Phantom Water Leak

[landmine]

Hey guys need some help here. I've got a 2004 GMC Sierra with a 5.3. I'm losing water at about a gallon every month and a half to two months. Checked all the usually suspects and everything is dry. I'm out of ideas. Before anyone ask it's got the 862 heads not the castech 706. By the way it has 97k on it.

[r1byker]

What have you checked? Is your oil level okay?

[pm26]

You probably have a very small leak in the radiator or the coolant overflow bottle. Check for any signs of powder deposits on the surfaces of radiator and bottle, which would indicate coolant leak.

 

I had a similar problem with my '99 Mazda 626. I was losing coolant at the rate of about 1 quart/100 miles, and could not find the leak. Finally, I noticed some small coolant droplets on the plastic radiator upper hose neck. I wiped those off and did not see any cracks or pores in the neck. After driving for a while, the droplets appeared again. It turns out that there were microscopic cracks in the neck causing the coolant to leak, but at such slow rate that it most of it evaporated before it dripped.

Replacing the radiator cured the problem for good.

[landmine]

Yes the oil level is fine. Doesn't burn or leak any. I've checked the water pump, the heater hoses, the heater core, the radiator hoses, the radiator, and the over flow. No signs anywhere.

[kal el]

check the gaskets from the bottom looking up. This is a common problem, the leak usually only happens when the truck is running and warm, so as it leaks out it gets burned off. good luck I have seen this many times.

[landmine]

which gaskets are you talking about. and yes it does only leak when running.

[jblakeney]

Water Pump mounting gaskets.... I hunted a leak in my truck from October 2001 till about 3 years ago......... I FINALLY GOT IT..... Passengers side gasket the rubber had broke loose from the aluminum gasket....... Common problem 20+yr GM Tech told me what the problem was without opening the hood.... Leaks when the truck is running and the system has pressure.... Let it sit long enough to cool down to feel water dripping from the gasket and the block is DRY as can be....... Crank it and it will leak when warm...

 

Not saying that's your problem but sure cleared mine up and I have now fixed a couple for friends with the same issue.

 

Jbo

 

EDIT: PULL THE TRANSMISSION DIP STICK ALSO........ I have had several that the internal transmission cooler in the radiator bust and begins mixing (ALL GM's tooo even my 2001 3/4 ton did it)... Usually sucks antifreeze into the transmission........ Quite rapidly.... If your over full...... GET A NEW radiator and flush the transmission with 16 or so quarts of fluid..

[K20and2500HD]

yep what jblakeney said, water pump gasket the rubber and metal will separate when hot, Also dexcool burns or evaporates into a white looking stain hard to diagnose.

[jro909]

check the bunghole on the waterpump, seen a few 4.8s that had a leaky bung hold(ha ha sounds dirty) and the coolant would either hit the ground or evap before it was noticed

[doverarjim]

My leak turned out to be a head gasket but I found it to late!!!

[landmine]

Thanks guys, I'll check the water pump gaskets today. Hope it isn't the radiator or head gasket tho.

[BigSilver]

Hey guys need some help here. I've got a 2004 GMC Sierra with a 5.3. I'm losing water at about a gallon every month and a half to two months. Checked all the usually suspects and everything is dry. I'm out of ideas. Before anyone ask it's got the 862 heads not the castech 706. By the way it has 97k on it.

Consider trying out Steel Seal product. I just saw it on Scotty Kilmer's video. The manufacturer has its own videos.

 

The product makeup is not disclosed, though I'd guess it contains sodium silicate as an actif.