coolant loss

[dima4855]

91 Montero, 3.0, Automatic, 118000 miles.

Experiencing loss of coolant through resevoir overflow tube, only during highway driving (is fine at idle).

Things I have done:

Idle test for 1 hour with A/C on, no overheating or coolant loss.

Changed thermostat, radiator cap.

Backflushed cooling system.

No visible leaks on water pump, hoses or radiator.

Tested radiator by warming-up vehicle and feeling around the radiator to make sure that it was evenly hot. It was not until we revved-up the engine to 3000 rpms.

Has anyone else had this problem or know what could be causing it?

Thanks!

[dima4855]

Anybody out there??

[usacanadiangirl]

I have a 95 montero LS and have just recently noticed that I'm losing coolant. I don't know how or why, just that it's disappearing. My montero has always had a problem w/ burning the oil and using the oil but that's about it. Now, I noticed this problem w/ the coolant. I am also smelling some kind of exhaust or something - don't know if it's related or not.

So I am no help to you b/c I don't know what's going on - but just wanted to let you know that I'm having a similar problem.

Have you had any insight as to what's going on since writing?

[dima4855]

It has something to do with the pressure being excessive in the coolant system, or it could be a bad radiator, thermostat stuck closed. Something is creating the pressure. One mechanic seems to think that I have a bad head gasket and exhaust gases are going in the coolant system. I find that very hard to believe.

[usacanadiangirl]

good luck figuring out the prob - hope you get it fixed - if you do, maybe you'd post a quick reply as to what the prob was. I'm looking to sell mine now so I'll just let the buyer know what's going on -