Hey guys,

I have an '87 745 GLE AW70L with 290k miles.

The weld on the heat shield for the turndown pipe was busted which rattled like crazy and annoyed me to death. I had to replace the catalytic converter (to pass California's insane smog test) so I thought I would replace the turndown pipe also.

It was difficult to locate an intact turndown pipe as the boneyards pinch off the cats (against federal law to sell used cats) and aren't too picky as to what they pinch off. I finally located one and started to pull it.

I picked up the turndown pipe from the boneyard during a half-price sale. Exhaust pipes are cheap and it only cost me US$7. :D It was a real PAIN to take off though. The three bolts (15mm)that attach the turndown pipe to the bottom of the exhaust manifold were tough to get to. Fortunately I took some penetrating oil, a breaker bar, and lots of extensions. Even so I had to remove the exhaust manifold on the boneyard car to get to the bolts. There was also 3 bolts that clamp on the turndown pipe hanger. These are 12mm and were kind of hard to reach but I managed.

I took the exhaust heat shield while I was at it. It was the newer two-piece version and is a nice replacement of the one piece on my '87. The bolt pattern is the same so they are interchangable.

It was easier for me to remove the exhaust manifold to install the turndown pipe, so I picked up some new exhaust manifold gaskets at Autozone (US$14). Instead of getting new bolts for the exhaust manifold, I picked up a tap and die (8mmx1.25) and all of the bolts went in sweet (after I cleaned them up with the tap and die). I didn't use any anti-sieze or any permatex seal.

I found the catalytic converter online for US$100(including shipping).
http://www.ecatalyticconverter.com/
I had to pick up some three 1/2" bolts/nuts/washers for installing the turndown pipe to the cat. No antisieze there either. The cat came with a ferule and a u-bolt for the tail pipe.

When I test drove my brick I heard a rattling sound from my cat. Oh great... It turned out to be the hex plug in the top was loose. Just remember to tighten that up before you go if you don't have a sensor that fits in there ('87 didn't have a cat sensor).

The trickiest part of the job was getting the exhaust manifold back on. I had to lightly jack up the turndown pipe in order to get my manifold bolts to line up properly.

While I was doing this job, I went ahead and checked the rubber exhaust hangers. I had one that was broken and replaced it with a spare I had.

:D