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zob

Knocking / clunking vibration on clutch bite point from standstill

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zob

I've had a good look through previous posts and FAQs to see if anyone else described the same thing I've got but to no avail - apologies if this question is being re-asked!

 

Since i've owned this Mk2f I've noticed a knocking / clunking / stall-like vibration when setting off from a standstill. This usually happened when the car was cold and running rich - just took some extra revs and a longer clutch release and it'd be fine. I just assumed it was a stalling noise as it would always go away once the engine was up to temp and got its oompf back.

 

However today it manifest itself throughout a long drive and so I'm starting to wonder if it isn't something failing slowly. Any advice what to look for would be much appreciated!

 

The noise almost sounds like its on the left hand side of the bay and judging by the conditions needed to make the noise I'm assuming its to do with the clutch. There isn't any noise when changing from 2nd to 3rd or when changing from 1st to second when in a slow roll (like in traffic) - I.e. the noise only happens when the engine speed is high and the drive speed is very low or zero (when the clutch is under the heaviest load?).

 

Its a '93 Mk2f so has an un-adjustable clutch cable. Should I be looking through the inspection plate to check the friction surface thickness first? Has anyone else had this awful clonking before?

 

Thanks for the help!

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caretakerplus

This sounds to me as if it could be caused by worn engine/gearbox mountings - it could even be from the exhaust system and/or its mountings.

 

If you suspect that the clutch is slipping, a quick check is to apply the hand brake, start the engine and engage third gear. Keep the revs at a fast idle and engage the clutch - engine should stall IMMEDIATELY - If there is a delay and the engine keeps running, the clutch is slipping - you may even smell it!

 

Suggest that you check the condition of the mountings before you do much else.

 

Regards

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zob
16 minutes ago, caretakerplus said:

This sounds to me as if it could be caused by worn engine/gearbox mountings - it could even be from the exhaust system and/or its mountings.

 

If you suspect that the clutch is slipping, a quick check is to apply the hand brake, start the engine and engage third gear. Keep the revs at a fast idle and engage the clutch - engine should stall IMMEDIATELY - If there is a delay and the engine keeps running, the clutch is slipping - you may even smell it!

 

Suggest that you check the condition of the mountings before you do much else.

 

Regards

 

Fantastic - thanks for the pointer! I'll have a rummage around and check all the rubbers.

 

 

 

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zob

The engine and gearbox mounts don't look outwardly bad - no cracking or perished rubber. However the gearbox mount can be visibly moved when rocking the gearbox by hand backwards and forwards. You can see the inner bush of the mount move about. Doesn't feel loose - although there is the weight of everything on it so hard to tell.

 

Sounds like a rubber that needs replacing?

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zob

On further inspection my cat isn't actually attached to anything...! Only attached by the middle silencer and the manifold - the two metal straps that are supposed to bolt to the little mount have sheared off and are just hanging. I doubt this is the source of the knocking but its never-the-less slightly concerning...

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zob

Just to be on the safe side (and I doubt they've been replaced for a long time, if ever) I've ordered new rubbers for the left and right mounts and a G60/Rallye bonded bush for the rear gearbox mount as per @dvderlm's recommendation.

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damunk

keep us posted on to what happens when youve sorted dog bone mount

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zob

I exchanged the rear gearbox mount for a G60 one today - only required a little grinding of a thick washer to go over the end, barely any strong-arming involved to get it to fit. Guess I was lucky! One thing I did need to do was unbolt the top of the bracket that connects to the gearbox, loosen the bottom bolt and then swing it down to make space. The old one's tube was rattling around in the rubber so needed changing anyway i expect - looks like the original.

 

Old and new:

https://drive.google.com/open?id=1-W75_Wm9vXbpStX0ksHqkNt8rODug9VA

Installed on the car:

https://drive.google.com/open?id=1-bxOsp_dOD7UPq6CMtPxxNtIDqMYiMT4

 

However the noise was back, and louder than ever - did my best to take a video:

https://drive.google.com/open?id=1-WDaDDEElcCMs3gvsZrjenccVoZRwuXG

 

Frustrated, I had one last look under the car - its funny how sometimes thing just jump out at you: the exhaust clamp after the cat looked far too close to the support strut that runs across the exhaust gulley in the chassis. When tapped with a wrench:

https://drive.google.com/open?id=1-V7TkY68aZMX8h1SLyBEvP9nsHnUaCeD

 

Its the noise! Just a simple vibration against the strut. Unfortunately the nuts on the clamp are totalled so I can't just loosen it and sqing it round - I'll probably have to unbolt the strut, get some boltgrips on the rounded nut and then replace the clamp with a new one.

 

Mystery solved!

 

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