I'm thinking I have big problems. I seem to be losing alot of coolant but I cant find a coolant leak. Just an oil leak. Is it time for a new head gasket or is the Arizona heat the factor? <img src="/forums/images/graemlins/scared.gif" alt="" />

The coolant has to be going somewhere. Have you checked the oil to see if it looks milky?

The oil doesn't appear milky and I don't see any white smoke coming out the exhaust. Is there a common area that coolant leaks start at and evaporate? Are there hoses behind the block that carry coolant? The Montero hasn't over heated yet. YET

You dont run your heater much in AZ huh? Get in your rig and drive it around with the heater on and see if you smell antifreeze......if you do, your heater core is leaking.

I'll have to check that out later. Its over 100 degrees out now. Thanks, I will past back later this evening and let you know.

Yup heater core, heater core inner or outer hoses, or from the water pump into the valley between the heads and down either side of the tranny.

My old 76 Jeep Wagoneer had a leaky heater core for a while. I was in Idaho during the winter (-20 on occasion) though so I had the heater cranked all the time. There was absolutely no mistaking the smell.....sickly sweet. <img src="/forums/images/graemlins/barf.gif" alt="" />

Put the defrosters on after the truck heats up and see if it fogs up the window. <img src="/forums/images/graemlins/kewl.gif" alt="" />

same thing happened to me and it was the heater core hoses. It would only leak when the presure was up and since it was a pinhole, it would evaporate on the engine. I finally found it when the hole got much bigger I could not tell by looking at the hose on the truck. take them off and inspect.

There are lots of places to inspect. Check the easy stuff first. A slow leak out of the thermostat housing or upper radiator hose can evaporate almost as fast as it leaks causing you to lose coolant at the same time making it hard to detect. Also check the the the small hoses behind the engine that go into the fire wall and all their connections.
Checking the heater core is good advice. But also..

Look for coolant drip around the the transmission bell housing. This could mean a bad water pump o-ring in the back of the pump. Also the water pump itself can have a slow leak from the shaft seals or housing seals that will evaporate before it will drip out in some cases. Also the tube that goes to the back of the pump can corrode and cause problems, again look for the drip on the back of the engine...Good luck.

im loosing coolent also. it can either be ur heater core. pump or many other things. if its ur pump. its gonna be a ***** to fix. put sore radiator stop leak in it and see what happens. if u still noticing leakage then u need to tear apart the front end and check it out