540 Cats

[compmore]

11/94 aussie 540

I'm getting a bad rattle from one of the cats.Took it to two exaust places today and first said they can fit 2 aftermarket cats and a new flow thru muffler for A$1,000.

2nd place is owned by a guy who has a 99 3 series and they say most aftermarket cats will cause big problems with the computer.They advising me to only fit a euro type which will cost A$2,100 for the cats and fitting.

Could live with $1000 but if you think I need the 2nd option it's probably time to trade it as I have a few other issues to fix on the car which will cost another $1,500

Appreciate any advice you can give us

Geoff

[Roderick]

Shop around to different shops, you can get them for around $500-$600 installed. It all depend on your location.

[compmore]

I'm not so worried about the price can live with the $1000 just don't want to get into any possible dramas with the computer.thats my main concern

geoff

[632 Regal]

shop around for a used one and bolt it up and be done.. of course shake it to make sure it doesn't rattle first. These things usually last a very long time and you could most likely pick up something used for a hundred bux.

[h2oyo]

[QUOTE=compmore;329373]11/94 aussie 540

I'm getting a bad rattle from one of the cats.Took it to two exaust places today and first said they can fit 2 aftermarket cats and a new flow thru muffler for A$1,000.

2nd place is owned by a guy who has a 99 3 series and they say most aftermarket cats will cause big problems with the computer.They advising me to only fit a euro type which will cost A$2,100 for the cats and fitting.

Could live with $1000 but if you think I need the 2nd option it's probably time to trade it as I have a few other issues to fix on the car which will cost another $1,500

Appreciate any advice you can give us

I dont know about euro cars but I know I have replaced the cats on my 95 540i with an aftermarket type and have had no issue with anything because of the cats. For me it was more what caused the cats to go bad, injector, O2 sensor what? I do know that if you dont find what caused them to go bad before you replace them chances are you will be replacing them again as I did lol

[BigKriss]

Is the 02 sensor before or after the cats? if it is after, then in it dosen't matter what cats are there or any.

http://www.realoem.com/bmw/showparts...22&hg=18&fg=05 - I couldn't tell from the diagram , if there cats or mufflers.

[compmore]

Thanks guys.Good advice although you have me thinking now as to why it's failed.Your the second to say there must be a reason.The o2 sensors are fairly new and the only issue i can think of that may have caused it was a brief overheating when the aux coolant pump died a few months back.

the sensors are between the block and the cats so was thinking if they sending signal before the cats then hopefully be ok.

the diagram would be the cats as its cats,resonators then muffler at the back.

i'll probably go the aftermarket ones for $1,000 and cross the fingers

geoff

[genphreak]

Thanks guys.Good advice although you have me thinking now as to why it's failed.Your the second to say there must be a reason.The o2 sensors are fairly new and the only issue i can think of that may have caused it was a brief overheating when the aux coolant pump died a few months back.

the sensors are between the block and the cats so was thinking if they sending signal before the cats then hopefully be ok.

the diagram would be the cats as its cats,resonators then muffler at the back.

i'll probably go the aftermarket ones for $1,000 and cross the fingers

geoff

Cats can fail from poor running and/or coolant getting into the exhaust - particulalry if someone has replaced (or partically blown) a headgasket. Be 100% about your engine's operation and history before fitting new cats, they may just fail again...

My 2c is to:
- As Jeff said; go second hand as OEM is best (the reason one buys a Bimmer is that everything is built to an optimum spec in the first place, if something critical like exhaust isn't it wouldn't be a BMW).
- Be sure to test and/or replace the O2 sensors, they are critical to good running and may be faulty.
- Exhaust shops are not experts oon engine performance and tuning- their advice will often lead to poor economy and even worse performance
- OE and dropin parts can be crapper than you think (obviously not always, but more often than you think) ... OEM is usually better.

Best of luck!@

[Pang]

Geoff
I'm in Australia and had the same problem and similar quotes with my 530.
Although illegal I removed the cats and had two pieces of stainless steel exhaust pipe welded in.I have had no problems at all.No error messagers diplayed,fumes can be a bit stronger when first started.

[Bill R.]

One shop is handing you a line... On an obd1 car like yours you should only have a 02 sensor before the cats unless you have a japan market model which has a cat temp sensor in the back of the cat.
Either way the aftermarket cat won't affect the computer on your car. The aftermarket cats here in the US work fine, with the exception that they don't last as long as the original and don't stay heated up as long since they have less material. I've put a number of them on with no problems since they cost about 10% of OE they are easily the most installed around here. Later models in the US have obdII which has a sensor before and after the cat which makes the cat a little more critical.