Catalytic Converters on a 1997 Chevy Z71 K1500 with 5.7L Making a Lot of Noise

Updated 07/13/2015 | Published 07/10/2015

Products Featured in This Question

MagnaFlow Stainless Steel Catalytic Converter - Direct-Fit

(4)

$379.00

MagnaFlow Stainless Steel Catalytic Converter - Direct-Fit

(4)

$663.00

MagnaFlow Heavy Metal Loaded, Stainless Steel Catalytic Converter - Universal

$242.00

Question:

When I bought this truck a couple of years ago the CAT had been removed. I live in an area that requires emissions inspection plus I think its against federal law to remove it ? so the first order of business was to replace it which we did with a magnaflow. Less than 2 years later, the Cat is making all sorts of noise sounds like gravel in the bottom of it during idle. Diagnosis is that the brick in the cat has broken loose. What could cause this? The shop I took it to tried to blame it on the mixture in the truck I think he said too lean, but cant remember or possibly if the cooling system overheated. Well, the cooling systems has not overheated and the truck doesnt show any signs other signs of a mixture problem. Could it just be mfg defect? Also, does/can this series truck have just a single CAT both sides of the exhaust merge prior to the CAT? That is what I remember on this truck will look again when I get home, but the shop is saying both CATs need repairing.

asked by: Jeff S

Expert Reply:

I would think that if it is a manufacturer defect that the issue would have revealed itself earlier than it did. Magnaflow parts do have a limited lifetime warranty though so you could potentially get replacements via a warranty claim.

Damage could occur to the exhaust from excessive heat, physical damage, frequent use of dirty fuel (with a high lead content). Back when leaded gas was still available my dad would use it because it was cheaper, even though the car had a catalytic converter. He would have to take off the converter and knock all of the lead deposits out and then put it back on. So it is possible that the fuel is a factor.

An overly lean condition would mean there is more air than gas but that would likely damage the motor first. You would likely get a check engine light or equivalent before that happened.

The 1997 Chevy 1/2 ton trucks do indeed require 2 catalytic converters. It might be possible to merge the exhaust pipes from the headers to a single path and use one converter but you would have to make sure the converter used could handle it and it would be a custom installation that a shop would have to do.

For a universal converter that fits your truck you would use # MF99004HM. Again you would need 2. And for a direct fit to OEM specs use # MF23453. You would only need one of these.

expert reply by: Michael H