Can't get throttle body to seal to Intake Manifold

[njc1064]

Previous owner was using rtv to seal the throttle body to the intake manifold. After being unable to get the throttle body to seal with the gaskets on the last manifold, i chalked it up to a warped mounting surface and opted to swap the manifold for a known good manifold; i also picked up new gaskets for the throttle body. I applied some copper gasket spray to both sides of the gaskets and attached the throttle body to the manifold. Gave it a few hours to setup and did a boost leak test. It's still leaking from at the top section where the throttle body meets the manifold.

What's the issue here? Could it be that the studs for the throttle body are in the wrong spots, causing an improper seal?

 

[spyderdrifter]

Most likely you have the new gasket on wrong. I made this mistake and had the same result. The gasket has a slight rounded spot on one of the edges. Just line that up with the right throttle body edge and you should be good. I think it goes on the top edge.

 

[kchaazz]

Ive had this trouble before. The solution is to get a 3M sanding block, some 80 grit sandpaper, and block sand the intake manifold surface and both throttle body surfaces. As you sand, the high and low spots will be readily apparent, and once you get the surfaces level, they'll seal fine. This will only take about 15 minutes to do.

 

[spyderdrifter]

However, large grit sandpaper such as 80 grit can leave sanding lines that the gasket may not seal up and still leave a leak. If you do the sanding, go over it after the 80 grit with 120 grit or smoother to blend those sanding lines smooth.

 

[kchaazz]

You could do 120 after the 80 grit, but its really not necessary on a surface utilizing a paper gasket of .03125- .0625" thick, as the gasket material is very homogenous. I have used the method I mentioned in my above post on several setups, and it works flawlessly; youre just making the surfaces level again is all. 120 after the 80 grit certainly wouldn't hurt though if one is willing to put in the time and effort.

 

[Tyeler18]

Like stated your probably putting the gaskets on wrong. Copper seal really shouldn't be used on intake tract gaskets. It does work, but I've found it's better to install them dry. What brand of gasket are you using? The crappy felpro paper gaskets or the OEM gaskets that are metal and have a firing ring?

 

[njc1064]

Ive had this trouble before. The solution is to get a 3M sanding block, some 80 grit sandpaper, and block sand the intake manifold surface and both throttle body surfaces. As you sand, the high and low spots will be readily apparent, and once you get the surfaces level, they'll seal fine. This will only take about 15 minutes to do.

The gaskets were on properly, but, the problem was that the surfaces were not by any means flat. This was most likely caused by using an abrasive disk on an angle die grinder to clean off old gasket material. This was actually my original suspicion.

Once i started sanding the surfaces, it was immediately apparent that that there were some serious low spots on the throttle body mounting surface. After a little sanding, the surfaces were again perfect.

 

[gieri002]

This was most likely caused by using an abrasive disk on an angle die grinder to clean off old gasket material.

Yup, that'll do it. Good to hear you got it to seal!

 

[Kirkamus]

I have used RTV for them before seemed to seal fine before.