Exhaust System

This section contains special information on the rear suspension that supplements the Service or the Bentley manuals.

All information contained in this FAQ is provided by BMW enthusiasts who are not typically fully trained in the art of BMW maintenance. As such, all information in this FAQ is provided "as-is". Any use of this information is strictly the responsibility of the using party. The supplier of the information and the Webmeister assume no liability for incorrect information or use of this information.


Exhaust Assembly Replacement Tips


Exhaust Assembly Replacement Tips - "Gene M." <mclan@worldnet.att.net

I just replaced the exhaust (middle and rear muffler assembly) on my 86 635 with a Boysen OE unit. I have done exhaust replacments on E23, E24 and E28 before and it's always been difficult getting to the nuts and bolts that connect the exhaust assembly to the catalytic converter, especially getting at the top 2 bolts and nuts. I was able to get it replaced on the 635 without extra frustration this time using the following.

First, even though these are 13mm bolts and nuts, there is play in the 13mm wrench and sockets so use a 1/2" wrench and a 1/2" socket (3/8 inch drive). When I dropped the exhaust on my L6, I rounded some of these nuts and bolts using the 13mm stuff. There will virtually no play with the 1/2" wrench and socket.

I jack up both wheels at the same time on the passenger side of the car using Norm G's technique and put 4x12's (or old TRX rims) under the tires instead of jack stands for max. stability and clearance in the work area. One side up seems to work fine.

With a floor jack under the muffler at the back of the middle muffler with the handle coming out between the passenger side wheels, jack up the muffler a little and take off the hangers (2 middle and the large rear--I unbolt the holder instead of struggling to get the black Krispy Kream.off). Slowly drop the muffler down with the jack as far as possible.

Spray all 6 of the nuts and bolts with Rost Off, PB Blaster or equivalent and let it soak for awhile. On the top 2 top nuts and bolts, use the 1/2" box wrench on the nut on the back. On the bolt, use the 1/2" socket with a 3/8' drive 3 inch wobbly, then a 12 inch wobbly, then a ratchet or hinge handle (longer handle the better because these can be on tight. I have tried before using a u-joint
but when trying to torque bolts loose, the u-joint seems to flop around and take away a lot of the torque to the bolt. Other combinations of wobblies don't seem to keep the socket flush on the bolt whe torque is applied. On the 4 lower nuts and bolts, a hinge handle 3/8" drive with just the socket should get these 4 off.

Have new nuts and bolts, the one triagular gasket, new hangers at least for the 2 middle--the Krispy Kreme maybe too, and some anti-seize on hand for the installation. Positioning the jack and its handle in the same location that was used to lower the old one will allow precise one-leg over the handle jacking while rotating the muffler to line up the bolt holes.

Remember to put on some glasses when under the car doing this. A lot of grit falls down.