garyfisherz0

First of all I know there have already been a number of threads on coolant leaks for this truck but I haven't seen any with my same scenario.

I have a 97 Tahoe 5.7 it has been losing coolant for close to a year with no sign that I could tell of where it was going, last week I finely noticed a visible leak it is clearly leaking on the back corner where the head and block meet on the driver side just above the oil filter and unless it has figured out a way to defy gravity it can't possibly be coming from the intake manifold. It only leaks when the engine is running there is no oil/coolant mixing. I can take the radiator cap off with the engine running with no geyser affect from exhaust gases leaking in the cooling system and the vehicle has never overheated I can clearly see that the temp gauge is working (when I first start it the needle is on cold and over time it will rise but never above normal operating temp)
I was planning on doing a full gasket change I.E head intake manifold valve cover to the fel-pro gaskets. My question is since the vehicle has never overheated the whole time I have had it (9 years) and the coolant mystery leak started about a year ago would it be necessary to have the head’s machined before reinstalling them?

cleveland63b

You should atleast check them anytime you remove them

Whiskey_Sauer

I didn't get a slow leak. Mine just popped out a chunk of gasket and I lost 80% of the coolant in under 15 seconds.

garyfisherz0

So check them as in pressure test, and check for any warping?

garyfisherz0

mine's not losing fluid that fast before I noticed the spots on the ground I was maybe adding 1/4 gal every month or so, of course in the back of my mind I was wondering where it was going, but once I noticed the spots and located them as coming from the head I quit driving it, now I'm just waiting for some time off so I do it.

Sledgehammer

Same with mine. Small leak and nowhere visible. Then one day driving slowly it all came out instantly..... . SOld it. Now same issue on my new tahoe (99) ugh

warf1955

3 years ago I had the same problem, could not figure out where coolant was going. This went on for 3 months,so I talked with my mechanic. We figured it out. The coolant was going out the exhaust, when we pulled the head we also fount out that the vortec was blown. So I had to replace it also, that meant I had 2 problems not just the one. I had waited to long to replace the head gaskets. This may be the problem with yours also. This is on a 1997 Tahoe 5.7 L vortec engine. I hope this may be a little help for you.

garyfisherz0

Thanks for the info I hope it don't end up being too much trouble I have most of the parts now Just waiting on the Head Gasket set, that should be here Thursday my local Advanced Auto Parts store didn't have the one I wanted in stock so I got it through them online. I have read that a lot of people have had trouble with the TTY head bolts that these aluminum head motors use breaking when installing them any advice out there on this?

garyfisherz0

The fun continues, I've been real busy and have only had small time slots I could spend working on it, I've got most of it torn down now, when draining the fluids I did notice there was a very small amount of Antifreeze in the oil, but not a speck of oil in the antifreeze. The exhaust manifolds where a real pain getting off, at least none of the bolts going into the head snapped off which I hear is common, the flange bolts were the real trouble, ended up just cutting them off. the a/c compressor bracket was a pain getting that moved out of the way too, I think Chevy was kind of dumb the way they designed that, there are bolts and nuts hidden on the bottom side of it that you would never expect would be part of the same bracket, and of course the Chiltons manual doesn't have a thing on the A/C system, I ended up googling it and was able to find some info in it. I've got the whole day Friday this week planned to get the rest of it tore down, all that is left is the distributor, valve covers, intake then heads. I'll try to keep posted on how it turns out.

garyfisherz0

All went well the intake and heads are off, the stupid water line quick connect broke off in the intake manifold, I was able to get the rest of it out though with out to much trouble. I'm hoping to bring the heads into the machine shop tomorrow. then while they are being checked out I plan to get all the gasket surfaces cleaned up good and ready so when I get the heads back I can get right at putting it back together.