Exhaust Manifold Leaks… What Now?

[LaGrasta]

I put a new manifold on a few months ago and all was well. I couldn't believe how much quieter the car was. My old manifold was cracked and warped.
I used a new gasket of course, as well as some new grade 8 bolts and zinc lock washers from the hardware store. After about two additional retorques, the bolts seem to be tight. I, however can't get to the lower bolts since the a/c & alt brackets are in the way. I assume they have loosened because the exhaust is loud again.
I didn't want to spend so much for ARP. Are they my only choice?

 

[matt1967]

ARP is only stronger, there going to loosen up just as quick. try some thread locker

 

[jamyers]

Yup, try some threadlocker, and even though they're a pita, you'll want to keep after those hidden bolts for the first couple of heat cycles.

I'm not sure, but Grade 8 bolts might not have the stretch that a lower grade bolt has...any experts got a comment on that?

 

[XFlow_Fairlane]

don't use split style lock washers. once they heat cycle they loose their spring.

you need to use the star ones.

 

[LaGrasta]

okay, then I guess I'll just pull 'em out, insert new star washers and coat 'em with thread locker (high temp type, I expect).

 

[powerband]

Good suggestion on the star washers. I don't use the loc-tite but star washers seem to do the trick on Headers. .

A few people have mentioned in the past the importance of the bracket/brace that clamps the engine pipe just below the manifold tight to the engine to prevent manifold loosening and cracking. Many cars lose this part with exhaust and head repairs. My Wagon doesn't and sure enough - the manifold is cracked. The stock exhaust flexes considerably with engine torque movement and the clamp limits movement at the manifold.

With Headers I always use stainless steel flex pipes after the collectors to permit the exhaust system to "float" referenced to the body and engine.

Powerband 8)

 

[falcon60]

Others may have good luck,but I never run gaskets on the exh manifold if I can possibly help it. They relax (squish a bit),the bolts are then loose and the escaping exhaust erodes the gasket and you have a permanent leak. At that point tightening the bolts just tends to warp the manifold.
If the head surface is good,use a light coat of exhaust sealer (the silica-based stuff not RTV) and install the manifold.Since the silica is "sand" it won't relax or squeeze out,still fills small gaps and imperfections in the surfaces and the bolts stay tight.I just use grade 5 bolts and never have a problem.
Granted,if the surfaces are in bad shape you are stuck with a gasket. Hopefully they are fairly good.Ford didn't use a gasket originally.......

Terry

 

[XFlow_Fairlane]

funny things is my 92 didn't have a brace on it. still had remants of the factory style locks under the bolts. no cracks (I ran it for about 30K with no brace and no problems) I would even run on the interstate for 4.5 hours non stop (top off tank and drive until it died (top off with a couple gallons in the trunk to get me where I was going) I stopped a couple times mid trip to top off oil at night....mani was glowing RED and no cracks in mine,

 

[wallaka]

...Anybody can get lucky. Doesn't mean it's the norm.

 

[fordconvert]

I have been told it is very bad to use regular grade 8 hardware on a cast manifold. I dont remember the details other than it having something to do with the differnt expansion rates between the bolts and the manifold. It either wrecked the bolts or made the manifold loose or both. I just did it the easy way and spent the $20 on a set with some special washer things that are supposed to do the trick as far as keeping things tight.

These are the ones I got for the 200 and other engines and I have never had a leak or issues getting them back out.

http://www.mustangsunlimited.com/itemdy ... y=EMUSTANG

 

[grocery getter]

if you re-torqued all bolts except the ones behind the brackets. you'll have more problems than if you just left it alone.

 

[wallaka]

Those are the correct part, that's for sure. The star washers work OK but these are better.

 

[JackFish]

Mike has these:
http://www.classicinlines.com/headerbolts.asp?cat=16

 

[LaGrasta]

So many opinions…

I think maybe I'll try star washers and the exhaust sealer (silica-based) since you say Ford did it that way.

 

[fordconvert]

Mikes bolts look cool if you were running headers, but they are not long enough for a stock cast manifold.