Which replacement CAT?
Thread Starter
Racer
Joined: Mar 2008
Posts: 333
Likes: 18
From: Maple Valley Washington
Which replacement CAT?
Found out I have a bad cat that some of the packing, they suspect has come loose. 2002 C5Z with 25K miles. There is a squealing noise on decal. At first I thought it was the belt so I had the belts, tensioner and idler pulley all replaced. Then they figured out that the sound is coming from the left side Cat. So I need to replace them. Figure I would replace both at the same time. I would like to have them welded in on the stock H pipe. What is the stock size? 2.5inch? 3inch? Found MagnaFlow 59956 for a cheap price of $106 each but are 2.5inch. Is that correct? I don't have the funds for LT's, catted xpipe and a tune currently. :-(
Thanks!!
Thanks!!
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
First off...who is "they" ??...a bad CAT with 25K on the clock is a stretch !!...did you have any driveability issues like loss of power you'd see with a clogged CAT ??...did "they" do a back pressure test to confirm it IS a clogged cat or just guessing ??...left side is real easy to diagnose...you can disconnect the AIR check valve and if you have a "low pressure"pressure gauge...like 0-10 psi you tap into that disconnected line that goes into the exhaust manifold. 2 psi max is the limit. Now $106.00 CATS probably aren't going to last as long as the OEM $2,000 ones but you get what you pay for and when the car starts throwing P0420/0430 DTC's it will be time for new ones again...just sayin' dude !!...and probably a good idea to check fuel trims with a scan tool if "they" have one to make sure the L/H bank isn't running to rich !!...for example and L/H O2 upstream sensor reporting a false "lean" condition (below 450MV).
Last edited by C5 Diag; May 30, 2019 at 05:52 PM.
Thread Starter
Racer
Joined: Mar 2008
Posts: 333
Likes: 18
From: Maple Valley Washington
First off...who is "they" ??...a bad CAT with 25K on the clock is a stretch !!...did you have any driveability issues like loss of power you'd see with a clogged CAT ??...did "they" do a back pressure test to confirm it IS a clogged cat or just guessing ??...left side is real easy to diagnose...you can disconnect the AIR check valve and if you have a "low pressure"pressure gauge...like 0-10 psi you tap into that disconnected line that goes into the exhaust manifold. 2 psi max is the limit. Now $106.00 CATS probably aren't going to last as long as the OEM $2,000 ones but you get what you pay for and when the car starts throwing P0420/0430 DTC's it will be time for new ones again...just sayin' dude !!...and probably a good idea to check fuel trims with a scan tool if "they" have one to make sure the L/H bank isn't running to rich !!...for example and L/H O2 upstream sensor reporting a false "lean" condition (below 450MV).
I appreciate the feedback. Makes me wonder what kind of cats come with the LT header sets you can buy.
Thanks,
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,319
Likes: 3,927
From: Cape Coral, Florida
I took the vette to a shop called Corvettes of Auburn. They do great work. Took them some time to figure out what was causing the sound. They don't think it is clogged, they believe something within is loose which is causing the "sound" during deceleration. I will try and take a vid of it tonight. Seriously sounds like a squeaking belt but from the middle of the car. They were using a mechanics stethoscope to pin point the noise and even took the H pipe off to figure it out. I do not have any drivability issues. Just that annoying loud sound after hitting the gas. LOL. I have also been trying to find a used H pipe somewhere as well.
I appreciate the feedback. Makes me wonder what kind of cats come with the LT header sets you can buy.
Thanks,
I appreciate the feedback. Makes me wonder what kind of cats come with the LT header sets you can buy.
Thanks,
Thread Starter
Racer
Joined: Mar 2008
Posts: 333
Likes: 18
From: Maple Valley Washington
Trust me they did bang on it. But couldn't hear anything. It is only when the engine is running. It is truly annoying as F*ck. I can hear it over my BB Bullets LOL.
