89 350 Sub Intake Manifold Coolant Leak - Again

I've removed the intake manifold on my 89 Suburban 5.7L, 96k mi, to try and fix a coolant leak. Coolant is disappearing from the cooling system and showing up in the oil (about 1qt/3000mi).
Last year I changed the intake manifold gasket for similar reasons. At that time it was leaking coolant out the top manifold on the right front part of engine. The gasket replacement fixed that leak. I used a FelPro gasket along with permatex Hylomar HPF sealant. I used the Permatex goop to hold the gasket in place while I installed the intake manifold. The permatex was worthless in that regard. The gaskets were not perfectly flat. They would lift and slip out of place before I could get the manifold on. Instead I used a drill bit through the bolt holes to position the gasket once I had the manifold in place. I'm wondering if the Hylomar sealant prevented the gaskets from sealing properly? They sure were easy to remove.
I probably was leaking coolant into the oil before the first repair. I din't pay attention because as I was losing coolant, I could see it appearing on top of the engine (no, it was not leaking from the thermostat. It was definitely from the intake manifold/head gasket.)
What do y'all recommend for holding the gaskets in place during manifold positioning? Something that will _positively_ seal around the coolant passages. Or should I install the FelPro gaskets dry? Both the heads and manifold are clean and dry so the gaskets should stck fine, if that's how they're designed to work. Or should I go with a different brand?
I was going to take out the plugs in the bottom of the manifold and reseal them. They are in _tight_! There was no sign of leakage around them so I left them alone.
Everything is all cleaned up and ready to reassemble. I could find no obvious sign of leakage when I took the manifold off. It's kinda hard to tell though since some coolant spills out when the manifold is popped loose. 1qt or two qts every 3k miles (~ 100 hours) is a pretty slow leak, but it's enough to thin the oil. Oil pressure dropped quite a bit between changes (from 20psi to 10 psi at idle). If this manifold gasket replacement doesn't fix it I'll try some stop-leak. I'm crossing my fingers the leak isn't deeper down in the motor.
-RC
R.Clarke spam snipped-for-privacy@BlocKmindspring.com RTP, NC, USA
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Make SURE the heads and intake are flat first, it doesn't take much warpage to cause problems. Use a straightedge on the flanges and see if you see any light or space under it. Normally gaskets are installed dry or with just a dab of silicone in a noncritical area. For ones that refuse to stay put use Hi-Tack gasket cement. LocTite # 30526 Spray a THIN coat on the gasket and stick it to the CLEAN head. Put the intake on and bolt it down IN sequence. DO NOT tighten each bolt/stud in one step. Tighten them in stages.
Steve W.
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wrote: Steve wrote:

The bolts were tightened in order and many stages last time. Gaskets had the Permatex hylomar goop on them, which I'm _hoping_ was the problem. Thanks for the quick reply.
At least the old gaskets were easy to remove.
-RC
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On Sun, 17 Jul 2005 18:23:10 -0400, "Steve W." wrote:

I've got some warpage. The left side of the intake manifold is flat (<.0015"). The right side is out .002-.004" depending how you look at it. I can fit a .004" feeler gauge under the end of the straightedge if I push the straightedge down on the opposite end.
The cylinder heads appear to be flat.
The original leak occurred on the right side of the manifold so that agrees with the measured warpage. No idea if the warpage is distributed evenly between the front and rear of the manifold (.002" of gap at each end) or if it's biased toward one end (.004" of gap at one end only).
How much slop can the gaskets accomadate?
-RC
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R Clarke wrote:

My 95 K1500 350 needed the gaskets replaced 2 years ago ~ 190,000 miles. I used Fel Pro gaskets dry with a small amount of black Permatex RTV only at the 4 angled points where the block meets the heads. Now at 250,000 miles with no leaks.
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R Clarke wrote:

    Gasket Glues/Aheasives/Sealers I use: 1. Black RTV 2. Gasket Shellach 3. 3M Super Weather Strip Adheasive 4. High-Tack
    Black RTV on any irrgular oil sealing surface, execpt fuel pump or timing cover. I always do Small Block Intake Endrails with RTV. Do not use the rubber end rails provided in kits. Most instructions even tell you this.
    Gasket Shellach (Permitex Indian Head for example), I use on timing cover gaskets, water pump & fuel pump gaskets. Brush it on lightly, apply the gasket. Align the gasket and allow to set for a few minutes. Next apply a light coating to the mating surface, and install cover, or pump. The stuff also works well on carburator bowl gaskets.
    3M Super Weather Strip Aheasive also lists on the tube "Gasket Adheasive". It's yellow in color, and often refered to as yellow snot. For Intake gaskets apply a thin bead around the ports on the cylinder heads, hold gasket in place for a minute. If gasket is problematic, install intake bolts, and hold pressure on the gasket untill adheasive sets. After you have one side done, do the next. Allow to set for 20 minutes before applying RTV to end rails.
    High-Tack is a adheasive & sealer in a aerisol can. Normially red in color. Great for cork gaskets, and paper/felt gaskets. Apply a coating to mating surface & to gasket. Allow 15 minutes before applying gasket (like with contact cements). Appling a coating to the other surface, or cover is optional.
    Most Fel-Pro intake gaskets are marked Top or Up on the side to face the intake. High rail heads will have a crowned gasket that crowns up towards the intake before installation. Trying to hold them in place with a regular sealant will not work. You need to either put them in dry, or use a adheasive, or adheasive&sealant. Yet one strong enough to hold the gasket flat to the ports. Charles
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