Clogged Cat 2004 Olds bravada - need magnaflow part # please

[gladesteen]

Hello GM Gurus,

I have more than likely a clogged cat in my 04 Bravada / 4.2 V6.

Last fall i had a BAD missfire from #1 and i promptly swapped it out, but i did have to drive it about 15 miles to limp home. After that, the idle and driving were fine but i started getting awful gas mileage and it would "fall on its face" if you hit the pedal hard ...say passing someone on highway for example. All these things seem to point to a clog.

I've done my research and people seem to recommend the Magnaflow cat. My Bravada does not have the bolt-on cat as some have in Trailblazers. Mine would have to be cut out and welded back in.

Could anyone please give me a good part # for the correct replacement Cat if you know? I've tried looking on Amazon and other places and there are numerous ones to choose from.

Thank you,
Mark

 

[Tiggerr]

Not sure why you'd think your CAT is different than the rest but it should bolt to the manifold and to the front of your muffler like all the rest do...mechanically these trucks are all the same

Here's the direct fit magnaflow:

https://m.summitracing.com/parts/flo-2010024

 

[gladesteen]

Tiggerr,

I originally went that route and ordered the whole pipe/Cat assembly.
The issue is that the crossbrace on Bravada is bolted AND riveted to the frame. I took it to an exhaust shop and they showed me the issue. They would have to cut the brace and re-weld it back together. Its not something i want to do and they dont recommend it either.

What i'm looking for is ONLY the Cat part #, not the whole pipe with catalytic converter. Hope that makes sense. The exhaust shop said they would cut and re-weld the Cat back in for me for $300 total.....just trying to see what Cat works best for our trucks.

Thanks,
Mark

 

[Mooseman]

You basically mean a universal cat to weld in to the existing pipe. Ours is an oddball 2.75". However, looking on Magnaflow's site, they list two numbers under "federal". Part # 99006HM and Part # 51006 (OEM grade)

Both of them show in the specs they are 2.5". It may not sound like much but GM did get this exhaust system right and is pretty free flowing. May also be an issue when welding it in.

I have no idea what crossmember you're referring to but all GMT360 are the same. I have replaced the cat myself and had no issues. You unbolt from the manifold, unbolt from the rear pipe, unhook the hanger, pull down. The biggest problem is sometimes the studs break in the manifold, which means a lot of times, having to pull the manifold, which then means broken manifold to head bolts. Maybe the mech is just trying to avoid all that and just cut and replace. However, he should be able to avoid seized/broken studs by heating them up with the torches first.

I'd try welding in a 3" instead. The welder may have to be creative though. I'd also get a second opinion.

 

[gladesteen]

Mooseman,

There is a big crossbrace that ties to the frame on each side.
The crossbrace sits directly under the pipe, but the Cat is accessible / open and the guys at the exhaust shop say they do them all the time. Cut it off, weld a new one in.
The full pipe w/Cat and flanges would never get in where it needs to go without cutting the cross brace out. I've read that Trailblazers have this crossbrace also, but it seems you can just unbolt and remove it. Mine is also held in place with large rivets.

Mark

 

[Mooseman]

OK, did a bit of research and there is a difference between the EXT and shorties, which apparently does make a difference (I had changed the one in my old EXT, still original in my '07 LS). Here's the info I got from the OS:

http://forums.trailvoy.com/showthread.php?t=89459&page=2

I just did the cat on my 2004 LS trailblazer. Sucked getting the OEM cat out. Unless you have a sawzall. The top nut thats on the engine side of the cat is easiest to take out going through the wheel well. The others are easiest from under the car and a 15mm deep socket and a very long extention. To get the muffler out of the way, I pulled it off the rubber bushing, and on my TB there is a small bar going across from one side to the other. I unscrewed the 1 bolt from one side and pushed the bar out of the way and let the muffler move to the side toward the drive shaft. I then had enough room to get the cat pipe brace out of the rubber bushings. I used a sawzall to cut the cat pipe in half. I cut right after the cat, cause the cat was the reason I couldnt pull the pipe out the back. I didnt want to do all the transmission jacks and wood blocks, So I went this route. The new magnaflow direct fit cat went it perfect without a problem. Magnaflows cat is flat, unlike the round OEM cat, making it slide right over the frame. The tricky part for me was the top pipe connection has a metal seal. Dang what a pain! I stuck one hand in and held the seal and collar, and the other with the 15mm deep socket and LONG extentions, I slowly screwed on the nuts. I am at 83,000 miles and can notice a huge change when driving. Gained a lot of horsepower back. I will see next tank of gas if I am getting better mpg.

So it can be replaced with the pipe unless you are replacing it with an OEM (yeah, right!). We can't advise you really on which universal to use to weld in, just a best guess.