3.4L with coolant in oil. Is it Intake gasket again ?

[Cressidaadr]

I have been working through a few cosmetic items and decided to pull an oil sample to send in even though it looked just fine from a visual inspection. (Note to others - you cannot always see the antifreeze in your oil - my oil, oil level, dipstick, and cap all look normal.) You know it isn't good when the oil lab calls and tells you to dump your oil now because it is loaded with antifreeze.

Here is their report summary and this is with about 3k miles on the oil:

copper 25 -Silicon 20 -iron 79 -Sodium- 452
chrom---2 -Potassium 1032 -alum--11 -lead------26
Oil Visc 10.23 -Nitration 29

This van has 135k miles and has complete records and maintainance history since new. The original intake manifold gaskets were replaced at 36k miles by the dealer. Then again at 86k miles by independant garage (using the "new redesigned" GM gaskets set) and now it looks like it will be time to do the job again. Is 50k miles all one can get with the GM manifold gaskets ?

Dexcool antifreeze had been changed and the level kept full over the years but I will switch to something else now - probably Zerex G05 as I do not feel like trusting Dexcool any more. Likewise will go with Felpro gaskets this time around.

However I do not want to get ahead of myself so I am now trying to nail down just how the coolant is leaking into the engine oil. I did a pressure test of the cooling system and it repeatedly drops from 15 lbs back to about 7 lbs within minute or two. It will not hold pressure above the 7 lbs at all.

Doesn't that basically confirm another intake manifold gasket leak so can I rule out a problem with the head gaskets?

I will try and do the repairs myself (my first time) unless it something beyond the intake manifold gaskets.

The van runs fine with no engine issues other than this antifreeze leak and even though the wear metal numbers are high I hope they will come back down once I get the coolant out of the oil.

[cjstew4]

Switch to the green antifreeze this time and make sure you get that water pump and t-stat changed out this time along with the heads resurfaced. Not that any of those would have necessarily caused your problem, but just get really stressed when there is a cooling problem. My waterpump leaked bad a month after my IMG and head resurfacing repair. Although they say that "Deathcool" if changed regularly will be just fine, it is not fine with me. No warranty with DEATHCOOL. They don't have to pay for IMG repairs, just watch that orange cr.....p do it damage over time. Don't however ever have anyone one do a coolant flush that can compromise all sorts of seals as well as start leaks that weren't there before. Applies to the tranny flush as well. Keep us posted on how it turns out so that we can all learn.
My 97's IMG and head repair with switching to green coolant is still going strong now at 172k after being done at 95k mi.

[MagicRat]

That fast pressure leak down is bad news. Put the system under pressure and take a GOOD look around. Make sure its not a hidden leak, such as the heater core etc, before you do the repair.

I agree to use the green stuff and change it every 2 years, tops. The Dexcool is essential for certain GM all-aluminum engines like the Northstar which cannot tolerate the silicates in the green stuff, but I'm pretty sure your engine can.

Also, if/when you do the gasket, add about 3 coolant tablets from GM. Place them in the lower radiator hose before you put it on. Do not add them to the overflow tank.
This is a stop-leak additive that for years GM added to all aluminum engines for many years. It will seal up any tiny leak you may get before it gets bigger.

[Cressidaadr]

Originally Posted by MagicRat

That fast pressure leak down is bad news. Put the system under pressure and take a GOOD look around. Make sure its not a hidden leak, such as the heater core etc, before you do the repair.

Also, if/when you do the gasket, add about 3 coolant tablets from GM. Place them in the lower radiator hose before you put it on. Do not add them to the overflow tank.
This is a stop-leak additive that for years GM added to all aluminum engines for many years. It will seal up any tiny leak you may get before it gets bigger.

The leak is internal as nothing is showing up. The news just got worse as I am seeing a steady stream of bubbles appearing in the overflow tank now. Before I didn't see any bubbles and the it was because the fluid level was too low in the reserve tank. It is the darn head gasket. I was going to do the IMG myself but I just don't know if I am up for head gaskets as I may be getting over my head. The exhaust manifolds fasteners scare me as I know some will break off but I guess a machine shop can clean them up when they check out the heads

[wafrederick]

GM does put in junk exhaust manifold studs in to the cylinder heads on the 3100 and 3400s.You can drill them out very easily and use a straight flute easy out.I hate the spiral easy outs,grips on the broken fastener too much and the broken fastner does not come out.It depends if it got too far,I have seen some that drove them with the intake gasket leaking and ruins the bottom end.Bearings and antifreeze do not mix,antifreeze eats them up.Felpro does have the upgraded intake gaskets for the 3400,made out of metal and are more money than the plastic one.Dorman products does too including new intake bolts and cheaper than Felpro.