Help diagnoese my E46 M3 problem - Knocking noise at rear!
Discussion
Hi all,
Hoping someone can help diagnose this problem. Car is a 53 plate E46 M3 with 105K miles. I have just returned from work and a knocking sound has started emanating from (I think) the back of the car, it's hard to tell exactly as it only happens when moving! It seems speed dependent (i.e. knocking is slower at lower speeds and does not appear to be gear dependent), it only seems to happen in gear and under engine load (i.e. not constantly) and strangely seems worse under low engine load than high (not that I have been giving it any beans since it started). It seems to tail off and disappear above about 40mph. No warning lights and other than the noise it does not seem in any way off.
The car has had the rear diff seals, bushes, rear springs replaced though not that recently that the work is the cause (just to rule out the usual rear spring knocking noise that I am aware off).
I have had a look underneath and there is no obvious loose bits but have not had it up on a ramp.
My initial thoughts are diff related, and I suspect an expensive trip to the garage is looming! I may stick a bit of card under the diff and check for oil leaks.
Anyone had a similar issue? Any help is greatly appreciated,
Jim
edited to change smiley face to the sad face I meant!
Hoping someone can help diagnose this problem. Car is a 53 plate E46 M3 with 105K miles. I have just returned from work and a knocking sound has started emanating from (I think) the back of the car, it's hard to tell exactly as it only happens when moving! It seems speed dependent (i.e. knocking is slower at lower speeds and does not appear to be gear dependent), it only seems to happen in gear and under engine load (i.e. not constantly) and strangely seems worse under low engine load than high (not that I have been giving it any beans since it started). It seems to tail off and disappear above about 40mph. No warning lights and other than the noise it does not seem in any way off.
The car has had the rear diff seals, bushes, rear springs replaced though not that recently that the work is the cause (just to rule out the usual rear spring knocking noise that I am aware off).
I have had a look underneath and there is no obvious loose bits but have not had it up on a ramp.
My initial thoughts are diff related, and I suspect an expensive trip to the garage is looming! I may stick a bit of card under the diff and check for oil leaks.
Anyone had a similar issue? Any help is greatly appreciated,
Jim
edited to change smiley face to the sad face I meant!
Edited by JimboM3 on Tuesday 14th December 19:41
Trouble is with something like that car, so much of the important stuff is around where the noise appears to be!! for what my opinion is worth, I would swallow a little bit of outlay now by taking it to a professional to diagnose the issue before it potentially moves into something more problematic!
(Sorry if this doesn't help!!)
(Sorry if this doesn't help!!)
Get it to an independent specialist and ask them to check it underneath paying specific attention for any crack in the subframe. More and more E46's are suffering with this now as they get older.
It may not be this, but its likely to be the most expensive thing that could be wrong.
The good news is BMW will sort the problem FOC if its under 10 years old and unmodified.
It may not be this, but its likely to be the most expensive thing that could be wrong.
The good news is BMW will sort the problem FOC if its under 10 years old and unmodified.
Thanks for the replies everyone. I am now strongly suspecting the diff (or something connected to it). I had a good look round in daylight and I can't see anything obvious (loose trim etc) and there are no oil leaks that I can see. Just confused why the noise would be intermittent if it was the diff? I can't remember what type of diff the M3 has, does anyone know any common problems with it (more out of interest than anything)? I will be googling later when I have time.
Also, has anyone had an indy swap a diff before (or I guess rebuild) to give me an idea of cost? I will be booking into a garage ASAP. Typically not a great time for it to happen!
I have heard of subframe issues, but not seen any pics or detailed description on PH before. Does anyone know what the problem is / what fails? Hopefully just for future reference!
Thanks again,
Jim
Also, has anyone had an indy swap a diff before (or I guess rebuild) to give me an idea of cost? I will be booking into a garage ASAP. Typically not a great time for it to happen!
I have heard of subframe issues, but not seen any pics or detailed description on PH before. Does anyone know what the problem is / what fails? Hopefully just for future reference!
Thanks again,
Jim
JimboM3 said:
I have heard of subframe issues, but not seen any pics or detailed description on PH before. Does anyone know what the problem is / what fails? Hopefully just for future reference!
Thanks again,
Jim
Its not actually the subframe itself, but the floor pan near the subframe mounting points - it cracks because the floor is so thin.Thanks again,
Jim
Have a look here at a nasty example... http://video.google.com/videoplay?docid=8362789948...
If it is a subframe tear, BMW will almost certainly repair it under goodwill as the car is less than 10yrs old. This seems to happen a lot to e46 M3s, but BMW have been extremely good at holding their hands up when the issue appears.
Is the car modified in any way? If so I would revert it back to stock.
Is the car modified in any way? If so I would revert it back to stock.
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