Well the whole summer has focused around swapping the intake on my 90 vette. So far it has turned into a huge head ache. I have a ported Edelbrock base plate that I installed and today when I was installing my second set of SLPs I noticed a small coolant leak on the bottom back hole on the driver's side.

Any idea why this would be leaking or how to stop it? If I pull the intake off again I'm getting heads and cam for it, so save me some money and help me out.

 

Did you install new heads or stockers ?

 

Does the L98 have coolant in the intake? I know the LT-series has a dry intake, so if that's consistent then the problem must be in your heads...

 

Yes, it does have coolant going threw the throttle body, I live in South Florida and eliminated that mess right away. Just remove the coolant hose going into the thottle body on the passenger side. Then remove the small hose from the throttle body to the block. (its the one just above the water pump) Now plug the hose you first disconnected into the block side and your done. My car loves it my operating temps went down 15 deg.
Good Luck!

 

He said the leak is at the back though...although I agree with you on the TB coolant bypass, definitely have that done myself.

 

What do you mean by "bottom back hole on the driver's side" ?

 

Retorque the entire intake with a few extra pounds of torque....if it stops leaking there you go...if not your no worse off.

 

Don't feel too badly, this intake leak thing has been a problem for a lot of guys.

If re-torquing the intake manifold bolts doesn't cure your problem, here's how I do it to insure a no leak situation.

First, all the mating surfaces have to be free of oil and coolant residue.

I then dimple the China Walls on the block using a nail set and I also do the same dimpling on the corresponding areas on the underside of the intake manifold. The little dimples give the silicone sealant (to be applied later) to have something to bite into. I've never actually counted them, but I end up with around 30 dimples at each of the four locations. I have a photo of the dimples if you're interested.

I apply a thin layer of sensor safe silicone sealant on BOTH sides of the intake gaskets. Around all the intake ports and all the coolant openings. Then I set the gaskets in place and lightly press down on them.

I then apply a bead of SSS to the China Walls. I use a 3/8" bead rather than the 1/4" bead you may see in some manuals. I carry those beads up and onto the intake manifold gaskets to seal the areas where the intake meets the cylinder heads/block.

BEFORE the SSS skins over, I set the intake straight down with no back or forth movement. I look through the intake manifold bolt holes to align them with the holes in the heads.

I then install all the intake manifold bolts by hand finger tight with Anti-Seize applied to the threads.. I follow the torque sequence shown in many shop manuals and use at least three steps to bring them all up to 35 ft lbs of torque. The torque sequence differs depending on the engine, so be sure to use the sequence for yours.

I let the intake set for an hour or so, then go over every bolt in the same sequence. It's not unusual to find that one or more has lost torque due to compression of the gaskets. I wait for another hour or so, then go over all the bolts again. I keep doing this until all the bolts hold the torque setting.

If it's done like that, the sucka won't leak.

Hope this helps.

Jake

West Point ROCKS!

 

I just replaced my intake gasket about 6 weeks ago L98 just make sure both sides are clean I used a light coating of RTV on the intake to head gasket both sides and the Right Stuff on the China Walls, also like Jake said you need to extend the sealer from the China Wall up the sides of the new gasket. I also kept the block off plates on the rear of gaskets.
The intake bolts do run into the water jackets I believe. I not sure what hole you mean in the back of intake, if it is the back bolt you might try some thread sealer on it see if it stops, but you really won't be able to tell till you get the motor back up to operating temp.

 

Thanks for all the help guys.

It is actually leaking in one of the bolt holes for the runners. On the Driver's side, the rear most hole for that runner has a small leak. Will retorquing still fix this?

 

Negative...it shouldn't leak there.....I'd be tempted to say that there is a problem with the intake if coolant is coming from a runner bolt hole.

 

There should be no coolant coming from a runner bolt. Unless the intake has some type of internal damage. It is possible to port the intake to much and cut into a water passage, who did the porting work. Which is what sounds like happened. I would also think that running the car would suck coolant into the cylinder for that runner. The front and rear of the L98 intake pass water through it for cooling.

 

Before you tear it all apart, try this; remove the bolt where the leak is and wrap teflon tape around the threads. Put back and tighten it. Now pressure test your coolent system. If it holds pressure, you OK.
My Superram base did this and this is how I fixed it.

 

I also would try to fix it without tearing it down you might get lucky depending on how much damage there is to the intake

 

By just putting a bolt in the hole the leak stops. I purchased it already ported, so I don't have the history on that. Only reason I noticed the leak is because I'm replacing the runners for like the tenth time.

 

engle1147 has a point - coolant doesn't belong there. Coolant in the rear bolt-hole for the runner would suggest a crack between the bolt-hole and the water-passage of the manifold; coolant introduced to the fuel mixture (not good). Coolant in the rear bolt-hole of the manifold to the head would suggest either a leaky manifold gasket or (worst case scenario) a crack between the bolt-hole and the water-passage in the head. If it's a crack in the bolt-hole, a non-hardening Permatex or any good sealant on the bolt will provide a usable fix. The other is obvious - new manifold gasket (a real pain in the @$$, but better).