Greetings. I wish my first post was under better circumstances but it's not. I recently picked up a 91 M5 with 68k. Beautiful. I took it to the dealership today to give the complete once over. They looked over it recomended adjusting a rough idle and replacing the shims. I'm fine with that. Today when I bring it home (I'm around 55 miles from the dealership) I hear a very odd sound.
I know describing sounds is almost useless but I'll do the best that I can. It is kind of like a low rattling/burring sound. It isn't high pitched, but doesn't have any exhaust tone to it. It doesn't really sound like a belt either. It is kind of like a marble rolling/getting stuck sound. I can hear it best when I put my head next to the wheel well.
I know it could probably be a bunch of things but I would like to know if there is anyplace I should look. Should I not drive it back to the dealer?
First of all, is the idle still rough? Most E34 M5s have a rough idle, something that a grounding kit will usually fix.
Secondly, if your dealer changed the (wheel) shims, the rotor(s) may be rubbing a little on the brake calipers because they were disturbed. Hopefully, he put the correct shims on. Get the car up on a lift and rotate the wheels manually, looking at the brake rotors for any side-to-side movement or rubbing from the calipers.
Depends how rough the idle is, but they don't idle like a normal car because of the cams needed for 90 bhp/litre without variable timing.
You haven't said if the noise occurred on the way home or on start up after you got home and the car had had time to cool. The air pump kicks in after a cold start to burn excess hydro-carbons in the exhaust (again a result of aggressive cams) before the cat lights up. The sound is as you describe, and shuts off after a few minutes. The air pump is on the right front of the engine, and the noise makes you jump when you haven't heard it before.
I suspect that in relation to idle your dealer was referring to valve shims, which will have nothing to do with your brake discs.
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Thanks for all the replies. Turns out it is a noisy clutch. They replaced the tranny fluid with ?ATF? and now it sounds a little rough. Not so sure that is cool with me.
I am pretty far from Newbury, but I can make a trip for the car. Is there anyone in particular I should talk to?
If it's the transmission - you can relax a bit. The easy way to test this is that the noise should go away when the clutch is pushed in.
1. It is "normal" for these transmission to rattle a bit due to loose tolerances on the reverse gear shaft (or something like that) and the relatively rough idle. A little rattling does not indicate imminent failure.
2. The rattle probably used to be there, but thicker fluid in your case was just masking/damping it.
If you don't like the noise, switching to a heavier weight gear oil (such as Redline MT90) may reduce the rattle - though it's really only masking it. It may also change the way the transmission shifts (especially when cold). Each box seems to be a little different when it comes to what oil works best. ATF is relatively low vicosity (around 75W I believe) and is what BMW filled it with at the factory.
Cheers.
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If it's the transmission - you can relax a bit. The easy way to test this is that the noise should go away when the clutch is pushed in.
1. It is "normal" for these transmission to rattle a bit due to loose tolerances on the reverse gear shaft (or something like that) and the relatively rough idle. A little rattling does not indicate imminent failure.
2. The rattle probably used to be there, but thicker fluid in your case was just masking/damping it.
If you don't like the noise, switching to a heavier weight gear oil (such as Redline MT90) may reduce the rattle - though it's really only masking it. It may also change the way the transmission shifts (especially when cold). Each box seems to be a little different when it comes to what oil works best. ATF is relatively low vicosity (around 75W I believe) and is what BMW filled it with at the factory.
Cheers.
1. Yup. It actually becomes prevalent after switching into reverse.
2. I understand how the thicker fluid would mask it, but here is my question: If the lighter fluid causing the clutch ot make noise, which I assume is generated by the vibrations cause some metal on metal shaking, wouldn't the thicker fluid reduce contact and therefore wear?
3.Cool. What do you use in yours?
Linear Mode
