Luck has run out on '99 5.7L

Whatever you do, don't just go into some shop telling them that you need head gaskets. I can tell you the ratio of intake gasket replacements to head gasket replacements on that engine in our shop.......5000 to 1....maybe!

It's most likely to be the intake gasket. Along with the coolant leaks on that engine, the intake gasket is also known to warp around the cylinder head ports. Often, it is bad enough to cause a vacuum leak at the port. You get a nice miss that is virtually impossible to detect by the old "spray" method along the exterior of the intake manifold to cylinder head parting line.

Ian

Ian,

Thanks for the reply. The odd thing is that there are coolant trails down both forward sides of the block and down the sides of the oil pan. I could see one head gasket weeping, but both simultaneously seems incredible! It runs great, never overheats, but does have the cylinder 4 misfire, more often these days, when on strain that settles down once you get off the gas. Could some coolant be getting into #4 or a vacuum leak on the intake at #4 cause this misfire code?

I do plan on taking a very close look this weekend, before taking into a shop, to see if there is an indication of a trail from the intake manifold all the way down..

Kev>

This actually occured to my 96 Tahoe with the 5.7 just a couple of weeks ago. It was leaking on the front and back, 2 different gaskets. There had been a slow leak previously, but something caused them to pop and antifreeze was flowing out like a hose.

Brandonb

You can't get coolant into the cylinders on these engines due to a leaking intake gasket. The coolant ports and cylinder ports are too far apart for that to happen, plus they are side by side, so gravity will dictate that the coolant either leaks outside (down the front of the engine, or over the rear of the bell housing...sometimes the coolant will follow the parting line of the cyl head to block, which can fool you into thinking that the head gasket is leaking) or inside, straight into the lifter gallery and down into the oil pan.

It's usually very hard to see the front parting line of the cyl head/intake from the front. You can just see the drivers side, but the passenger side is blocked by the alternator bracket. Another common place for the coolant to appear is the starter area, passenger side rear. Also...you can take the oil filler cap off, check and see if you can detect either a creamy looking substance or beads of what appear to be moisture. Taste it....(just a little...don't want you keeling over from the chems)...if its sweet, it's coolant in the oil.

Ian

Check out the Chevy Tahoe page. You might be able to find out some information at that site. It's