Author Topic: weird rattling noise?? (Read 4424 times)

turbo_negro69 · « **on:** August 09, 2007, 10:54:12 PM »

it's super loud, especially when cold, and it quiets down when hot.
engine speed doesn't matter, it's louder on decel.
it also does it when I have the car in gear and it's moving forward and I step on the brake.
I think it's the flywheel or the pressure plate getting ready to grenade.
I havent had a chance to put it up on the lift and get my co-worker to drive it and have a look at it. but I have heard of the thrust bearings/main bearings being a weak point on M42's and letting the crankshaft move in and out with clutch operation? anybody have a similar problem before? I don't feel like pulling out the damned tranny again!

ak96ss · « **Reply #1 on:** August 10, 2007, 06:26:11 AM »

Catalytic converter honeycomb still intact? That sounds suspiciously like a cat that has gone south to me.

If there is no difference in the noise between clutch engaged and clutch disengaged, I wouldn't think it likely to be the rotating assembly.

turbo_negro69 · « **Reply #2 on:** August 12, 2007, 07:32:10 PM »

Quote from: ak96ss;31348

Catalytic converter honeycomb still intact? That sounds suspiciously like a cat that has gone south to me.

If there is no difference in the noise between clutch engaged and clutch disengaged, I wouldn't think it likely to be the rotating assembly.

I dont think its the CAT, I just had it up on the lift and rapped on the exhaust with a rubber mallet. besides that, it is way too loud to be in the exhaust, and it does it more under a coast load on the engine. Lemme give you an example, say your driving on the freeway and you're in gear and someone cuts you off and you tap on the brake, well thats when it makes the noise, and also when idling in the morning. Clutch engagement doesn't seem to affect the noise. I think its the flywheel itself.

gearheadE30 · « **Reply #3 on:** August 13, 2007, 05:22:10 PM »

The throwout bearing on my parent's M5 did this before it was replaced. Sounds like the same thing to me.

turbo_negro69 · « **Reply #4 on:** August 13, 2007, 11:19:38 PM »

Quote from: gearheadE30;31550

The throwout bearing on my parent's M5 did this before it was replaced. Sounds like the same thing to me.

nope, not the throwout bearing, throwout bearings make noise when you hold the clutch pedal down. I was under the car again today and had my co-worker drive the piss out of the car and I noticed that right under the exhaust (where the manifold meets the rest of the sytem) is rubbing against the swaybar. and the paint is rubbed off the sway bar. I put a piece of rubber hose on the swaybar and we'll see if the noise goes away. If it does it's time for some new engine mounts.

turbo_negro69 · « **Reply #5 on:** August 14, 2007, 10:34:50 PM »

ok, found out it is in fact the motor mounts sagging, causing the exhaust to rub on the sway bar and make that ungodly noise. so now I need to order motor mounts.

fiftytakedowns · « **Reply #6 on:** September 19, 2010, 05:04:22 PM »

howd you test your motor mounts?

Janne · « **Reply #7 on:** September 20, 2010, 10:59:09 AM »

Quote from: fiftytakedowns;96715

howd you test your motor mounts?

You see it if they are bad. Motormount rubbers fuse and stretch, especially exhaust-side.

thebutcher37 · « **Reply #8 on:** September 26, 2010, 08:27:56 PM »

pictures of the said saggy mounts would be cool if ya got em?

maybe some comparison pics to help others judge..... Ive kinda noticed the same feelings/sounds you describe... seems like i might need to put in new motor mounts.