2009 Gmc Sierra 6.2l Exhaust Flex Pipe Issues

Davidg159 · November 18, 2009

2009 gmc Sierra 6.2L

I have been hearing strange sounds coming from, what I have isolated to, the flexpipe in the exhaust system. It sounds like the accordian pipe and the external metal mesh are rubbing at certain rpms, creating this "sheen" like sound. Like two very lite metals rubbing together. This sound happens most often in 6th gear, just as I pass through 40mph. As I let off the gas and lose the tension of the engine and let it fall back through 40mph it becomes very apparent. I don't completely let off the gas so it isn't caused by the road surface, it is more based on subtle vibration or harmonics of the engine.

I took it to a muffler shop and they told me these flex pipes are junk and I should remove it or I will have to in the future anyway.

I understand these have been designed to minimize the jolt to the exhaust manifolds lessoning the likely hood of cracks and malfunctions.

Can I get away with cutting it out and replacing it with straight pipe? Or will I really have problems? And will removing this create warranty issues.

Does anyone have any advice?

C. Charles Hahn · November 18, 2009

My advice is it's a 2009 truck with a warranty... take it to the dealer and have them fix it unless you are planning to replace the exhaust with an aftermarket setup.

Spurshot · November 18, 2009

I'm betting it's the cats, not the flex joint.

Davidg159 · November 18, 2009

I'm betting it's the cats, not the flex joint.

Thanks for the feedback.

Something I left out:

I installed an aero muffler recently but kept all the stock exhaust components. We cut the oem muffler out and welded in the aero. Now, the angle of the pipe might have changed ever so slightly but I am talking tiny, if any. Also all the hangers a vertical so there is no additional length or reduction of length that would compress or extend the accordian. I figured the flex would be forgiving of any subtle changes.

Sorry I didn't mention this in the first post, got tired of punching keys on this phone.

What makes you think it could be the cats?

66nova · November 18, 2009

My question is, did it do it prior to installing the muffler?

I have never heard of anyone have a "noise" from the flex pipe. Not saying that it's not the problem, but I have been around a lot of truck with a flex pipe installed

I would just want to be sure that the exhaust shop isn't trying to pass the blame.

Davidg159 · November 18, 2009

My question is, did it do it prior to installing the muffler?

I have never heard of anyone have a "noise" from the flex pipe. Not saying that it's not the problem, but I have been around a lot of truck with a flex pipe installed

I would just want to be sure that the exhaust shop isn't trying to pass the blame.

There was no sound prior to the muffler being installed. And just to clarify, the flexpipe was part of the stock exhaust... Are you familiar with the piece that GM is putting on these exhaust systems. It is like an accordion tube encased in metal mesh, like a weaved hat but with larger gaps... any ideas?

66nova · November 18, 2009

My question is, did it do it prior to installing the muffler?

I have never heard of anyone have a "noise" from the flex pipe. Not saying that it's not the problem, but I have been around a lot of truck with a flex pipe installed

I would just want to be sure that the exhaust shop isn't trying to pass the blame.

There was no sound prior to the muffler being installed. And just to clarify, the flexpipe was part of the stock exhaust... Are you familiar with the piece that GM is putting on these exhaust systems. It is like an accordion tube encased in metal mesh, like a weaved hat but with larger gaps... any ideas?

I am very aware of the flex pipe that is installed from the factory. I have never heard of one causing a sound/vibration. Again, I have not physically heard or put my hands on your truck so I can't say that it's not the flex pipe. It justs does not seem like the likely culprit to me. I am basing this on a few things...

1. There are countless numbers of trucks that are running the factory flex pipe with a 100,000+ miles on them.

2. It wasn't making the sound before the muffler change and now it is.

3. Most of your aftermarket kits come with a flex pipe (Including Corsa one of the best quality exhaust you can buy) that looks almost identical to the factory one.

I'll say it again, could it be the flex pipe, absolutely. I just have my doubts. It's a 2009, I would take it to the dealer before I cut out anything.

Are you sure it is just not a "drone" due to the new muffler?

Davidg159 · November 18, 2009

My question is, did it do it prior to installing the muffler?

I have never heard of anyone have a "noise" from the flex pipe. Not saying that it's not the problem, but I have been around a lot of truck with a flex pipe installed

I would just want to be sure that the exhaust shop isn't trying to pass the blame.

There was no sound prior to the muffler being installed. And just to clarify, the flexpipe was part of the stock exhaust... Are you familiar with the piece that GM is putting on these exhaust systems. It is like an accordion tube encased in metal mesh, like a weaved hat but with larger gaps... any ideas?

