gvns8

I just finished up installing a new exhaust manifold gasket and it is leaking from all parts of it. I had the bolts torqued to what they are supposed to be at 23-24 ft-lbs. With it leaking a lot, I decided to tighten them up to about 29 ft-lbs which made it leak a lot less. I don't know if I should tighten them any more than that though, but need to stop the leak- any pointers? It is a felpro gasket that does not call for using any sealant.

VAMudDauber

Did you do anything to prep the two surfaces?

gvns8

I cleaned them with t.b. cleaner. They looked pretty clean.

VAMudDauber

Did you put a straightedge against the exhaust manifold to make sure it hadn't warped? I warped a header flange once by waiting too long to replace the gasket. It looked just fine until I put the straight edge against it. Not sure if it would happen to a stock exhaust manifold or not being that they are a little beefier. It’s worth checking. It sucks to have to go back through all that work again but it would suck more to snap off a bolt in the head or even worse, pull the threads out of the head.

DFlintstone

What a bummer! Any chance some small thing like a wire or something got caught in there? It wouldn't take much. The gasket is in place, the bolts went in OK?. Gad..that hurts just thinking about it. x2 straightedge.

Silly thought. It had been leaking before? Hope the bolts aren't too long.

gvns8

I am thinking that maybe the gasket wasn't seated right while tightening the bolts. Maybe I will try tightening the bolts a bit more maybe to about 32 ft-lbs to make sure the gasket isn't caught up on a thread or something and then I guess loosen them up again if I get the gasket properly seated.

The reason I decided to replace the gasket was actually only because I removed the intake manifold to get a better look at the exhaust manifold to see if it was cracked. It turned out it wasn't, but the bolts holding exhaust manifold to down pipe were loose, so I tightened them up. I figured it would be a good idea to replace the gasket since I might not get a good seal on the old gasket after removing the intake. When reinstalling the exhaust manifold there was one stubborn bolt that I had to pry the top of the rear manifold bank down to get the holes to line up on so that I could get the bolt in.

I did not put a straight edge on there, but I guess if end up having to disassemble everything again, I will be sure to check that.

VAMudDauber

Oh, I was thinking that you had replaced it because it was leaking at the two mounting surfaces. It's not likely that it is warped then. I have found that it is always easier to work with and avoid problems with pinching the gasket if you take it loose at the downpipe and work with just the manifold. Snug all the bolts down before you start to torque. Start in the center alternating back and forth working your way out to the ends.

jerrys90

I torgued mine to 40 foot pounds. On cool down it would pop and crack for about 2 days and then quit makeing this sound. I used the said felpro gasket. I believe the metal flange on the gasket goes on toward the motor. Did you install correctly? 1990xj 4.0

gvns8

Thanks guys, I agree that having a loose downpipe would have been ideal, but the bolts connecting the downpipe to the rest of the exhaust are pretty much seized. I guess I could loosen up the connection between the manifold and the downpipe/minicats though.

As far as the gasket, mine was all metal (both sides) and a mirror image on both sides. The 01's and 00's are the only ones who had the same style exhaust manifold as mine. Thanks for your input about the bolt torques though jerry90. I have also heard from others that you can easily tighten them to 35ft-lbs without worrying about broken bolts/warped head and that 23 ft-lbs is never enough to make it seal properly. I think that it simply isn't tightened enough- so I will go in there and see if I can tighten the bolts down more to stop the leaks. Hope this works!

jerrys90

I did my torque in stages over one day. torque, run,cool down,torque etc. until I reached 40 foot pounds. No vacuum leaks. jerrys90 xj 4.0

jerrys90

Just remembered- I took out all sensors and vac posts from intake manifold and wraped with vyln tape. hope this helps. jerrys90xj 4.0

gvns8

As a follow up, Jerry90 was right. I did just what he did- tightened up the exhaust manifold a little more after each run/cool down until it stopped leaking. I ended up tightening the bolts around 40 ft-lbs also, and luckily there is no longer a leak. My father does work with jets and the he said usually there is a "running torque" that must be added to the actual torque specification, so I think this may be the same type of thing. In other words you have to tighten up the manifold until it sandwiches the gasket in there, and take the torque it takes to do that and add it to the 23ft-lb (or whatever yours calls for) and that should be your final torque. Not sure if this is true, but it makes sense.

For anyone doing this in the future I highly recommend getting one of these u-joint sockets in 9/16" size.



If I didn't have it this would have impossible to tighten all these bolts without removing all the accessories each time.

Mycherokee96

just out of curiosity, did you tighten them down in the sequence thats called for to begin with? Just askin.....

gvns8

Yes I did.

VAMudDauber

Great tips!