Lotus Elan

Engine Mountings 2019

PostPost by: david.g.chapman » Fri Nov 08, 2019 6:55 pm

I have a long standing and slightly irritating issue with my +2.

When the car is cold everything is fine, but once the exhaust side engine mounting heats up on a summers day there can be clutch judder when moving off. I am using the "reinforced" standard mounts with the top void filled in.

The last time I measured the flywheel run-out (some years and 30000 miles ago), it was on the limit at 4 thou. The juddering has not got any worse in that time, and I have fitted a heat shield around the mounting that delays things a bit, but does not really cure it.

I have long thought about fitting the Kelvedon fast road engine mounts (https://kelvedonlotus.co.uk/product/ela ... ne-mounts/), maybe to the exhaust side only, but am concerned about increased vibration for long distance touring.

Does anyone have any thoughts or experiences on this, or can suggest another mount that is just a bit less compliant than my "reinforced" originals?

Dave Chapman.
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PostPost by: nmauduit » Fri Nov 08, 2019 7:27 pm

I'm not sure I get the point of the question : the clutch being solidly tied to the engine/gearbox via the bellhousing, either there is a shudder within that system or not. If one get engine mount harder the shudder will be passed on to the chassis... which I would not think is preferable.
If the mounts (engine, possibly gearbox) are in reasonably good condition and indeed of the harder kind (being filled at the top may not mean they have been made with more rigid rubber and properly bonded), then an inspection of the clutch system may need to be planned.
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PostPost by: david.g.chapman » Fri Nov 08, 2019 8:20 pm

When the car is cold, there is no judder. The exhaust engine mount is the component that warms up the most, the rubber softens and the lack of stiffness allows the judder to resonate through the car. Stiffening the mount may damp down the judder under all conditions.

Think springs and shock absorbers! The engine mount is the shock absorber, and the mass of the chassis and body stops the judder, perhaps.

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PostPost by: Donels » Fri Nov 08, 2019 10:18 pm

I don’t think the problem is the mounting, the problem is what’s causing the juddering. The stiffness of the mounting may change with heat but it’s not the cause of the problem, that sounds like clutch/flywheel. The mounting just responds to it.
It could be the flywheel or the clutch spring fingers. If the clutch is not engaging smoothly it will judder as you describe. I have experienced similar and it was the clutch spring fingers.
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PostPost by: david.g.chapman » Fri Nov 08, 2019 10:38 pm

Maybe that's right. The flywheel run out was on the limit, but the rest of the clutch was new at the time I measured it but I still had the judder when hot.

However, if no one else has had this specific hot problem then the clutch could be the cause and I will live with it until it needs to be changed for a bigger reason.

Cheers,
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PostPost by: Hawksfield » Sat Nov 09, 2019 10:17 am

Hi
Just changed my clutch for the same symtons, the clutch plate although not worn was glazed and with a hard surface.
The clutch was the original from 1971 so was due fòr renewal :oops: :wink:
Regards

John

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PostPost by: alan.barker » Sun Nov 10, 2019 7:55 am

[quote="david.g.chapman"]I have a long standing and slightly irritating issue with my +2.

When the car is cold everything is fine, but once the exhaust side engine mounting heats up on a summers day there can be clutch judder when moving off. I am using the "reinforced" standard mounts with the top void filled in.

The last time I measured the flywheel run-out (some years and 30000 miles ago), it was on the limit at 4 thou. The juddering has not got any worse in that time, and I have fitted a heat shield around the mounting that delays things a bit, but does not really cure it.

I have long thought about fitting the Kelvedon fast road engine mounts (https://kelvedonlotus.co.uk/product/ela ... ne-mounts/), maybe to the exhaust side only, but am concerned about increased vibration for long distance touring.

Does anyone have any thoughts or experiences on this, or can suggest another mount that is just a bit less compliant than my "reinforced" originals?

I had a problem like that on my Elan Sprint. I fixed it by changing the Clutch assembly and getting the Flywheel resurfaced. I found that the surface of the Flywheel was not flat but bowed :?
Now it is perfect. I did put off doing the job for a year or more but finally bit the bullet. It's a good winter job, fit complet Clutch Kit and replace Spigot Bearing. You will be so happy and enjoy .
Alan
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PostPost by: david.g.chapman » Sun Nov 10, 2019 3:15 pm

Oh Alan, you are tempting me. I will think about it.

I might drill a 10mm hole through the exhaust mount first and fill it with a bolt wrapped in rubber for my peace of mind. Then if that doesn't work (highly likely), then its engine out time either this winter or the next!

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PostPost by: Elan45 » Mon Nov 11, 2019 2:39 pm

I've had similar issues when the gearbox mount was getting soft. You haven't mentioned that mount having been replaced, just the two either side of the engine.

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PostPost by: david.g.chapman » Mon Nov 11, 2019 6:50 pm

I have replaced the gearbox mount but it was over 15 years ago. It's worth checking again when I start my winter journeys under the car.

Thanks,

Dave.
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