Catalytic Converter Questions

[stimmy]

(I apologize for the repost from Newbie, but I've yet to get any sort of definitive answer)

I'm new to the BMW community but anxious to dive in. I'm posting this message in two forums as I'm ignorant to both of their capabilities and prescence. I apologize for any annoyance I've caused with this, but I'd like to find a home, and the only way to do so is by correspondance, eh?

So, I just bought my first beamer. I had a Mercedes before ('84 300D) and fell in love with German manufacturing, but I did not realize the extent until I drove this car. It's a 1992 318iS that has been very very nicely maintained. There are a few minor imperfections, but they are mostly cosmetic. When I bought the car, I was warned that the catalytic converter was rusted, but hadn't yet show signs of malfunction. A few weeks later they started to.

A slight rattle at first turned into my baby sounding like it was Japanese and it's only gotten louder. So, it's about time to make a move. I checked out the heat shields, and one of them does need to be replaced, but the noise was coming straight from the cat. Now my question is multi-part:

a) What has my delay in fixing the cat done for harm to my car? Could it have hurt the oxygen sensor used for monitoring (the second one), and how do I test this?

b) Where can I locate heat shields at a decent price? Is Bavarian my best bet?


c) What should I look at for Catalytic Converts? I basically have four choices here, as far as I know, due to the fact that I definitely don't have the money for a stock one ($1,000 from Bavarian).

1. Aftermarket direct fit cat like http://www.all-catalytic-converters...-converter.html which would run me about $250 or bavauto which would cost me ~$350.

2. A universal weld-on which I can have put on locally for $50.

3. A higher quality (high flow?) universal weld-on which I can either buy from the shop that puts it on, or order myself.

What I'm looking at here is a ratio of price to advantage. I'm honestly unaware of the difference in performance of the options, and I'd like any help/insight that anyone has to offer.

Thanks a lot!

James

ps. What differentiates between a Newbie post and one for the perspective forum (E36)?

 

[BigEarl325is]

I just replaced my cat with all-catalytic-converters.com oem replacement and it has worked great. The welds are kinda ugly but it's not like we're ever going to be looking at them. As far as your O2 sensor you should check with your OBD. at the top of this forum you'll see the "Free Diagnostic" post and it'll show you step by step how to check if your O2 sensor is bad. Often times your cats go bad because of an O2 sensor going bad, that's the most common problem. other problems are old age or a poor running engine (burning oil/coolent etc.) As far as your heat shield, is it torn or is there a spot on it (like most of ours) where the area where a skrew goes has deteriorated. What I did is I went to home depot and bought 10 extra large washers and longer screws. This way the washers cover more surface area of the heatshield so that the screw won't tear through it. The longer screws are so that they will be long enough to fit the extra depth of the washer. If I get a chance I'll take a picture of my job to show you what exactly I'm talking about.

You've come to the right place my friend, posting here on the E36 section is the best because that's what kind of car you have and a lot of the problems you might encounter have probably already been encountered.

 

[Pink_Floyd]

I'm not sure how back your heatshield was but mine was rattling like crazy when the car was idling. I put it up on jackstands and took a look underneath. It was very corroded around where the bolts were so it had almost no support. I took some sheet metal and made a few supports for it and bolted it into place. I'm not sure how long it will last but it works great now. Quieter than ever - and it only took me like 1 hour.

 

[BigEarl325is]

Yeah exactly. At idle mine was ok but as soon as i gave it a little gas the heat shield would rattle like crazy. I did it the lazy way, using washers, but basically Pink_Floyd and I fixed it, we didn't buy an all new heatshield. Give that a shot before you spend money you don't need to.

 

[stimmy]

That'll work great, thanks! I'm having a local shop put on the cat as they're not charging me much for labor or parts. I'll do the heat shield and o2's myself. I'm going to repost asking if I need to replace BOTH O2 sensors, or just one. Thanks so much!

 

[BigEarl325is]

Two O2 sensors? Hmm, you said you have a 92 318is. I have no idea there was more than one O2 sensor on that car. The 325 only has one (until 96)

 

[stimmy]

For future referance, the 92 318is only has one cat. I was looking at the wrong diagram in the Bentley.

 

[Willis]

Just a quick question,

What are the benifits/ drawbacks of removing the catalytic converter and running straight pipes?

 

[manuel]

i wouldnt run straight pipes on a bmw...not only will it sound like crap, you will probably loose some backpressure and might not pass emissions testing. now if you had a v8/nice turbo under the hood, go for it. it will be music to your ears.

small mpg of straight pipe gt

 

[stimmy]

The heat shield problem has gotten much worse, and I imagine I could do a quick fix the way BigEarl did, but the supports are SO deterioriated that I don't think it would be worth the effort.

I've four questions about this:

a) How important is it to have a heat shield in the first place? I don't necessarily want to take mine off as I think that'd be more work than fixing it, but I'm just curious, for future referance.

b) Is there a specific place to get new ones, or is that dealer?

c) How did you do your sheet metal job, PinkFloyd? Pictures, as promised?

d) Is there a material better than sheet metal that could be used for a more permanent solution? If this is such a common problem it seems like there'd be a better solution.