E36 loud knocking noise. Ideas?

[RobM77]

Over the last few months my 1998 E36 328i sport coupe has developed a loud knocking noise. It's intermittent, and I've yet to get the car to the garage during a period when the cars doing it. You can hear it at very low speed (under 10mph). I've coasted in neutral and even briefly with the engine off and it still does it. I'm not sure where it's coming from, but it sounds like the passenger side of the car. I've absolutely no idea what it is, and no-one I've shown the car too does either. I rely on the car quite a lot so I don't want something major to break all of a sudden!

Any ideas?!

[Mingo]

How is the car handling? Does the back end feel loose? If so, then it might be your rear trailing arm front bush, or a rear shock mount.

Other possibilities could be worn anti roll bar drop links, or if it's more of a clinking noise then it could be a broken rear spring.

[RobM77]

Mingo said:

How is the car handling? Does the back end feel loose? If so, then it might be your rear trailing arm front bush, or a rear shock mount.

Other possibilities could be worn anti roll bar drop links, or if it's more of a clinking noise then it could be a broken rear spring.

Thanks for your reply. I had the suspension completely re-done recently with new bushes, springs and dampers all round. The handling and steering are both absolutely spot on. I changed the front ARB drop mounts yesterday, as they were a bit worn. Still doing it though!

It's a really definite knock - like someone tapping with a hammer on the floor

Edited by RobM77 on Saturday 11th April 15:20

[Mingo]

Have you looked at the guibo that connects the gearbox to the propshaft? It's a rubber donut that can develop cracks over time/hard use and could cause the prop to just about hit the tranmission tunnel or a heatshield.

[gmarks1]

Have you checked that all of the exhaust mounting brackets are secure?

[road_rager]

wheel bearing/s?

[phelix]

When it happens is it rhythmic or random? Does accelerating or using engine braking make it change?

Edited by phelix on Saturday 11th April 20:37

[RobM77]

Thanks for all your suggestions, they're really helpful. The noise isn't rhythmic or linked to speed; it's just a loud knocking. It does it with the engine off too. I think Mingo's suggestion of that rubber mounting may be the most likely candidate. I've checked the exhaust already (as that's exactly what it sounds like), but that's very secure.

I'll let you know what it is when I've got time to look again

[dan101smith]

Brake pads?

[RobM77]

dan101smith said:

Brake pads?

The knock doesn't change if you drive with calipers open, closed up to the disc or biting. Also, the frequency of the knock is random and doesn't increase with speed.

[andye30m3]

Have you checked the rear shock turrets, it's not uncommon for them to brake, more so if you've recently put up rated dampers on.

Easy to check by lifting the boot carpet.

Edited by andye30m3 on Sunday 12th April 23:06

[Doctor Bone]

Donut!

[Clammy]

andye30m3 said:

Have you checked the rear shock turrets, it's not uncommon for them to brake, more so if you've recently put up rated dampers on.

Edited by andye30m3 on Sunday 12th April 23:06

Which is why a lot of people fit reinforcement plates from the Z3 to e36 models.

http://home.comcast.net/~matthew.c.smith/mods/rear...