Knocking from behind driver (RHD) at low revs.

C

chris53z4

Member
Hello,
I'm new to the forum. I have a 2004 z4 2.5. It has 40000miles on the clock. At low revs around 1200 rpm in any gear or neutral there is a knocking noise from behind the right-hand seat. It sounds like a fuel pump to me. It is intermittent and seems to be worse when there is less than half a tank of fuel in the car. Over 1200 rpm it seems to disappear. I haven't noticed any issues with a lack of power/miss fire etc.

I have hear that z4's are notorious for problems with the low pressure pump but have read that this is usually a whining noise.

If anyone could help me out I would appreciate it. Thanks in advance. Chris.
 
I had a knocking around the same area, traced it to the space beside the battery, the tool kit was rolling around in there, tucked a rag in beside it.
I hope your problem is that simple. :driving:
 
bat1959 said:
I had a knocking around the same area, traced it to the space beside the battery, the tool kit was rolling around in there, tucked a rag in beside it.
I hope your problem is that simple. :driving:
Click to expand...

That was one of my first thoughts as well.

It will do it when stationary and must be mechanical as the knocking is at a constant speed with the revs and remains at the same pitch, volume etc. Its a dull but sharp tapping noise if that makes sense.

Thanks for your input and time though. :)
 
Z4 Beemer said:
Is it when the car is moving, or stationary?
Click to expand...

Hello. Both situations. It will quite happily knock away in neutral with the handbrake on if I put the revs to around 1200.

Thanks.
 
I have a similar sounding issue on my E89 and I mentioned it to the dealers when it was in for servicing. I think on mine its when the fuel level is between one quarter and three quarters full. Its a sort of faint knocking/tapping noise. They explained it was a fuel return flap, and nothing to worry about! Its basically fuel getting returned to the tank via a flap that can sometimes be heard, pretty much over your right shoulder.
 
Z4 Beemer said:
I have a similar sounding issue on my E89 and I mentioned it to the dealers when it was in for servicing. I think on mine its when the fuel level is between one quarter and three quarters full. Its a sort of faint knocking/tapping noise. They explained it was a fuel return flap, and nothing to worry about! Its basically fuel getting returned to the tank via a flap that can sometimes be heard, pretty much over your right shoulder.
Click to expand...

Good news!! That sounds feasible, pretty poor for an expensive car though. Thanks for your input, I really appreciate it. :thumbsup:
 
You must log in or register to reply here.
Back
Top Bottom