Exhaust Manifold Leak

[crazykyle709]

New to the forums, been lurking around for a while. Recently bought an 07 mustang 4.6l with a major exhaust leak on the bbk shorty headers. Replaced the Header gaskets since the old ones were in pieces. After tightening the bolts from a couple heat cycles it is still leaking between the exhaust manifold and the engine on the drivers side.

Could this possibly be a warped manifold? I have no idea how long the previous owner drove with this leak. Thanks!

 

[Mr. Q]

 

[Mustang Mark]

^this. I used damn near a whole tube of the stuff on my headers. Exhaust leaks drive me crazy.

 

[nawagner]

Did you use OEM gaskets or others? Anything other than OEM will leak in my experience.

 

[JUSTA3V]

Take the header off and put a straight edge on the flange. See how bad it is. I would start there. If the flanges are true you shouldn't need ultra copper. Just use OEM gaskets. I have reused OEM gaskets twice on 2sets of headers and never had to use ultra copper.

Maybe I just got lucky

 

[BruceH]

Try to use oem studs to secure the header. The header bolts supplied with most aftermarket headers will loosen. Locking stage 8 bolts will fix it, so will drilling the heads and lockwiring the aftermarket header bolts after they are properly torqued. Heat cycles don't really apply to mls gaskets but they will loosen bolts that aren't designed for the application.

If the flanges are warped then there are a few options. One is to use stock mls gaskets with orange ultra copper. Anther is to use the Percy gaskets that are made from dead soft aluminum. They will conform to the warpage.

 

[crazykyle709]

^this. I used damn near a whole tube of the stuff on my headers. Exhaust leaks drive me crazy.

Would I apply this between the gasket and the engine block or between the gasket and headers? I actually used some of this on the outside of the headers where the leak was. I used ford racing gaskets from american muscle.

 

[Mustang Mark]

Would I apply this between the gasket and the engine block or between the gasket and headers? I actually used some of this on the outside of the headers where the leak was. I used ford racing gaskets from american muscle.

I did both

 

[crazykyle709]

I did both

Ok, thanks! Think I'll put some on there on Monday. Debating whether or not to replace the bolts too.

 

[NickD87]

I had the same issue this fall, I switched to original ford and after pulling out the fird racing ones no wonder they leak, my mechanic said he wont do any s197 headers now without oem gaskets

 

[Mustang Mark]

I put on new OEM style studs and nuts when I did mine, the bolts you get with headers suck and will back out.

 

[crazykyle709]

Thanks everyone! Decided to order some percy gaskets. I'll let you know how they turn out after I get them installed!

 

[05gtowner]

BBK? There is most likely your problem right there. Buy OEM manifolds or get better quality headers

 

[kwadkins]

I'm all for factory studs on exhaust. Bolts seem to always loosen.

 

[crazykyle709]

Installed the percy gaskets today.... NO LEAK!! Thanks everyone for the suggestions. Now to move on to the annoying whine in the rear axle, I believe there is a TSB for it though.