The exhaust manifold to muffler are studs from the factory. The likelihood of snapping them off when you try to remove them is pretty high. Heat & Penetrating oil are your friends. When you snap them, they are replaced with Inconel bolts from BMW. They are a bit pricey.

You can get to the driveshaft without unbolting these if you can unbolt & detach the remainder of the exhaust system, it will hang down enough to get to the Guibo.

I wrote a posting on noise earlier and this sounds familiar. I replaced the Front Driveshaft (U joint seized) Replaced the rear springs (pig tails broken), I had just replaced the Guibo as the bearing was failing. It turns out the root cause of the noise was none of the above. It was the subframe bolts needing retorquing.

 

Hi,

Thanks for the reply. I figured they were pressed in studs and probably a nightmare to get out if you shear the bolts off. I did look up the bolts you were talking about on realoem and you're right... They're listed at 24 bucks a piece! I was thinking about letting the exhaust hang down but I'm concerned about putting stress on the cat/manifolds I'd hate to crack one of those suckers. Did you do this yourself or have you seen this done? It sure would make life a lot easier if I could just lower it out of the way a little bit.

I'm pretty sure my noise is somewhere in the drive line. It's not really loud, more like a rattling noise. It sounds similar to an engine knocking from low octane or bad fuel. It's intermittent and only does it under light acceleration. It goes away when I lift and when I accelerate hard. Very similar to when the front shaft went.

Where are the sub-frame bolts you mentioned?

 

I did do it myself on both my x3 and e39. Both have the M54 engine. I did support the muffler with my floor jack so it didn't just hang and lowered it in a controlled manner.

That does sound like the Center Support Bearing. I have replaced that as well. Since you have to drop the driveshaft, it is a good time to replace the Guibo. As I recall, I removed the rear transmission mount & supported the transmission as well. You can actually buy a replacement bearing for the Center Support Bearing and save a few bucks. I just replaced the whole thing. It's not particularly hard, just a little cumbersome without removing the exhaust.

There are 6 chassis bolts 2 in the front pretty much in line with the shocks and 4 in the back of the subframe right behind the wheel wells. You have to pull back some of the plastic cover to get to 2 of them. On the front ones, don't get the one's that hold the rack on confused. They are all external torx.

 

Awesome.... that's great to hear and that's exactly what I'm going to do. I figured removing those exhaust nuts could be an absolute nightmare. It's good to hear that you've done it without any issues. I'll do an inspection first to see what I need to buy then do it all at once. If I'm going to rip everything out I will replace the Guibo and the whole center support hanger and bearing. Maybe I'll get lucky and the shaft U-joints won't be shot and I won't have to replace the whole shaft.....but I'm not holding my breath! I'll definitely check the sub frame bolts when I'm under there...

Thanks again... You helped a LOT!

 

Of course it is going to be whatever its going to be, but center support bearings seem to fail far more often than the U joints on rear driveshafts.

 

bolt tech

with very corroded high risk/high cost to replace fasteners we always use the nut splitter to remove them in the blink of an eye ....or .....you can peanut grind down one side till just caressing the OD of the stud thread and then they wind off much easier

 

So I had my car up in the air last night to evaluate the process of lowering down the exhaust and pulling the heat shielding off so that I could inspect the rear drive shaft, support bearing and Guibo. I quickly realized I would need more time than I had last night. However, while I was under the car I started poking around up near where the exhaust bolts onto the headers/cats. I grabbed onto the rubber vibration dampener that's mounted on the exhaust pipe and found that it was really loose...I mean sloppy loose AND I could rattle it around inside of the mount. The sound it made while I was doing that was pretty damn close to what I've been hearing so I decided to try and tighten it up.....NO Go. It was as tight as you could crank it in.

So, instead, I removed it completely, dropped the car and took it for a ride.... Problem solved! The intermittent noise I'd been hearing was the vibration dampener rattling around in the mounting cup....unbelievable. This exhaust must vibrate pretty significantly to have to have a dampener designed in...(there's another one on the rear end of the exhaust as well). I did a little checking on line and couldn't find a replacement so it's just going to stay off for now.

 

where to get one

good sleuthing !...also ....a pal got a hanger/damper kit from the bavauto

 

kits

some stuff in this link
http://www.bavauto.com/se1.asp?dept_id=65

 

Thanks... I got lucky for once! I'll check out what Bavauto has to offer. For now I'm digging the silence!