The intake manifold to head gasket is leaking (I have an '88) so I am in the middle of putting new gaskets in. I am at the point in the project where it is time to start putting everything back together. Here is my question: Do I put black RTV around the coolant passages? The Haynes manual says to do it; the GM Service manual does not mention anything about it (it only mentions RTV on the front and rear "flat" areas. I am using FelPro gaskets. Also, do I use it around the rear heater hose to intake flange and the thermostate housing?
Should I be replacing anything else while I am this far?
Thanks for your help.

 

Do yourself a favor and go to the Autoparts store and get some of the stuff called "The Right Stuff" its the absolute best RTV I have ever used. The stuff bonds to metal like there is no tomorrow and never hardens completely. It will turn to a flexable rubber, and you will never have oils leaks. Most RTVs become brittle, that is why I use this stuff. It kinda expensive at 12-15 bucks per can, but it goes a long way and you will thank yourself in the long run.

As for your question about the coolant passages, I used a very small amount on both sides of the gasket. If you get the stuff I speak of, put on a very light bead and rub it into the gasket in a circular motion, until you feel it get tacky, then install the gasket, the reason I rub it in, is so it doesn't ooze outall over.

For the front and back of the intake to block. Clean the sufaces real good with acetone, then apply a good bead along the surfaces, making sure to put a little extra in the corners were the maniflod meet the head/block. Again in that area I used my finger to work it in real good. Put the manifold on and troque to specs. In a short time you will see that RTV set up and it will feel just like rubber. In 5 yrs it will still feel the same. :D

 

I called the tech line at Permatex and they recommended Hylomar for this application. That is what I used and it worked great. I also used the "Right Stuff" on the end gaskets which is the best stuff out there. I went a little heavy on the bead and let it set for several days before starting the motor so it would set up properly. Never leaked again :yesnod:

 

Im with the other on using the Right Stuff....I used it on the rear end carrier to reseal it and it hasnt leaked in over 2 years.When the 3.73 rear was installed some time back,the shop used a RTV seal and it began to leak in about 11 months which is why I went with the Right stuff and did it myself.

Will need to do my intake manifold again,the RTV the engine shop used has a small leak in the front. :)

 

As already mentioned, the Right Stuff (Gasket in a Cheeze-whiz can) is great stuff. At $14, it is initially expensive, but really great. It has a very fast service time...as in under 30 minutes and you can be back on the road again.

 

I also used some Black RTV (automotive grade) around the water passages on both sides of the gaskets.

I used Permatex gasket sealer on the steam pipe at the rear of the manifold and on the thermostat gasket and bolt threads as well as on each intake bolt threads and a little on the bottom side of the distributor gasket.

Also, chase the intake bolt threads as well as the bolt holes in the heads to assure good torque readings. You can use tap and dies or a chasing kit available at Sears.