Where is the coolant going?

[toynbyu]

My 1997 FJ80 is going through coolant at a very rapid rate, about a gallon every two hours on the highway.

I had it pressure tested, it sat at 13lbs for 20 minutes= NO LEAKS

No puddles under the truck.

I replaced the radiator cap, filled the reservoir went for a 45 min drive and got home to a empty reservoir.

Any ideas?

Thank you.
Mike

 

[Paul_L]

PHH, rear heater hoses, radiator, head gasket are possibilities.

 

[scottryana]

A gallon every two hours is a major leak. If it is being burnt off you should be able to smell it, or see smoke, if its leaking somewhere get under the truck with a flashlight and a mirror and you will see it. Do you have spots on your driveway when you park?

 

[toynbyu]

That is what is so frustrating. No spots in the garage. Passed the pressure test. I don't know what more to do.
There has to be a explanation.

 

[lilevo]

It can pass a pressure test just fine and still be the head gasket.

 

[elhombre]

Are you sure it was completely full when you went on this last trip. You may have fixed it with a new cap but now need to get it completely topped off.

 

[js93cruiser]

You need to do a cylinder leak down test...

 

[lilevo]

Leak down test still won't necessarily show any head gasket or coolant leaking issues.

It will just show the condition of the valves/rings.

What he really needs to do is stick a boroscope down the spark plug holes. A clean shiny piston will tell you which cylinder the HG is blown in.

 

[js93cruiser]

Leak down test still won't necessarily show any head gasket or coolant leaking issues.

It will just show the condition of the valves/rings.

What he really needs to do is stick a boroscope down the spark plug holes. A clean shiny piston will tell you which cylinder the HG is blown in.

Yes it will, i do it on a daily basis to check for hg leaks, you put a funnel on where the radiator cap goes and fill it partially with water, set the particular cylinder to tdc, start flowin the air and if it has a leak bubbles will start coming out of the funnel... Easy

 

[lilevo]

Well I say "won't necessarily" because the OP will probably do it with a negative result.

If he's losing that much coolant a borescope takes a whole 5 minutes and the result will be fairly obvious and easy.

 

[CJF]

Leak down test still won't necessarily show any head gasket or coolant leaking issues.

 

[toynbyu]

THANK YOU to all. Back to the shop on Tuesday....

 

[Youngjoonni]

THANK YOU to all. Back to the shop on Tuesday....

Red flag for me. Back to shop? Was it in for a repair that wasn't disclosed earlier?

 

[Paul_L]

I was having similar symptoms, Just replaced my PHH. Monitoring the coolant. I should know in a few days if that was the problem.

https://forum.ih8mud.com/80-series-tech/767747-another-coolant-loss-thread.html