I am very aware of the flex pipe that is installed from the factory. I have never heard of one causing a sound/vibration. Again, I have not physically heard or put my hands on your truck so I can't say that it's not the flex pipe. It justs does not seem like the likely culprit to me. I am basing this on a few things...

1. There are countless numbers of trucks that are running the factory flex pipe with a 100,000+ miles on them.

2. It wasn't making the sound before the muffler change and now it is.

3. Most of your aftermarket kits come with a flex pipe (Including Corsa one of the best quality exhaust you can buy) that looks almost identical to the factory one.

I'll say it again, could it be the flex pipe, absolutely. I just have my doubts. It's a 2009, I would take it to the dealer before I cut out anything.

Are you sure it is just not a "drone" due to the new muffler?

It is definitely not a drone. Sounds like metal. And if you look at the way the accordion pipe shimmys within the weave, it sounds just the way it looks. Thanks for the feedback. Also, keep in mind, it isn't a constant thing, it happens only during a certain range in the mph/rpms (see first post).

Could a severe angle caused from the placement of the new muffler cause issues with the flexpipe? Thanks for your feedback.

bluesrefugee · November 18, 2009

Are you SURE that it isn't the Catalytic Converter? I know that it is a newer truck but they can still fail. When the cat in my 94 dodge failed it exhibited the exact same symptoms as you are mentioning (high frequency "metal-on-metal" vibration/rattling). I kept on driving it and the converter eventually melted and plugged up my exhaust, limiting the engine to about 2500rpms or so.

Flex pipes can be a point of failure, though. One broke on my Pontiac and man that thing got LOUD in a hurry.

Davidg159 · November 18, 2009

Are you SURE that it isn't the Catalytic Converter? I know that it is a newer truck but they can still fail. When the cat in my 94 dodge failed it exhibited the exact same symptoms as you are mentioning (high frequency "metal-on-metal" vibration/rattling). I kept on driving it and the converter eventually melted and plugged up my exhaust, limiting the engine to about 2500rpms or so.

Flex pipes can be a point of failure, though. One broke on my Pontiac and man that thing got LOUD in a hurry.

John, this is very interesting. I had planned to take it in this weekend and have the oil changed, tires rotated, etc. Can they diagnose this easily?

ryan_hermanutz · November 18, 2009

I doubt it's your cat, your power would be greatly decreased and you would be throwing a CEL. It probably is your flex pipe, when you got your exhaust put on they probably were twisting you pipes on and then when it got welded in it stayed like that. If it did get twisted it would explain the weird sounds and why you have pinpointed to there.

Davidg159 · November 18, 2009

I doubt it's your cat, your power would be greatly decreased and you would be throwing a CEL. It probably is your flex pipe, when you got your exhaust put on they probably were twisting you pipes on and then when it got welded in it stayed like that. If it did get twisted it would explain the weird sounds and why you have pinpointed to there.

Do you think it would be pretty easy to have them cut the exhuast, let the pipe go to it's most natural position and then weld it back?

bluesrefugee · November 18, 2009

A blown-out, melted or carbon-clogged cat will cause power loss and CEL, but if the ceramic catalyst has simply cracked or come partially loose from the housing there will be a rattle, with no other obvious symptoms. Give the cat a couple of firm taps with a rubber mallet (not hard or you risk damaging the ceramic honeycomb if it isn't damaged already). If anything sounds loose or rattles then you have a faulty cat.

ryan_hermanutz · November 18, 2009

I doubt it's your cat, your power would be greatly decreased and you would be throwing a CEL. It probably is your flex pipe, when you got your exhaust put on they probably were twisting you pipes on and then when it got welded in it stayed like that. If it did get twisted it would explain the weird sounds and why you have pinpointed to there.

Do you think it would be pretty easy to have them cut the exhuast, let the pipe go to it's most natural position and then weld it back?

Perhaps they could, but your muffler shop has already stated that it's junk and worthless so I doubt they would do it without charging you. So maybe look into another shop and see if they are a little better to deal with?

ryan_hermanutz · November 18, 2009

A blown-out, melted or carbon-clogged cat will cause power loss and CEL, but if the ceramic catalyst has simply cracked or come partially loose from the housing there will be a rattle, with no other obvious symptoms. Give the cat a couple of firm taps with a rubber mallet (not hard or you risk damaging the ceramic honeycomb if it isn't damaged already). If anything sounds loose or rattles then you have a faulty cat.

But it's not a rattle, so based on his description I really doubt it.