Blown Exhaust Gasket, without being blown?

GoldenMotor.com

dodge dude94

New Member
Jun 8, 2012
1,017
1
0
East Texas
Between school and sickness, I haven't been riding much. Here lately I've noticed the usual black crap on the case underneath the exhaust flange. Usually indicative of a blown exhaust gasket, but unlike my last two, this one doesn't even look breached in anyway. I checked the torque on the nuts, they're tight. Checked the head, it's tight. Anyway to keep this from happening, AGAIN?
I am wondering if some ultra black RTV might be in order...

Thanks.
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
The exhaust flange is probably warped and not allowing a good seal. They warp during the welding process at the factory. Even with the fasteners tight there can be leakage.

You can check for this by running the gasket surface of the flange against sand paper laying on a known flat surface, glass is best, and the high and low areas will quickly be noticable.
Sand until it is absolutely flat. Also check the cylinder gasket surface for any irregularities then use a gasket made from material meant for exhaust. Preferably at least 1/8" thick and torque the fasteners to 60 inch pounds and check them again after the engine has run a couple of times.

Tom
 

dodge dude94

New Member
Jun 8, 2012
1,017
1
0
East Texas
The exhaust flange is probably warped and not allowing a good seal. They warp during the welding process at the factory. Even with the fasteners tight there can be leakage.

You can check for this by running the gasket surface of the flange against sand paper laying on a known flat surface, glass is best, and the high and low areas will quickly be noticable.
Sand until it is absolutely flat. Also check the cylinder gasket surface for any irregularities then use a gasket made from material meant for exhaust. Preferably at least 1/8" thick and torque the fasteners to 60 inch pounds and check them again after the engine has run a couple of times.

Tom
Gotcha. Where can I get gasket material like that? Parts store?
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Gotcha. Where can I get gasket material like that? Parts store?
Dodge,
Yes, any good auto parts store should carry gasket material in various thickness. Tell the counterman that it will be used for exhaust. If he's worth his weight he'll be able to help you.
Industrial suppliers such as Grainger and Tractor Supply will also have gasket material.

Just a hint: When you remove the exhaust from the engine, clean the gasket surface welll and 'paint it' with a magic marker or something similar. Now when you run the flange across the sand paper you'll very quickly see what needs to be done to make it flat. The ink will be sanded off immediately from the high spots and still be visible where the surface of the flange is low. The warp will be evident.

Tom
 

dodge dude94

New Member
Jun 8, 2012
1,017
1
0
East Texas
Dodge,
Yes, any good auto parts store should carry gasket material in various thickness. Tell the counterman that it will be used for exhaust. If he's worth his weight he'll be able to help you.
Industrial suppliers such as Grainger and Tractor Supply will also have gasket material.

Just a hint: When you remove the exhaust from the engine, clean the gasket surface welll and 'paint it' with a magic marker or something similar. Now when you run the flange across the sand paper you'll very quickly see what needs to be done to make it flat. The ink will be sanded off immediately from the high spots and still be visible where the surface of the flange is low. The warp will be evident.

Tom
Coolio. I was gonna try and go to O'Reilly's tomorrow anyhow, so I'll see if they have any.

From what I remember, my flange is pretty ugly, would it be advised to take a metal file and file it down a bit, then sand it?
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Coolio. I was gonna try and go to O'Reilly's tomorrow anyhow, so I'll see if they have any.

From what I remember, my flange is pretty ugly, would it be advised to take a metal file and file it down a bit, then sand it?
Whatever it takes to get the flange to fit flush with the cylinder exhaust port. File, sand, grind. I use a bench mounted belt sander but I realize everyone doesn't have one. If the warp isn't too bad you can use the flat surface with sandpaper. Start with a course grit and work down.

A file will work too just make sure to keep the file pressed flat against the surface and check your progress by painting the flange with magic marker and checking to see that the surface is uniform.

This same method can be applied to the intake manifold flange to assure that it lays flush too. The cast aluminum manifolds are usually pretty good but the welded steel ones that have been chrome plated suffer from the same warp as the exhaust flange. They will usually benefit from some lapping too to get a good gasket surface.

Tom
 
Last edited:

dodge dude94

New Member
Jun 8, 2012
1,017
1
0
East Texas
Whatever it takes to get the flange to fit flush with the cylinder exhaust port. File, sand, grind. I use a bench mounted belt sander but I realize everyone doesn't have one. If the warp isn't too bad you can use the flat surface with sandpaper. Start with a course grit and work down.

A file will work too just make sure to keep the file pressed flat against the surface and check your progress by painting the flange with magic marker and checking to see that the surface is uniform.

This same method can be applied to the intake manifold flange to assure that it lays flush too. The cast aluminum manifolds are usually pretty good but the welded steel ones that have been chrome plated suffer from the same warp as the exhaust flange. They will usually benefit from some lapping too to get a good gasket surface.

Tom
Awesome. I guess I'll try to get at that next week if I can get gasket material.
As far as the intake, I'm not having any issues with it at all. Shoot, I can't even get it off if I try. :S