I Cannot figure this out!

kolenich · June 25, 2003

Hi everyone,

I have a 90 GMC Suburban 1500 5.7L 4x4.

With the temp in Ohio in the 90s my suburban has started overheating.

Last week I found the cooland Low and replaced the Thermostat and it was fine till today when it started overheating and trying to stall again.

I checked the cooland and it was about 2 1/2 gallons low again. I filled it and it ran fine. So the question is where is the coolant going. I have checked heater core, water pump radiator, overflow tank, head gasket, and radiator cap off the list and hear is why.

There is no water in the oil or out the tailpipe.

Everything in the engine is very dry!!

No smell or interior coolant.

No leaks under truck.

I am at a loss. Does anyone have any ideas.

thanks for reading

Karl

Jersey Tahoe LT · June 25, 2003

Do you smell coolant at all? It could be the intake manifold gasket. I have a slight leak and it is most likely comming from there. No signs of leaks what so ever. That is all I can give you. Good luck.

Later,

Brandon

MarkD · June 25, 2003

Cracked head/head gasket would pressurize the cooling system and blow your coolant out of the overflow tank. It would have to run for a little while, might not happen sitting in driveway.

I had this happen on a '84 Honda CRX. I could drive about 12 miles before all of the water was forced out of the overflow.

Boat Gears · June 25, 2003

A blown head gasket, on the inside would allow coolant to be sucked into the cylinder and burned off.

Also, look for bubles in the coolant with the engine running, that can indicate a blown head gasket.

WEFs99 · June 25, 2003

Intake manifold gasket.

kolenich · June 25, 2003

Thanks for the replies. It sounds as though it is probably the intake or mabey the head gasket. But what I dont understand is where is it going. Shouldnt I be able to see it burn out the tailpipe or see coolant in the oil? I also checked for bubbles in the coolant when it was running and didnt see any.

karl

varmint2506 · June 25, 2003

Sounds like a head gasket either pushing it out or pulling it in and burning it off. I had the same symptoms on my '89 for some time. I kept adding coolant and couldn't find where it was going. The head gasket finally let go and I filled a cylinder with coolant. Found the leak, the hard way.

Good luck.

MoJo · June 26, 2003

If it is a head gasket, it will cause a 'miss'. If it is missing and is a head gasket, pull the plugs. Any cyl. that is getting water in it will have clean spark plugs, the others will have carbon build-up.

Also, I've had the intake leak and it doesn't drop that quickly. Maybe a qt a week.

Remember, hot coolant evaporates quickly, so it's hard to 'catch it in the act'.

Finally, the best way to find out the answer is a good radiator shop that can pressure test the rad. and also check for exhaust gas in the coolant.

Lots of luck.