clutch smell - The Unofficial BMW M5 Messageboard (m5board.com)

rennen · 29th November 2001, 01:19

Just curious if any one has had a problem with their clutch constantly smelling like it is burning. Sometimes I'll just be driving at a constant speed, not shifting, and it will start to smell. If anyone has this problem, or a possible solution it would be appreciated.

Thanks.

steve540s · 29th November 2001, 01:21

Sure that it is not your recalled pusher fan?
If you haven't had that replaced i would take it to the dealer.

rennen · 29th November 2001, 01:25

Steve

I purchased the car used, and I never had it replaced. I'll check the old service records though. Was that the reason for the recall?

thanks

greg · 29th November 2001, 01:28

Absolutely positively not right.

A clutch that smells is a clutch that is slipping. and if it is slipping, it doesn't have long to live...

Go get it taken care of...

Sorry

Serge · 29th November 2001, 01:30

I have that problem clutch smell problem too and I am not riding the clutch. I shift like how Greg's videos have showed us(minus the crazy double clutching, can't do that that fast). I can smell burning clutch smell after some city stop-and-go traffic. My clutch is completely out by 800-900 revs on a dead stop pull-away scenerio and I never ride the clutch, what gives??

Sometimes, my car shakes from a dead stop pull away scenerio and the vibrations are similar to those when the car is close to stalling but it isn't because the engine have enough revs(800rpm). It's like the clutch is slipping at 900 rpms. But, if it slips at 900 rpm, why doesn't it slip when i drop the clutch at 6800 from 1st to 2nd? I think my clutch is a screwed-up clutch and I can't reproduce the vibrations consistantly. It happens may be 1 out of 10 dead stop pull aways.

rennen · 29th November 2001, 14:40

Serge

Did your dealer give you any possible causes?

Thanks

Russ · 29th November 2001, 15:17

Quote:

Originally posted by Serge
...my car shakes from a dead stop pull away scenerio and the vibrations are similar to those when the car is close to stalling but it isn't because the engine have enough revs(800rpm

That's referred to as "clutch-chatter"....

A clutch will chatter if the clutch disk gets "glazed". Slipping the clutch under load can heat the disk to high heaven and glazing can occur almost instantaneously. The temps of the disk material can get high enough to actually melt the asbestos surface on the clutch disk itself. Once the pedal is fully released, the clutch disk will cool back down again. But the previously melted regions of the disk can turn into something as hard as glass.

Sometimes a clutch disk only gets glazed part way around... So then, the disk may have regions where it's extremely slippery (i.e. the glazed regions) along with areas of normal friction (i.e. the good original friction regions still left on the disk). When you're letting out the clutch from a start, it's that difference between no friction and friction that causes the clutch to chatter.

Unfortunately, once a disk glazes, your clutch is pretty much on it's way out...

Russ

beemeryzf · 29th November 2001, 15:50

It happened to me last weekend while I was in line to pick up my daughter at a school dance. I have 5500 miles on my 2001 M5 and have never slipped the clutch. I mean I have not slipped it under load or at any substantial RPM. The damn things are made to slip when you engage them if you know what I mean. I have a 540I with a 118,000 miles which has the original clutch in it so I know how to drive one of these things. Anyway I thought the smell was coming from some other car. After leaving the school and driving 10 miles I got out of my car and could still smell the damn thing. Seems to be find now and have not smelled it again but something is wrong here if you ask me.

DrRob · 29th November 2001, 16:34

That pesky clutch problem again. BMW should be forced to issue a clutch recall and build a better mousetrap.

The problem is that not enough units have been sold to muster up enough complaints. If the percentage of M5 clutch complaints applied to sales of 500,000 vehicles over 4 years, let's say, you better believe there would be a recall.

Serge · 30th November 2001, 02:15

Russ, thanks for the explanation. Now I know how to describe the problem as clutch-chatter to my service advisor.
Another question, if my clutch is glazed which causes clutch-chatter, how come the clutch only chatters say 1 out of 10 dead stop pull aways? I have driven the car hard and it never slipped during high rpms and with 4 people in the car. I would imagine it will slip for sure when shifting hard from 1st to 2nd if the clutch is partially glazed...I am lost

.

Russ · 12th December 2001, 03:33

Quote:

Originally posted by Serge
...how come the clutch only chatters say 1 out of 10 dead stop pull aways?...

Serge,

Clutches can slip/chatter due to some mechanical issue(s), pedal timing/technique, or both. One thing for sure, if your clutch has any signs of glazing AND you continue to perform "hot-starts" or "quick-shifts" with the car, I guarantee that it'll eventually fail. Maybe sooner... maybe later... it's all very hard to say...

A clutch can get glazed if you abuse it:
a) high RPM "dump-the-clutch" burn-outs
b) improper rev-matching between shift points (Up or Down shifts)
c) several & repeated poorly executed (slipped) clutch starts in 1st gear (obviously this shouldn't happen if the driver really knows how to properly drive a standard-shift vehicle though)

Once a clutch disk develops any amount of glazing, you might actually find that it fatally slips the first time in one of the upper gears (like 3rd or 4th), not the lower gears. This is because there's actually less mechanical (torsional) advantage being provided by the upper gears of the transmission, and, as a result, more stress across the clutch facing.. Going to WOT and applying maximum engine torque/HP into the clutch assembly creates tremendous rotational forces across the clutch facing... and it's worst in these upper gears.

The lower gears (like 1st & 2nd) however offer more gear reduction than the top gears. This higher gear reduction actually takes off some of the torsional (rotational) stress from the clutch facing. And it's this higher gear reduction that makes it easy to pull the vehicle out from a dead stop in 1st gear.

Now, I suppose it's possible that there's another mechanical failure that may cause clutch chatter: It's (remotely) possible that one of the springs inside the clutch disk is actually broken. These springs are there to provide a torsional cushion during clutch take up (i.e. they smooth out the clutch disk/flywheel/pressure plate engagement). If one of the clutch disk springs break, you can end up with loose (broken) pieces floating around inside the clutch area (not good!). You usually get some bad noises/sounds in/around the clutch pedal if that happens. A clutch disk with a broken take-up spring will have more tendency to wind-up during clutch release and might even make a "bottoming" noise since there's less spring force left to take up the engine torque.

The springs inside the clutch disk can break because of abuse, but I've seen them fail prematurely due to manufacturing flaws, or even fail just because the clutch disk assembly was cheap (i.e. low-quality) (not very likely with an OEM part).

Glazed disk or broken spring: either one sucks 'cause you have to go inside to the clutch assembly to do the inspection/repair.

But... for now, try to enjoy your car! If there's no strange noises coming from the clutch, keep driving it. Practice on getting your clutch releases nice, smooth, and consistent.

If the clutch does eventually fail, have your dealer replace it.

Hope this helps!

Russ

alpywhite · 12th December 2001, 03:55

Serge, I get clutch shatter in stop-and-go on the Lions Gate Bridge all the time...