TDI75 Lots of Vibration when Idle

D

davenportmb

Member
My 2001 TDI75 is pretty unhappy at idle. The engine is vibrating a lot and sounds very agricultural, but everything is perfectly normal as soon as the clutch is depressed. There's also a bit of knocking when the car is in motion with a trailing throttle.

Having looked through the forum, these sort of symptoms are normally blamed on a failing DMF which couldn't be the problem here given that it's a TDI75. Does a SMF ever suffer from any wear and require replacement? Or is it likely to be something else like the pressure plate or clutch release bearings? The clutch itself is about four years old and has probably done about 25,000 miles at the very most.
 
When was the brake fluid last changed? I would be more inclined to check all the engine mounts especially the pendulum mount ( dog bone )for wear or perished rubber. What is the idle speed?
 
Could it be noisy gearbox. Bearings ? Foot on the clutch, no noise, would indicate the noise is after the engine clutch assembly's
 
audifan said:
When was the brake fluid last changed? I would be more inclined to check all the engine mounts especially the pendulum mount ( dog bone )for wear or perished rubber. What is the idle speed?
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Brake fluid was replaced about 12 months ago and I'll check out the mounts. The idle speed is roughly 950rpm.
 
steveb said:
Could it be noisy gearbox. Bearings ? Foot on the clutch, no noise, would indicate the noise is after the engine clutch assembly's
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When you say after the clutch assemblies do you mean in the gearbox? I wonder if an gearbox oil change would help the situation at all.
 
Yes, gearbox if it's that noisy an oil change won't help, unless it has no oil at all in which case it won't be in the best of health anyway
 
Could it be the dogbone mount underneath? That could allow excess movement at idle and noises if bushes are badly worn?

Sent from my SM-N960F using Tapatalk
 
Thanks, guys. I'm away this bank holiday weekend but I'll jack the car up soon and take a look and let you know what I find.
 
OK, I'm was due to get the car up on stands this weekend but I've noticed that the noisy idle is totally inconsistent. I can pull up at a set of lights and sometimes the car will sound terrible in neutral, sometimes it won't. And if it does sound terrible, depressing and releasing the clutch whilst still in neutral can sometimes make the idle sound right again.

I think we can rule out the dogbone mount so does it sound like it might be a problem with either the clutch pressure plate or release bearing? Or am I missing something else?

And if it is possibly either of the latter, is it worth just taking it to a garage and getting them to replace the clutch, pressure plate, release bearing and release bearing sleeve in one go? Obviously would rather not have any unnecessary expense - especially when the clutch only has about 20,000 miles on it - but if they've got the gearbox off then does it make sense just to do it all in one go?
 
if there are no knowledgeable members near to help, I would suggest getting a garage you trust to diagnose the fault and go from there.
 
Could still be the alternator clutch. You really need to pin down the exact area the noise is coming from. I would also check for loose heatshields that can vibrate, plastic trim that vibrates especially the lower grille. 20000 is nothing on a clutch so could be a faulty clutch - do you have the receipt for replacing it or know the garage well? Yes if I was pulling the gearbox off I would fit a complete new clutch and all the other needed parts for piece of mind ( and a warranty ).
 
I had a horrible rattle when in neutral and at idle. if I moved the gear stick around slightly it would seem to cure it until I let go of the stick. Anyroad, I had the gearbox oil changed, there were a few metallic deposits in the oil but nothing too alarming, and that sorted it. The following year I had it changed again (about £65 on top of the regular service) to ensure it had a good flush out and it’s improved the shifting too.
 
Is it like a weird churning rattle sound with the clutch up in neutral? Disappears when clutch is slightly depressed? My Tdi does the same - local gearbox specialist suggested it's the springs in the clutch plate rattling. Just watched this on the same subject
 
I recently had the same problem on my A2 and ended up changing the clutch after trying with some simpler repairs first, which solved the problem... Seems our dual mass flywheel had become single mass, and that part is integrated with the clutch.

But especially given that your clutch was recently changed, I'd hope that you didn't have to change it again.

Our problem would disappear when depressing the clutch, or giving a bit of gas.
 
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