'88 240 DL Sedan 123699.3 miles

Bosal exhaust system replacement parts warning.

I have over the last year replaced the entire exhaust system on my 240. First the header pipe and the catalytic converter (Cat). I replaced the Cat due to the flanges between the header pipe and the Cat being rust welded together and I was not interested in the fight so I saved it to disassemble and wear out sometime in the future.

Second everything behind the Cat. The resonator and muffler look to still have some miles on them. But due to me finding pipe leaks and my emission test dead line looming, and while we are still getting snow and rain and below freezing weather, I just pulled and replaced the resonator and muffler to save time and torture. I was only marginally successful on the torture.

First I plugged the tail pipe to check for leaks and there was no pressure. It was obvious the tail pipe had multiple small holes along the seam. So I replaced it.

I plugged the system again and heard and found leaks at every joint except between the header pipe and catalytic converter.

I replaced everything between the Cat and the tail pipe and for whatever reason it only then became obvious that the Cat is short. I went around with the manufacture who is all New Jersey "know the answer." To their credit they set me up with a local parts dealer (the first one I purchased via Importec). To their discredit the second part was also short. The first one was 34 3/4" the next one is 35 1/4" and neither of them the stated +/- 1/8" of original 35 3/4". The entire exhaust system was pulled forward to try and get a connection. There was not enough overlap to get an air seal and the tension pulled the connection apart (this may have been due to the clamps - see below). I finally found, an unfortunately thin walled, pipe extension cut an inch off the Cat and installed it with Permatex Muffler & Tailpipe Sealer and a clamp.

Do take care that the clamps sold via internet were spec'ed too large (52-55mm inlet, 55-58mm outlet) and I needed to purchase smaller clamps locally for 2 1/8" (-). 51 mm = 2.125 inches. I did not go back to find why the outlet end was so tight but my guess is that it needs to be 54 mm (-) or 2.25". These were circumferential clamps as I was having difficulty getting seals with the guillotine clamps. There was no slack in the first set of circumferential clamps to tighten them after they came down around the pipe. They just jamb at the ends. I suggest getting the circumferential clamps instead of the 'U'-bolt or guillotine clamps.

I dropped the header pipe and found the plate at the exhaust manifold was not flat and there was a small particle of weld debris on the surface at the center of the leak. I filed the plate flat and reinstalled the header pipe to the exhaust manifold with Permatex Ultra Copper High Temp Silicon (101BR) on both sides. Let it sit 30 hours. The silicone blew out after 20 miles +/-.

I strongly suspect the leak at the exhaust manifold to be the mystery gas mileage eater I have been looking for and glad I found it prior to the emissions test. It also may have been contributing to very subtle vibrations I was picking up in the wheel and pedals as well as the rear view mirror. I originally found the spark plug caps were unwinding (?) and causing vibration and after the header pipe repair it disappeared all together. Maybe the header pipe was causing some vibration that was unwinding the spark plug caps (?) - no telling.

As I now have installed the header pipe two times I put Permatex Anti Seize on the bolts and as long as I had the stuff I applied it to the end of the Cat to help that assembly slide into the resonator and - God save me - future disassembly.

The axle pipe and tail pipe both needed to be hammered into the muffler due to too tight a sleeve. I will probably need to cut the tail pipe off to drop the system in the future since the pipes are so close to the side walls.

The 240 ran much more smoothly and not too surprisingly quieter. The silicone blew out of the header pipe gasket after 20 miles.

I have no affiliation with Permatex. The local parts store just carries a wide selection of their products. I do wish they would put some effort into distinguishing between the multitude of sealers they sell. It is a nuisance to look through the small print on some 20 tubes of the stuff to see which one applies to a given use. Specifically the temperature ratings for "high temp."

There would seem to be some money here for an enterprising lawyer to take Bosal to task for repeated substandard "manufacturer spec parts." If I ever buy another Bosal part it will be too soon.