hey guys a while back I was posting about issues I was having with my series II pulling all the timing at WOT and it has been getting slightly worse. The other day I punched it and the motor cut off and slowly came back online. Low speed there were no issues only under WOT acceleration. Well I left work the other day and the Fiero had left an antifreeze deposit on the ground about 3ft in diameter on the muffler side. I was confused as there is no coolant lines on this side of the motor so I started it up and reved her up a bit and saw coolant coming from the lower intake gasket! Apparently this was a problem with these motors. If shes leaking on the outside than I bet she is leaking into the combustion chambers. I began tearing into it then I also found that the reusable TB gasket from ZZP was leaking coolant into the SC as the inside was covered in antifreeze.

I hope this was the cause of my stumbling issues!

Replacing the gaskets from the LIM up on swap 3800s are always a good thing to do even if they are older motors with lower miles. The gaskets have been improved upon over the years by GM and recalls have been done. I used the garlock gaskets from ZZP one time and while they worked I really didn't care for them. I use the stock gaskets now and always use a thin coat of black RTV on both sides. This leak is probally your issue as when you get on it there is more pressure in the coolant line causing it to leak more coolant into the LIM. I had a leak similar to this but it was on a coolant filler neck I made that had a pin hole in the weld. Would only leak when doing high speed runs and the coolant would burn off before I could see where it was coming from as I could only smell it.

Use the latest GM p/n for lower intake gaskets: 89017825. They should be metal shim gaskets with impregnated sealing material. Don't forget to order the two little yellow o-rings that seal the lower intake to the bottom of the SC. You also should replace the gasket on that little coolant bypass cover that bolts onto the lower intake under the throttle body while you have the intake off -- these do tend to leak over time. You do NOT need to put RTV on them other than in the areas where the heads meet the block (where the intake gasket meets the valley end seals).

Clean the old gasket, sealer, and deposits from the cylinder heads using a razor blade, gasket scraper, and chemical cleaners only. Lay some lint-free towels in the lifter valley to capture any debris you scrape off. Don't be afraid to get out the shop vac and vacuum out the lifter valley after you are done cleaning (just make sure you don't suck up any chemical cleaners as most are flammable and the vacuum motor can ignite the fumes).

DO NOT use a die-grinder mounted surfacing pad to clean the cylinder head gasket surfaces as this can throw finite metal particles into the lifter valley which can get into the oil and trash the bearings. Use gasket scrapers / razor blades ONLY. If there is significant pitting on the surfaces of your cylinder heads where the gasket seals around the coolant passages, you may need to remove the heads to have these resurfaced to correct the condition and give you a good seal.

Follow factory assembly, tightening sequence, and torque specifications during reinstallation of the intake manifold, throttle body, and supercharger.

-ryan

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6+ years on this same swap -- NO engine or transmission failures...

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

[This message has been edited by Darth Fiero (edited 02-19-2010).]

Thanks for the input guys. Hopefully this will solve my running problems.