mx5cartalk.com

So, after changing the clutch, my little NA6a has developed a nasty buzzing .....

Symptoms - throttle up the revs in gear - not much noise ....
Throttle off at around 60-80 klm nasty buzzing noise .... goes away with clutch - but not straight away .. it almost seems to be related to engine vibration rather than anything else ...

I have done the following

Header heat shield - removed
Down-pipe heat shield - removed
Cat heat shield - removed
Clutch throwout arm - adjusted until there was very little movement (clutch pedal feels much nicer now too!)
So far the buzz is still there

The only thing i can think of is that it is related to the exhaust - i did break the down-pipe bracket when i was removing it (and didn't put it back - i know that this is bad long-term ...but ...)

the only other option i have is that maybe it is related to the clutch springs / throwout bearing .... but that would make noise on the up and down throttle regardless of RPM in my mind ....

Next thing for me to try is to make a new down-pipe bracket and see if that helps (will have to be next weekend now ... )

Ideas ?

J

Is it rattling or buzzing? All the items you removed would suggest metal movement which most likely means rattling.

But if it's a buzzing noise, the one that I've experienced in my car was caused by an over tightened power steering belt. A quick loosening of the pulley fixed the problem.

No, you are right Hammer - it is a high-frequency rattling ....

I'm 99% convinced that its to do withthe exhaust, but 'genle tapping' with a rubber mallet doesnt really show anything . . . maybe a light rattle coming from somewhere up the back ...

Mrs KazJim suggests that its exhasut too ....(Does that mean that i get to spend my ruddies on a new system ? )

Thanks
J

Sort of offtopic: But did you feel any difference in Cabin heat when removing the downpipe and cat heat shields?

The clutch on my first 5 was changed by a garage and soon after I too heard a buzz/high frequency rattle. It sounded like it was coming from under the car, like the exhaust. It turned out to be a bracket in the engine bay. From memory the backet supported the main power lead from the battery into the engine bay. The bracket should have been attached to the gear box bell housing by one of the bolts that is removed in order to get at the clutch. The bracket was rubbing against the firewall, and thereby causing the noise. Attached the bracket and the noise was gone.

The other possibility is more expensive to fix. In a couple of my 5s (NA6) I had noticed a strange sound after the clutchs were changed. I checked the bracket as mentioned above, no luck. It only appeared when taking the foot of the throttle, with the clutch engaged. It only went away when I replaced the standard diff from my current 5 (NA6) with a LSD from a 2001 model. This has been reported by a number of people, including Stan the Man. It is believed to be caused by 'lash' in the drive train. The later model diffs have a hard rubber plate where the tail shaft attaches to the diff. This seems to absorb the 'lash' and the noise is gone. Don't know why this seems to only appear after a clutch change, but it can be a pain.

Hope this helps.

J

Did the exhaust get knocked about abit when the clutch was changed?
Is the rattling from the front or back of the car? (or is it hard to tell?)

My friend had both a clutch buzz and exhaust buzz on his car and it drove him to distraction (albeit on an S2000)
The exhaust buzz ended up being a collapse of the structure inside the resonator, but I'm guessing this can happen in the can of the muffler as well?

The clutch on my first 5 was changed by a garage and soon after I too heard a buzz/high frequency rattle. It sounded like it was coming from under the car, like the exhaust. It turned out to be a bracket in the engine bay. From memory the backet supported the main power lead from the battery into the engine bay. The bracket should have been attached to the gear box bell housing by one of the bolts that is removed in order to get at the clutch. The bracket was rubbing against the firewall, and thereby causing the noise. Attached the bracket and the noise was gone.

I had exactly the same problem the first time the dealer changed the clutch in the SP.

Ok, narrowing it down slowly ....

Made a bracket for the down-pipe this morning ...

No difference ....

So, its time to start looking at the rear section of the exhaust, and any pipes / brackets around the engine ....

After that, I'll just get to love it and hope that it's the new 'cool sound' of 2009 - like BOVs were in 2004 !

Cheers
J

There is a remote possibility that it could be the clutch release lever vibrating against the slave cylinder actuator/push rod end. Try a dab of grease where the two touch and see if it helps.

You might be onto something with that, I adjusted the pedal a little to take up the slack, but there is still a little movement ....

I cant find any speds of the clearance at this point, should it be a firm touch, or a nice gap of about 0.040" ?

My best guess would be touching, with a little tiny bit of pre-load ....

a way to test would be to place a light spring against the leverand going to the slave . sort of hold them together ....

Hmmm, might give it a try ....

Cheers

J

kazjim wrote:You might be onto something with that, I adjusted the pedal a little to take up the slack, but there is still a little movement ....

What you're doing there is adjusting the pedal free play. You should have 0.6mm - 3.1mm free play at the pedal.
You don't want zero - that can cause premature clutch wear.

However, I'm talking about under the car - where the slave cylinder rod meets the clutch release lever.

kazjim wrote:So, its time to start looking at the rear section of the exhaust...

Hope you found the annoying buzz, but if you haven't then the heat shield covering the mid-rear bullet muffler/ pipe of the na6 exhaust system was the source of a metalic zinging sound at starting around 3k rpm from memory.