Exhaust manifold gaskets not holding.

[aficio580]

I have a 97 chevy pu with the 4.3L v6. The engine was rebuilt recently but since I got it back from the shop the exhaust manifold gasket on the left rear cylinder started leaking. I replaced with a felpro gasket but then a week later the right side front cylinder gasket started leaking too. Replaced that and a month later the right front cylinder gasket leaked yet again. Replaced and retorqued bolts after engine was heated. Now it seems as if the left side has started to leak again. Ive been told that some of these engines do not require gaskets on the exhaust. Not sure if mine fals in that category. All exhaust parts and heads are still factory original. No other know issues, no check engine errors. Did not use any sealer on new gaskets.
What an I doing wrong???

[j cAT]

what was the torque used ? bolts new? threads coated with anything ? torque pattern used ? cleaned the bolt holes out ?

[aficio580]

I didnt use any specific torque or pattern except to tighten all a little at a time starting in the middle. Using my best judgement I dare not tighten them any more than what they are now. I did clean the bolts off but they were pretty clean to begin with. Did not coat them either.
Didnt realize an exhaust manifold needed such specific attention. They are not new bolts. They are not working loose either.

[j cAT]

Originally Posted by aficio580

I didnt use any specific torque or pattern except to tighten all a little at a time starting in the middle. Using my best judgement I dare not tighten them any more than what they are now. I did clean the bolts off but they were pretty clean to begin with. Did not coat them either.
Didnt realize an exhaust manifold needed such specific attention. They are not new bolts. They are not working loose either.

if the exhaust manifold bolts are 1997 , you do not use a torque wrench ,and you have leaks the bolts should be replaced. a bolt can only take so much stress then it can no longer maintain a constant amount of force to hold down a component. head bolts normally are replaced at each removal because of this as well.

when the exhaust manifold is removed/installed you need new gaskets. the bolt holes are cleaned and you use medium lock tight to the threads. you torque the bolts first pass at 11ft lbs. starting from the middle work toward the ends. 2nd pass 22ft lbs same proceedure. the two end bolts are the last to be torqued. this is not done with a hot engine !

if this fails your gonna need good exhaust manifolds . just like a head this may be distorted.

[danielsatur]

Have a back pressure test done on your catalytic converters, so you can rule out a plugged exhaust system, it's possible that heat could of damaged gaskets.

[aficio580]

Ok Tnxs. Ill try some new bolts and lock tite and see what happens. The original bolts were still good and tight when the leak started. It started with what sounded like a small pin hole making a ticking noise and grew progressively worse. Also the gasket that leaked was on the port that sits appart from the other two. the leak happened the same way on both sides. Im almost 100% certain there is no excessive back pressure. The engine runs too strong and the exhaust flow out the back is good and strong.

[j cAT]

Originally Posted by aficio580

Ok Tnxs. Ill try some new bolts and lock tite and see what happens. The original bolts were still good and tight when the leak started. It started with what sounded like a small pin hole making a ticking noise and grew progressively worse. Also the gasket that leaked was on the port that sits appart from the other two. the leak happened the same way on both sides. Im almost 100% certain there is no excessive back pressure. The engine runs too strong and the exhaust flow out the back is good and strong.

don't forget the torque wrench.