So starting last week my car will make a strange sound every other time I drive it or so... Its like a rough deep tone that you hear under acceleration - kinda raspy. Sometimes after I pull hard through a gear it will go away. Generally seems to do it more when the car is cold, but after going away it will sometimes come back. I did notice the other day that my car has the K&N drop in filters (arent these supposed to be bad for this car) and a tubi exhaust. Wondering if the exhaust could be vibrating on the chassis somewhere as well until it gets up to temp - but wouldnt make sense considering the noise can come back after reaching temp. Anyway, performance doesnt seem to be affected. Wondering if you guys had any ideas... Thanks.
__________________ 2002 Carbon Black/ Caramel lightly modded - SOLD to board member
Biding my time...
One of the things which seems to fail easily is the cam position sensor (CPS). I've never had one go, but off the top of my head I think that it causes the exhaust note to change significantly.
Try a search for CPS - may yield some useful info. If it is that it's a relatively cheap fix - DIY if you are ok with mechanics.
__________________ 2001 M5, Lemans Blue / Silverstone Standard except for a few bits & stereo: 6.5" Focal components, 10" Directed sub, IceLink, JL Audio & Directed amps (hidden). Predator ICE, Stealth bulbs, V1, Roadpilot
1990 Mazda MX-5 (brilliant) 1998 Nissan Primera GT (modded)
I think I have a very similar sound on mine. Usually when cold, before its up to full operating temperature. I have stock air filters but SS x pipe and mufflers.
goes away once warmed up. very strange, like a rubbing sound but definately coming from the center of the car.
Groany, raspy and deep, almost like the airbox fell off the car. (its on there fine) I havent had a chance to check if it is in fact a rub, but it shouldnt be, makes no sense that it would only do it when cold on a rub. And I cant hear it once I open the windows, only in the cabin.
One of the things which seems to fail easily is the cam position sensor (CPS). I've never had one go, but off the top of my head I think that it causes the exhaust note to change significantly.
Try a search for CPS - may yield some useful info. If it is that it's a relatively cheap fix - DIY if you are ok with mechanics.
The first time I had a CPS fail I got out of the car and looked under it as I thought the exhaust system had fallen off. CPS failure gives you more than a loud exhuast note; it also turns on the CES and there is a noticeable loss of power.
Have you guys checked the 2 rubber bushings on the center exhaust? It is part #18207832991 at RealOEM http://www.realoem.com/bmw/showparts...75&hg=18&fg=20. After I got my guibo replaced I noticed that my exhaust sounded louder and there was a slight rattling coming from underneath the center of my car. I noticed that as my car warmed up, the exhaust wasn't as loud, but there was still a rattling, but less frequent. It was more noticeable when going over potholes, whether on the throttle, or just coasting. I went under the car and banged on the exhaust and sure enough, the exhaust would make a clanking around the center exhaust support. It was as if the exhaust was vibrating on the support instead of being supported by the rubber bushings. The exhaust might not have been put back on correctly after the guibo replacement, or I might need new bushings since I hear they wear out after awhile, especially because of the extreme heat from the exhaust. I think the exhaust sounded louder because of the vibration on the center support and as the car heated up it tightened things up a little, thus decreasing vibration. I'm going to take the car back to my indy where I had the work done and have them take a look since the problem started after the guibo repair. A few years ago I also had a similar problem with the heat shield vibrating against the exhaust and it seemed to decrease as the car warmed up as well. Heat shield was fixed and the problem went away. I didn't notice the heat shield contacting the exhaust while I was underneath this time.
Last edited by gmakishima; 25th June 2007 at 19:34.
I had an indy to replace the driveshaft seal of the differential. The guy is experienced with M3:s but was a newbie with M5:s. He didn't pay enough attention to the exhaust center support. Otherwise the craftmanship was very good but he thought the exhaust is supposed to hang loose from the center support not being supported by it. Initially the car was ok but after a night there was a clear rattling noise from around the center support in the morning when I lit her up.
There was no vibration at speed so the driveshaft & shaft installation was ok. However, driving over uneven surfaces caused the rattling noise to appear.
I had the shop and the same guy to have a look at the exhaust. Well, he installed spacers between the body and the connecting support. Now the rattling noise was gone and there is now a clanking noise instead.
So after this concrete examination I have entered into a conclusion that the center support and the exhaust tube have to be installed facing each other. However, the center support above the exhaust tube should probably not be tightened too much, just enough to remove any rattling noise from the exhaust.
It did it to me again this morning... started out fine then about 5 minutes later started again. It doesnt so much sound like a change in the exhaust note as it does the engine pitch and you def feel/ hear some sort of vibration - kinda like a tin can rattling noise. Still not convinced it is a CPS cause I have never had a SES light.
__________________ 2002 Carbon Black/ Caramel lightly modded - SOLD to board member
Biding my time...
I'm having the same issue with the exhaust contacting the connecting support/brace behind the cats. More of a problem cold than hot, and most noticeable at 2000rpm. I just crawled underneath with a deadblow hammer to try and replicate the problem and found the contact to be against the connecting support. The car was fine before I installed the new driveshaft (no rattles), so i must have misaligned the header connections as the rear mufflers bolt into place with no adjustment.
The headers slipped into the collectors very easily, and I didn't see much room for adjustment. But clearly there must be as there is so much pressure on those rubber isolator bushings described above that they are crushed completely flat. I'm going to loosen the collector flang e bolts, put some pressure on the exhaust tubing with a floor jack, and then try to re-tighten them and see if I can adjust their clamping position.
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