How to fix exhaust leak

[Tezzmeret]

Originally Posted by Boccaccio

CO and CO2 poisoning would only be a concern if you would run your car inside a sealed area/space (running the car in a garage with the windows down).

A more pressing issue are out of spec fuel trim values due to introduction of unmetered oxygen into the range of the O2 sensor due to exhaust leakage (engine - header, header - overpipe connection).

Plug one of the exhaust tips, stick the hose-end of a shop vac (blower function) into the other exhaust tip, turn on the vac and spray soapy water onto the aformentioned connections (spray it also on the overpipe - frontpipe connection or other areas you might suspect an exhaust leak is present).
Bubbles present --> leak --> fix the leak.

Appreciate this, I confirmed it wasn't an exhaust leak thankfully, but still have no clue what the sound is. So I'll be having fun figuring that out lol

[Ads]

Jumping in on this relevant thread. I am in the process of trying to eliminate leaks from my exhaust system and am running into many conflicting opinions in terms of the use of gaskets and/or sealants, even within this very thread.

So far I have discovered evidence of a leak between a 2 bolt flange/flat gasket and would like to fix it up the right way. The flanges/join was misaligned (while still bolted tight) when I found it, so I am hoping that is the main reason for the leak. Either way, I wanna do it right when I replace the gasket. The flange surfaces are fairly flat, although not perfect. I have made sure to clean them up nicely.

So the question is;

a) Gasket only
b) Gasket + Spray-A-Gasket Sealant (or other high temp gasket sealant/dressing)
c) Gasket + Copper RTV Silicone Gasket Maker
d) Copper RTV Silicone Gasket Maker only
e) None of the above

Many people on various forums seem to recommend/swear by using a gasket + copper RTV gasket maker as your best bet to hold off any leaks. However Permatex themselves specifically state that this is incorrect:

10. Using a gasket maker as a dressing on a conventional gasket.
This might be the most common gasketing error of all. Many mechanics will use an RTV gasket maker to hold a conventional or cut gasket in place during assembly. Some mechanics will even use the RTV gasket maker as a dressing, coating both sides of the gasket. Gasket makers are the wrong product for these applications – their formulations are too thick for use as a dressing. If you’re installing a conventional gasket, use a gasket sealant – they’re available in sprays, liquids, and tubes, with specialized formulas for a variety of applications. Source

Even so, the Ultra Copper RTV GM is only rated to 700F/370C and the sealant even less. As Grady pointed out, temps can reach well above that under high speed/rpm, especially a modded engine on a track day for example. Though Permatex suggest both are suitable for exhaust manifold/header applications.

So, colour me confused... Should I just shut up and take my pick and see how it goes?

I have looked at the thicker Remflex gaskets, although they don't seem to be readily available in Oz for a reasonable price.

[Ashikabi]

Originally Posted by Ads

Jumping in on this relevant thread. I am in the process of trying to eliminate leaks from my exhaust system and am running into many conflicting opinions in terms of the use of gaskets and/or sealants, even within this very thread.



So far I have discovered evidence of a leak between a 2 bolt flange/flat gasket and would like to fix it up the right way. The flanges/join was misaligned (while still bolted tight) when I found it, so I am hoping that is the main reason for the leak. Either way, I wanna do it right when I replace the gasket. The flange surfaces are fairly flat, although not perfect. I have made sure to clean them up nicely.



So the question is;



a) Gasket only

b) Gasket + Spray-A-Gasket Sealant (or other high temp gasket sealant/dressing)

c) Gasket + Copper RTV Silicone Gasket Maker

d) Copper RTV Silicone Gasket Maker only

e) None of the above



Many people on various forums seem to recommend/swear by using a gasket + copper RTV gasket maker as your best bet to hold off any leaks. However Permatex themselves specifically state that this is incorrect:





Even so, the Ultra Copper RTV GM is only rated to 700F/370C and the sealant even less. As Grady pointed out, temps can reach well above that under high speed/rpm, especially a modded engine on a track day for example. Though Permatex suggest both are suitable for exhaust manifold/header applications.



So, colour me confused... Should I just shut up and take my pick and see how it goes?



I have looked at the thicker Remflex gaskets, although they don't seem to be readily available in Oz for a reasonable price.

I believe permatex is referring to oil/liquid gaskets in their statement. Exhaust gaskets are a little different. In your case, it sounds like you have an imperfect flange mating surface. Exhaust gaskets aren't very flexible for dealing with irregularities like that. I believe using a metal exhaust gasket as a "filler" with some copper permatex will get you the best result. Just make sure everything is clean.

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[Spawn_Of_Creation]

The ace headers are known for the bolts backing out, especially the overpipe from the main header.

I've seen alot of people recommend high temp locktite for the bolts.

Also make sure after heat cycling a few times after install to tighten everything back down again.

[Ads]

Originally Posted by Ashikabi

In your case, it sounds like you have an imperfect flange mating surface. Exhaust gaskets aren't very flexible for dealing with irregularities like that.

I am assuming it became misaligned due to copping quite a few knocks when the car was very low and it may have slowly shifted. I have tested it and it seems to want to mate up fine, though I will see how it goes once everything is torqued up.

I believe using a metal exhaust gasket as a "filler" with some copper permatex will get you the best result.

Yeah I was leaning towards this as my best bet to fill any possible gaps. As I said, the flange surfaces are ok but not perfect. Roughly 0-1mm out from an initial look.

Originally Posted by Spawn_Of_Creation

Also make sure after heat cycling a few times after install to tighten everything back down again.

Yep, I will be sure to do this after waiting 24 hours for the UC Silicone to fully cure to double check the torque is still good.