Ok, I'm not exactly sure how to describe all this, but I'll give it a shot:
1991 Montero, freshly rebuilt 3.0/auto. Runs like a champ, but has now developed some strange behavior with the cooling system. Was driving home and the temp gauge started climbing way out of its normal condition. It did not overheat before I got home.

Opened the hood for a visual and the coolant overflow bottle is bubbling like crazy and spewing out everywhere. Hmmmm. After it cooled down, I checked the level and it was almost a half gallon low. I topped it off, sealed things up, and no more issues, until about a day later, the same thing. Temp is rising, overflow is puking, coolant is low.

This time I checked the radiator immediately after shutting it off and I'm finding cold spots. I got bit by this in my Raider. Ordered a Chinese aluminum radiator(yeah, yeah, I know), swapped it out, changed the cap, and now I'm thinking I've got it all fixed. Wrong!

A couple days go by and I've got temp problems again. This time, coolant is leaking out of hoses that were never leaking previously. Checking the coolant level and again, I'm down about a half gallon each time. I've re-tightened the hose clamps, but then it starts puking out the overflow again.

This morning I do my check/add water routine and as soon as I vent the cap, the bottom tank of the radiator is leaking. This is with the engine cold and obviously no pressure on the system, since the cap is off. Anytime I shut the engine off, I do a quick underhood/under car check and if the overflow isn't overflowing, I don't see any coolant on the ground. If it's going into the engine, it must like running on anti-freeze as there's been no exhaust steam or cylinders mis-firing.

Two more weird things:
1) I have intermittent heat inside. Earlier in the week, I had pulled over to take a phone call(engine still running). I had plenty of heat when I stopped, but as the temperature started to climb, the air from the heater got colder, and then no heat at all as the temp climbed higher. When I drove off, the temp came down and the heat back on.
2) When I open the radiator cap to refill, it smells like exhaust. I am thinking this is not a good thing at all. Seems to me the only thing that could cause this is a cracked head, but the machine shop checked them out and said all was well. I've watched for bubbles with the cap off and the engine running, but I don't see anything unusual.

Any ideas what's causing all this strange behavior? It's certainly not making much sense to me at all. I'm wide open for ideas/suggestions. Thanks!

Go buy a combustion products in the coolant test kit at the auto parts. Lisle makes one. I think you have a head gasket leak or a cracked head.

Funny gauge movement is air pockets masking the gauge sender from liquid coolant. You also have symptoms of excessive radiator pressure.

Sorry....

Ditto.... Sorry, but I would go back to the rebuilder & talk to them.

Ed

Head gasket issue.

Combustion gasses are being forced into the cooling system forcing the coolant out.

When the heat was good, that was when your coolant was full, and as it started to push the coolant out, it overheated, and the heater core was not getting coolant flow from the hot engine(because there was no coolant flowing) and stopped blowing hot.

Head gaskets, and or head rebuild is in your future.

Frank was really determined in trying to let everybody know that the headbolts have to be checked with a rebuild.

They bottom out early and then the wrong torque is applied to the head. This can causes combustion to enter the coolant system and cause pressure and heat.

Thanks for the input, everyone. This Montero has been the project from Hell. See my earlier posts on the transmission debacle. I have another set of heads left over from the original engine. I guess it would be prudent of me to send them off and then pick a weekend to swap out. I don't mind working on my stuff, but when I have to things over again, it really takes the fun out of it. Again, many thanks!

Good plan. Make sure you (a) clean out the threads in the head bolt holes in the block with a bottoming tap (make your own by whiz wheeling the taper off a normal hdw. store tap - use a wet rag to prevent overheating the HSS tap)and use a new set of head bolts, and measure the bottomed out length of the head bolts in the block holes (start of bottoming resistance, not dead jammed down) from the bottom of the bolt head to the block deck = A. Measure the head thickness from the top of the head bolt boss to the block gasket surface. Add .040 for head gasket crushed thickness (est.) and the thickness of the head bolt washer to the head thickness = B. B must be greater than A or you bottom the head bolt before you get clamping force on the head gasket with the head.

Dadgum - I'm pleased as punch to see the advice finally catching on as a fact! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Frank

To add insult to injury, the aforementioned Montero never made it home last night; at least not without help from the tow truck.

Topped off the coolant before leaving work and while on the freeway, the temp gauge started climbing. As it approached 3/4, it started pinging terribly and started losing power. I got it to the next off ramp and it died before I even got to the end of the ramp(but managed to get it safely out of traffic). It smelled VERY hot.

I walked to the nearest gas station with my 2 gallon jugs. The truck had cooled down considerably by the time I got back. It took both gallons and still wouldn't top off. Then I see water dripping from the drain hole in front of the muffler. Not good.

I tried to crank it over. It acts like it has zero compression and water was shooting out the radiator filler. Guess I have a new project....again. In the meantime, I've pressed my Raider back into service until I can get the other one straightened out.

More details when I get the Montero disassembled.

I've got no advice to offer, just sorry to hear about this and feeling your pain <img src="/forums/images/graemlins/frown.gif" alt="" />

Eric W.