate what the stroke should be at the slave cylinder.
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PostPost by: david.g.chapman » Fri Oct 25, 2019 5:45 pm

With the car safety on stands and you underneath it, you could remove the release arm boot, shine a light in the bell housing and see what is happening while someone else operates the clutch.

You should be able to see the clutch spring fingers, release bearing, retaining springs etc. and it might show the problem at least.

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PostPost by: seniorchristo » Fri Oct 25, 2019 8:16 pm

Thanks Dave
That's my plan when I return home next week. :)
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PostPost by: Donels » Fri Oct 25, 2019 9:04 pm

If you decide it is the clutch hanging on the splines you could try washing the splines with paraffin before you pull the engine. It will clean and slightly lubricate the splines without making the clutch slip, providing you let it drain and dry for a while before use. It’s worth a try. If you still have to pull the engine, what have you lost?
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