Strange Noise - usually just as setting off

[CaptainCarNose]

Hoping somebody might be able to help - the z3 has started making a strange noise - normally most obvious just as I set off or shortly after setting off.

it comes from the back of the car and almost sounds like when You drive over a can - a hollow metal crunching sound, followed by some other metallic taps. it tends to be when selecting a new gear or shortly after, maybe as the clutch is released, possibly clutch in.

it’s similar to a rattle of loose exhaust component but there its not a constant noise, it doesn’t happen going over potholes or anything. I think I can feel it slightly through the pedals indicating a part of the drive chain but it could just be vibrating from elsewhere.

it sounds horrendous but then it’s difficult but make it repeat it to try work out where it’s coming from!

it had a new cat and exhaust a few months back, I even wondered if maybe it’s bits of the cat or exhaust rattling which are only loose as it’s starts? Seems unlikely but the sounds are like that.

also wondered if it could be the diff as it sounds near the back, felt through drivechain but only bad when the car first starts so maybe something seizing.

could maybe even be brakes related as I sometimes also feel it slowing for lights or pulling away - again in these situations Im using brakes, clutch, gears etc

thanks in advance

 

[Nodzed]

Have a look at the front of the rear silencer, is there a round weight there? If yes is it loose, sliding on its post? Seen this on a few zeds its some sort of device to stop exhaust resonance, and they become loose and can slide forward and back. Chances are you don't have one if the exhaust is a replacement one, and its something else.

 

[Rudyrov]

You have to get the car on a lift and check things out.

 

[CaptainCarNose]

Hi All, going to get it booked in with a garage somebody has recommended on this forum. I took it somewhere near me and they don’t seem to have identified and fixed e source of the noise.

It had also developed a bit of a swish-swish-swish sort of noise which increased with speed and they identified this as corrosion to the “back plates” of the rear brakes. They cleaned them up and that noise has gone but they said they need replacing. He said the whole back end is corroded and there might be trouble removing and replacing bits etc. I had noticed just from looking that bushes etc looked really warn.

ive seen people on here talk about getting the whole rear end refurbished and replaced. What sort of cost / time would I be looking at for this? I’d like it all to feel new and tighter / less knocks and noises etc!

im hoping the new garage that has been recommended and are known for working on classics will be more optimistic / comfortable with the challenge!

Cheers

 

[pgunter]

@Lee Rear end rebuild. Costs involved.

 

[t-tony]

Hi All, going to get it booked in with a garage somebody has recommended on this forum. I took it somewhere near me and they don’t seem to have identified and fixed e source of the noise.

It had also developed a bit of a swish-swish-swish sort of noise which increased with speed and they identified this as corrosion to the “back plates” of the rear brakes. They cleaned them up and that noise has gone but they said they need replacing. He said the whole back end is corroded and there might be trouble removing and replacing bits etc. I had noticed just from looking that bushes etc looked really warn.

ive seen people on here talk about getting the whole rear end refurbished and replaced. What sort of cost / time would I be looking at for this? I’d like it all to feel new and tighter / less knocks and noises etc!

im hoping the new garage that has been recommended and are known for working on classics will be more optimistic / comfortable with the challenge!

Cheers

Where are you located?

Tony.

 

[CaptainCarNose]

Where are you located?

Tony.

Near Leeds, West Yorkshire

 

[MikeK]

Mine has some rust above the rear shock absorbers and is causing a similar noise but z3s have this issue with the weak differential mount so maybe check that too. If its just some loose rear suspension component should be cheap and easy to fix.

 

[CaptainCarNose]

Now taken to two garages, not just said corrosion of back plates which they have adjusted to stop rubbing but there is a definite metalic clunk / scraping noise x think it has to be related to the gearbox or clutch.

both garages said they didn’t hear anything but the second I left it was clunking down the road!

going to try one more garage but then I don’t really know what to do!

 

[CaptainCarNose]

I’m going to order a pair of rear back plates - any recommendations for 3rd party suppliers as I hear bmw are expensive?

are there any other components worth swapping at the same time?

thanks

 

[t-tony]

You have to remove the rear hubs to change the back plates (unless you use the "split" method), and so you will possibly want to fit new rear wheel bearings.

Tony.