Catalytic Converter Question

[pedroguard]

I have an interesting problem. The valve in the right exhaust pipe has been staying closed for several months. I know the valve is there to assist in warming the cats while the system is cold. I overrode this by unplugging the solenoid that controls the valve. (It's in the trunk under the floor. Long search, ended with much profanity.) I had let it run with the valve shut for a while and didn't think too much of it. Obviously it isn't the solenoid. I figure that the comp was holding it closed to try and get the cats to do their thing.

The only code I get is a P0442 which is a small vacuum leak (I think). I changed all of the vacuum hoses a few weeks ago and did the valve cover gaskets yesterday.

I had believed that the cat section of the exhaust was leaking pre the cats (can hear it, especially when the smog pump is running) but last night I found that the leak was in the rear header bank. I had intended to pull the headers anyway since I didn't know for sure where the leak was. There is a crack in the pipe that goes 3/4 around it. I will have that welded up tomorrow. I know that the catalytic converter couldn't have been running at peak efficiency, especially with the size of this leak. It has been leaking for months but I didn't decide to fix it until now.

I have already purchased an aftermarket cat system from Bavarian Autosport and am now wondering if I should put the old system back on or go ahead with the new one. I also do not know yet if Bav Auto will take the new one back if I decide to go with the old. The old one is about twice as heavy as the new and has the resonator cans that the new doesn't have. The heat shields on the old one rattle, but that is nothing that some safety wire can't fix.

The car is a 96 328is with 141K miles on it. Should I use the old or new cats? What about this back pressure valve issue?

 

[chief]

I just replaced the cats on my 96 328i. I got it from BavAuto also. There were 2 minor problems with the replacement cats i received. 1st. the left pipe was too short and required some custom work to join the pipe to the muffler pipe. 2nd. the O2 sensor hole on the left pipe is vertical to the top. This can cause problems with the wiring. In fact i am awaiting an O2 sensor to replace the after cat sensor on the left pipe. My plan is to create a 3/8 inch dome above the O2 sensor to prevent chaffing of the wires.

 

[pedroguard]

I already put the original back on. Just fixing the crack made a world of difference. More power, less noise. I think I killed one of the O2 sensors with the Bav Auto pipe set. It was going to require no fewer than three bends to make the thing fit, it was pressing the O2's into the heat shield badly and was completely supporting itself from the headers. The rear mounts might as well not been there. Mine killed the left sensor also.

I'm tired of fixing that car anyway. I think I'll get rid or it now. During my incarceration under the car I couldn't help but notice all of the suspension rubber bushings are worn out. I wish I had enough funds to allow me to take it to the machine gun shoot and blow it up. www.oklahomafullauto.com

 

[chief]

I replaced all of my rubber hangers while i had the car on the hoist. With a 10 year old car that has 132000 on it i did not think that was out of the question to replace them.
Will be under the car in the next couple of days, Friday most likely to replace the O2 sensor.