Intake maifold leak problem

96 T&C, 3.3 engine

I had to replace the front cylinder head last weekend. Got everything
buttoned down and connected and the thing started up and sounds great.
Only problem is the engine is idling at around 1300 rpm. Discovered
that there is a leak at the intake manifold edges and also at the
plenum gasket.

I put new gaskets on and followed the All Data isntructions. There was
a bag off rubber o-rings that I couldn't find any mention in the
assembly instructions so I didn't use them. Now I'm thinking that these
o-rings are the cause of the air leaks.

But where on the bolts do the rings go? Under the bolt head or between
the manifold and the cylinder head. If the latter, how do you keep them
in place while installing the manifold. I doubt they would go there
since they would keep the manifold from a flat contact with the head.

Also, other than adding sealant where the heads meet the block ,
there's nothing that says I should use any kind of gaslet sealer on
these gaskets. Should they go on dry or would a thin layer of sealer
help?

Any advice would be greatly appreciated.

 

Those o-rings might be for the injectors...usually included in an intake
manifold kit.

Intake manifold gasket should not need sealant. Hopefully you're using OEM
parts. If not.....?

Also, each side's gasket may be "slightly" different. Check that.

Bolt torque order and ft-lb specs are important with these gaskets.

Is the "replaced" head "new" or did you machine and reinstall the old one?
Either way, there might be enough of a height discrepancy between the front
and back for a leak.

"Peter Kemp" wrote in message

96 T&C, 3.3 engine

I had to replace the front cylinder head last weekend. Got everything
buttoned down and connected and the thing started up and sounds great.
Only problem is the engine is idling at around 1300 rpm. Discovered
that there is a leak at the intake manifold edges and also at the
plenum gasket.

I put new gaskets on and followed the All Data isntructions. There was
a bag off rubber o-rings that I couldn't find any mention in the
assembly instructions so I didn't use them. Now I'm thinking that these
o-rings are the cause of the air leaks.

But where on the bolts do the rings go? Under the bolt head or between
the manifold and the cylinder head. If the latter, how do you keep them
in place while installing the manifold. I doubt they would go there
since they would keep the manifold from a flat contact with the head.

Also, other than adding sealant where the heads meet the block ,
there's nothing that says I should use any kind of gaslet sealer on
these gaskets. Should they go on dry or would a thin layer of sealer
help?

Any advice would be greatly appreciated.

 

Thanks for the quick reply.

There are 12 o-rings and there are 12 bolts total on the manifold and
plenum. There are only 6 injectors which makes me think the rings are
for the bolts. The head was new and the gasket is a one-piece metal
unit that covers both heads and the valley in between. I followed the
torque specs and the pattern when installing.

The really weird thing is there's a leak around the plenum gasket. Both
of the surfaces were clean and flat and the fiberboard gasket should
have done its job.