Loud exhaust diagnosis

[alvocado]

I'm getting a louder than normal exhaust sound and it seems to be forward in location. I sprayed some soapy water on the exhaust manifold and did a cold start. Soap bubbled where the manifold meets the head at the rear most location on the driver's side and stopped when the manifold heated up (within about 30 secs.)

 

Is it normal for a small amount of exhaust gas to pass the manifold gasket at startup when cold or is the soap bubble a sign that the gasket is allowing exhaust gas to pass once the manifold heats up? With a metal gasket, I assume there is some expansion when hot that would help seal the connection. I'm trying to determine if this is the issue or if the factory exhaust has a leak elsewhere (200k miles on it.) 

 

 

 

[newdude]

10 minutes ago, alvocado said:

I'm getting a louder than normal exhaust sound and it seems to be forward in location. I sprayed some soapy water on the exhaust manifold and did a cold start. Soap bubbled where the manifold meets the head at the rear most location on the driver's side and stopped when the manifold heated up (within about 30 secs.)

 

Is it normal for a small amount of exhaust gas to pass the manifold gasket at startup when cold or is the soap bubble a sign that the gasket is allowing exhaust gas to pass once the manifold heats up? With a metal gasket, I assume there is some expansion when hot that would help seal the connection. I'm trying to determine if this is the issue or if the factory exhaust has a leak elsewhere (200k miles on it.) 

 

 

 

 

 

Any broken manifold bolts?  These LS engines are known for them to break.  Time for bolts and gaskets.

[alvocado]

No broken bolts. I had that on a previous 6.0l and had to remove the head to get the bolt out. It was the bolt closest to the firewall, snapped off just below the head surface and I couldn’t get anything on it. 

[CamGTP]

I've seen the manifolds become not "flat" anymore even if the bolts are not broken. Then once the manifold heats up they seal again, I've also seen them crack underneath but that is more rare.

 

There is a local construction company near me that has about a hundred Chevy 2500/3500 trucks and after 200-250k miles they end up just replacing all the manifolds when they do a major service to the trucks.

[dna9656]

Corrosion can play a part in this too.

[alvocado]

I stand corrected. I missed the farthest back bolt and the head is in fact gone. That explains the leak and the noise. Looks like I'm pulling the exhaust manifold this weekend.

 

For those who've dealt with this, is there any risk the manifold is warped or should it be fine to reuse and simply replace all the bolts and gasket?

[alvocado]

New manifold bolts and a gasket did the trick.

 

The exhaust flange nuts are relentless at being a PIA to get off. I got two off with MAP gas but the one with the worst access rounded and turned into a mess before finally getting some bite with a second bolt extraction kit. That alone burned two hours.