blazer from hell epsode 27 - crack or gasket?

[NINFan]

as many of you know, i've replaced just about everything except the frame on this devil's spawn. now i have a new problem. it's using coolant. a LOT of coolant. it's in the crankcase and coming out the exhaust. oil also smells of fuel. i heard that these engines are notorious for intake manifold gaskets. problem is, if it's really a crack or head gasket, i'm not sure i really want to bother. i'll just drive it off a cliff and put us both out of our misery.

anyone have any thoughts about how i can definitively determine if it's a crack somewhere or just the intake gaskets?

thanks.

[old_master]

Most likely the lower intake manifold gasket. Felpro has a new design called "perma dry plus", Part No. MS98002T and it WORKS! When you take the lower intake off, look closely at the gasket around the coolant ports, you'll see the problem. If you don't have the Felpro gasket in there, its either leaking, or it will shortly, guaranteed!

[4x4 blazerguy]

If you have spent that kind of money fixing everything but the frame you might as well fix the leak.

[NINFan]

Originally Posted by 4x4 blazerguy

If you have spent that kind of money fixing everything but the frame you might as well fix the leak.

not if it's a crack in the block, dude.

[NINFan]

worst fear realized -
got the thing all put back together and it's still burning water. looks like it's from 1 cylinder. now i'm stuck. i want to trade it in for the cash for clunkers program, but it means i have to do the head gaskets, and i STILL won't know if it's a crack somewhere.
uggggggghhhhhh

[MT-2500]

If you have to pull the heads taske them to a machine shop aand have them checked for cracks.

[NINFan]

ya, thanks. i'm on that one. problem is it still won't tell me if there's a crack in the block. But there's a new clue. dipstick smells like gas, so i think it can't be a crack in the block. only way for gas to get into the oil would either be a crack in the head or the head gaskets.

[old_master]

A rich fuel condition is the most common way for fuel to get into the oil. It seeps past the rings and into the crankcase. A cracked head or bad head gasket will not cause fuel to get into the oil.

[NINFan]

Originally Posted by old_master

A cracked head or bad head gasket will not cause fuel to get into the oil.

why can't fuel mixture get into an oil channel by blowing past a break in the head gasket?
besides, the thing that's worrying me the most is that there's still water in the oil, so i'm concerned that it could be a crack in the block at the water jacket.

[old_master]

Intake passages do not go through the head gasket.

It is possible for a coolant passage in the head gasket to leak into the galley. Coolant is under pressure and the galley should have a slight vacuum form the PCV system.

Fuel mixture travels through the intake manifold and past the intake gasket into the combustion chamber. This path is under negative pressure, (vacuum). If anything, a leaking intake gasket around an intake runner will suck oil from the galley into the combustion chamber.

A leaking intake gasket around a coolant port will leak coolant into the galley.

Faulty head gaskets are not a known issue with the 4.3L. Pressure test each cylinder with compressed air. Connect a pressure guage to the cooling system. If cooling system pressure rises, you know which cylinder to start looking for a leak in. If you have fuel in the oil, look for a leak in the fuel delivery system.

[NINFan]

Originally Posted by old_master

Intake passages do not go through the head gasket.

d'oh

Originally Posted by old_master

Faulty head gaskets are not a known issue with the 4.3L.

ya, but that was before some idiot (me) mixed glycol coolant with the dexcool. you should have seen the intake manifold gaskets. completely destroyed. guess you shouldn't do that to a 10 yr old car with 150K on it...

[old_master]

Is coolant still getting into the oil?

Did you use the Felpro "perma dry plus" MS98002T gasket set?

Were the coolant ports on the heads and intake manifold pitted from corrosion?

[NINFan]

yes, coolant (water) and gas still in crankcase. you can smell gas in the radiator, too. The lower intake gaskets were completely destroyed, but no real damage to the manifold ports themselves, other than the normal rust around the water ports. The surfaces of the heads were flat and very clean once i cleaned them up. I can't believe i could have screwed up installation of the manifold gaskets.
I used Felpro gaskets, but i'll have to check on the part number.

[NINFan]

WAIT! i have a new theory. i didn't replace the upper manifold gasket. if that were bad, couldn't that allow gas into the galley? I've never taken one of those things off, so i don't know if coolant passes through there or not. still wondering how i could be getting so much coolant in the oil without a crack somewhere.

[old_master]

The upper intake gasket seals vacuum in the plenum only, sorry.

Engine oil, coolant, and transmission fluid all pass through the radiator. If the oil cooler leaks inside the radiator, you'll see oil in the coolant AND coolant in the oil. That might be something to check.