1990 535i Exhaust System

[Lane]

My '90 535i has exhaust problems (106,000 original miles). There's a shudder in the exhaust system when accelerating from a stop that keeps getting worse. Now it's making a rattling sound when I decelerate and the exhaust system seems to be clogged up because it's starting to hiss/whistle after the engine has warmed up. I realize this can be very dangerous and am tempted replace the entire exhaust system, but am confused as to how many parts there are. There is a front, center and rear muffler, as well as a catalytic converter? Would it be wise to replace everything? Is there any where you might recommend where I can order the entire system and related parts? to Any suggestions? Input is greatly appreciated. Thanks.

[Kalevera]

Lane, the exhaust consists of a downpipe & catalytic converter, a resonator and a rear box. The first two are an integral unit, as are the last two (from the factory, at least).

If the cat is clogged, put a vacuum gauge on the engine and rev it. Vacuum should fall to 0 from anything between 15-22 at idle.

There are plenty of sources for used exhaust systems, but I don't recommend any of them. A new one is your best bet; the logic here is that the one currently on the car probably lasted 15 years, and a new OEM will give excellent performance for an equal amount of time (probably longer than you'll have the car).

The rattling could be from a rusted heat shield, or -- more likely -- a bad rubber doughnut or figure 8.

best, whit

[Lane]

Thanks, Whit. I'm checking on finding a new exhaust system.

[callen]

Replaced entire system in my 91 535. Was relatively easy and inexpensive and all direct replacement. Purchased cat from Autozone so check with them as well as call Patrick at BMA (they have good source for aftermarket Cats). I purchased other two peices, muffler and resonator from Beckers import. Got misc. hangers and gaskets from dealer. That was 3 years ago and no problems...and as added bonus system weighed half that of OE.

[Jay 535i]

I just installed a new exhaust last week.

Hopefully your cat is fine. It's expensive, and there's no benefit to replacing it if it is okay, which it probably is.

I had to replace everything aft of the cat. I went for something that wasn't OE, but meant to be interchangeable with the OE. CDN$1000 for parts, $200 for labour.

Great results. Still feeling the pocket pain.

[Lane]

Thanks, Callen. Much appreciated!

[Lane]

Hi Jaylebo...Thanks for the response. I'm sure my cat is toast because I can feel so much heat coming from under the car after being out for a drive and the sound coming from it (pressurized whistling) makes me frightful that it's clogged. Being in California with stricter emissions laws than most places, I opted to replace the whole system. Better safe and new than sorry down the road. I paid just under US$1,000.00 for the parts. Thanks much!

[Jay 535i]

Hi Jaylebo...Thanks for the response. I'm sure my cat is toast because I can feel so much heat coming from under the car after being out for a drive and the sound coming from it (pressurized whistling) makes me frightful that it's clogged. Being in California with stricter emissions laws than most places, I opted to replace the whole system. Better safe and new than sorry down the road. I paid just under US$1,000.00 for the parts. Thanks much!

That sounds about right.

I agree there's a certain satisfaction that comes from knowing such-and-such is new and will last for years. Cutting corners doesn't pay off in the long run.