what is causing my rumble?

[m3pat2]

If all the spark plugs look consistent then it's not a leak at the header.

The leaking header will run leaner than the other cylinders.

Also check to see if the muffler has blown out/or leaks.

Mine blew out from the front side of the muffler, not the back as I had assumed. So check the side where the center section connects to the muffler, the welds broke on mine where the pipes were welded to the muffler.

[petro]

if the engine is running ok but there is a lot of noise "rumbling". Almost sounds like there could be a hole somewhere in the exhaust line like other posters have mentioned.

you could look down the line of the exhaust system, may as well check the bolts while you are there like connection of exhaust to header and the bracket that supports exhaust there.

The only thing is that if there is a crack or hole in the header area it might be hard to see. And also if it is on teh top of the exhaust or muffler you might not see unless it is off the car.

There must be some sort of tester to detect exhaust leaks.

[hardtailer]

stuff an old rag in the tail pipes and listen for a hissing sound. That's where your leak is.

[sirrus]

sounds...

Guys,

Sorry to drag this back up again. I've been out of town for a couple of weeks but when I got back I briefly had time to record some sounds of the 'issue'.

I also checked for exhaust leaks by ear w/o much luck and I loosened/checked/re-tightened the alternator belt to make sure it wasn't causing the problem. (Only aux left is water pump and power steering but I doubt they could cause something like this).

Here are the sounds.

1) S14, in the engine bay: http://68.178.134.199/sounds/m3/s14_tick.mp3

2) Exhaust sound:
http://68.178.134.199/sounds/m3/exhaust_tick.mp3

Thanks for any insight...

:sosad:

[Ash]

Your exhaust sounds like a WWII aircraft
:1:

[oscarcab0]

Take that M in to an exhaust specialist, have them put it up on a hoist and sort out where that exhaust system is stuffed.

(sorry for the edit.....I hate typos)

[petro]

it does sound like it is being blocked somehow. could a poor little critter have crawled into the exhaust while it was stored? that would match up to your circumstances... or cats falling apart?

[sirrus]

Originally posted by petro
it does sound like it is being blocked somehow. could a poor little critter have crawled into the exhaust while it was stored? that would match up to your circumstances... or cats falling apart?

Actually, before the recent maintenance stuff, the most recent service job was a cat replacement (7-8 months ago) w/no problems.

I suppose it's possible that something climbed into the exhaust, but it would have to have been an ambitious little bugger since I have the supersprint DTM pipes.

[oscarcab0]

Oh hell, I can't resist.........maybe you have a snake up your exhaust.......that whole situation is weird. I stand by what I said earlier.......get that thing up on a hoist and get it checked....from head to tailpipe. WEIRD....

[t13vom]

...Sounds Interesting...

After having pulled a nested mouse family out of a 7-series blower motor anything is possible.

The ticking sounds like lifters...

If you had the facilities I would say disconnect the exhaust and fire her up. Maybe a baffle has collapsed some were if a varmint is not the problem...

Either way good luck!

Cheers!

[Verruckt]

Any update on this? was there a fix?

I've got the same EXACT issue with my m3.

And it also sat for about the same time, a good 4 months without being run.

[sirrus]

Originally posted by Verruckt
Any update on this? was there a fix?

I've got the same EXACT issue with my m3.

And it also sat for about the same time, a good 4 months without being run.

Unfortunately, no. I have been swamped with things non-M3 related for months and am in the process of replacing the water pump to see if somehow the ancilliary components are causing the issue.

It has killed me this summer not being able to drive the M :(.

I'll let you know of any updates and please do the same if you have any luck.

[Verruckt]

Actually, I do have an update. I also find it pretty interesting that my car sounded the same as yours.

It turned out that my valves were shimmed too tight in cyl #4 (couldnt even fit a .1 feeler gauge in there) and the valves were open all the time causing incomplete combustion. It also was causing a mean ticking.

Compression on that one cylinder was at an unreadable amount, pretty much 0 PSI, and this was just another hint.

I re-adjusted the valves properly and it runs great now.

I noticed you mentioned that you stored it for winter, and did a valve adjustment and now it runs like you say it does, maybe you too have adjust them too tight? It's worth a shot.

[sirrus]

Originally posted by Verruckt
Actually, I do have an update. I also find it pretty interesting that my car sounded the same as yours.

It turned out that my valves were shimmed too tight in cyl #4 (couldnt even fit a .1 feeler gauge in there) and the valves were open all the time causing incomplete combustion. It also was causing a mean ticking.

Compression on that one cylinder was at an unreadable amount, pretty much 0 PSI, and this was just another hint.

I re-adjusted the valves properly and it runs great now.

I noticed you mentioned that you stored it for winter, and did a valve adjustment and now it runs like you say it does, maybe you too have adjust them too tight? It's worth a shot.

Valve clearances were the first thing I checked (and double....quadruple checked ). My compression numbers were good, too.

I may try loosening up the clearances a bit and see if maybe somehow that is the problem, but I only had to replace 1 shim and swap 2 others.

Thanks for the feedback.

[D.R.]

Sounds like the motor is fine, take off the muffler (it's only two band clamps) and see if that helps.