DocLee

Okay so I am curious about an issue I'm having with my coolant and particularly the reservoir. I can fill up the radiator and the reservoir with coolant, less than a week can go by and the reservoir is empty and the radiator still has some in it, but not full. It is somehow disappearing during driving because there are no puddles or even drops under the truck before or after driving. I noticed that it has one of the cheap plastic GM radiators in it if that helps with diagnosis. Any help is greatly appreciated.

P.S. The temp gauge never goes above the normal level and never shows any indication of overheating no matter how far the distance I travel, highway or city driving.

GranVille-4crawler

You should list your engine and truck. I have no idea what engine your running but here is a link I dug up with the handy "search" button. hope it helps!
https://www.yotatech.com/forums/f116...coolant-94180/

bryan89

sounds like you may have a small leak in your head gasket to me...

i have seen trucks with head gasket problems that leak water only into the combustion chamber and its burnt off. it would never leak into the oil galleries.

if its a bad enough leak it will be visible in the oil as a milky sludge. but since it takes a week or so to go down, i would say its pretty small leak, if it is one.

the only way to tell for sure is to test it.
you can buy the kit and dye from the common auto parts warehouses. it basically uses a chemical to test whether or not trace amounts of combustion gases are present in the coolant.

if you get a positive test, you can tear it down and verify your findings by looking at the state of the pistons. a piston that has been seeing water will be clean in shiny looking (or at least cleaner than the rest), where as one that has not will still be charred and crusty black looking.

DocLee

Sorry, forgot to mention my specs. I've got a '95 4x4 extended cab with the 22RE. Thanks for the find and the advice. Hope it isn't the head gasket.

4Crawler

iTrader: (3)

You might want to have the cooling system pressure tested and/or have the coolant tested for exhaust gas contamination (NAPA sells a test kit for that). I had such a situation on my '85 where exhaust gas would over pressure the cooling system (a gauge would show the pressure rising with engine revs), blow out the cap into the overflow tank as you were driving. Would not happen with the engine stopped or at slower speeds. One time I did catch it driving up a long steep grade and I could smell the coolant and pulled over and saw the overflow full and overflowing. Gauge only moved slightly higher than normal (maybe one needle width) as long as there was some coolant in the rad.

But a pressure test will also show if you have a high pressure leak that only happens when the coolant is hot and under pressure. In that case, the hot coolant will leak out and vaporize and you won't see any drips or signs of a leak.

DocLee

Okay so I filled up the radiator and reservoir again. When I filled up the radiator I found one half of a round rubber gasket floating in the radiator and I was able to snag it out. Any ideas where this gasket might have came from and gotten into my radiator and wouldn't this probably be the cause of my missing fluid if I could find where this busted gasket came from?

TOY89

Hmm gasket? Could it be the rubber gasket on your radiator cap?

gwat

Cant rad fluid get into the block once the timing chain has wirn through.....?

Team420

Bingo!! I had the same symptoms with my truck for a while... couldn't figure out where the coolant was going, but DID pull a small round rubber gasket out of the top of the radiator, I looked at the rad cap, and it appeared fine, but.... sure enough...new rad cap fixed my mysterious disappearing coolant