Intake Gasket Advice

Hi guys!

Well i have been getting coolant loss for some time now. I thought that when I replaced the radiator due to a broken lower outlet, the adding of coolant would be resolved.
There is also oil at the front, drivers side lower intake manifold area as well.

I will replace the lower intake manifold due to a snapped off thermostat bolt.
My friend insisted on an easy-out, and I told him not to torque it enough to break it..Well, anyway, I had to use JB weld to rebuild the corner with a heli-coil.

JRS3800+ LMP, any new style gaskets available for the L27? Any advice on the plastic plenum or lower intake tips? I only work on my GTX or Transport when I have to these days.... I am wearing too many different hats...cheers KEV

Wow Kev you got your hands a bit full....

Being that you have a 95 L27 I recommend that you replace the upper intake, when you remove the upper intake you will understand why, could also be a coolant consumption issue or part of it... Both Dorman and Delphi make a replacement for this..

The lower intake gaskets.... I would recommend Fel Pro for those... There is nothing better for the L27 TPI then what they sell...


If you are going to dig into this let me know and I'll toss in some pics as there are some things I would want you to do for a good seal and a dry motor...

Being that you have a 95 L27 I recommend that you replace the upper intake, when you remove the upper intake you will understand why, could also be a coolant consumption issue or part of it... Both Dorman and Delphi make a replacement for this..



If I am not wrong the 1993 TS 3.8 has a upper intake manifold made of alloy. If I am right, is it an option to get one from a 93´to use for a 95´? Will it fit?

Reason for asking is that it is easier and cheaper for me to get one from the scrap yard.

Our 95 Transport 3.8 now has 158K miles. I have had 2 constant fluid leakage issues with this van over the last couple of years.
I was losing about a quart of oil to the ground about every 3 weeks. I searched a number of reviews and found that CD-2 oil leak seal had good ratings. So far, this product really seems to have controlled the leakage. The valve cover gaskets may have sealed with this product. I will update.
The other problem was an on-going coolant leak probably from a warped upper plenum intake. I had previously replaced the radiator and flushed the coolant system very well about a year prior.
After much research, I used 5 Bar's leak radiator stop tablets. They are the same material that GM used. They are mainly crushed walnuts, and very finely granulated. I cannot believe that it actually worked. After what I have researched, the golden seal powder or the Bar's Leak tablets are the ONLY material that should be used in the coolant system.
Fortunately, I may not have to take this engine apart to replace parts and seals. I have done the work installing an intercooler on my GTX, but I have huge misgivings with the electrical wiring problems I have had. I do not want another electrical nightmare....hope this helps others..cheers KEV

Glad when old threads come with a follow-on....well this one is not that old...
..my '93 now has developped a very slow coolant leak at the front of the intake manifold...enough to notice it, not enough to make an issue ....will see how it develops....eventually will look for these stop tablets...

Well the leak at the throttle body heat circ are of the upper plenum came back.

I followed JRS3800 advice and got fel pro intake gaskets, dorman upper plenum, and new hose for the inlet to the lower intake.

Definitely a demanding job. Changed out the lower intake manifold, and installed new thermostat and new sender for the temp gauge.

The intake gaskets were very damgaed and the nylon 66 material was very degraded at the coolant passages. Totally collapsed from the DEX COOL.
The lower manifold was changed by Pontiac a long time ago due to corrosion. I should have asked GM to pay the bill.