I just purchased a '92 Montero SR with 168k on the clock. The truck is solid, passed emissions with no problem and overall seemed healthy. The truck was slow to warm up, so I decided to replace the thermostat today. This apparently set off some chain of events that I cannot explain.

As soon as I refilled the coolant and started the engine, I had a smoke/steam combo coming out of the exhaust. There was a puddle of water forming below the exhaust tip. I also noted a reduction in oil pressure. The smoke/steam was pretty bad. I also noted the presence of coolant in the valleys near the fuel injectors on the passenger side. It was not coming from the thermostat housing.

I drove the car around and the smoke/steam seems to have subsided, but the coolant leak persists. I am showing very little oil pressure at idle. Oil level is good and doesn't look milky yet.

Any ideas of what is going on?

I purchased my 90 knowing that it had blown head gasket.It would start and run fine for about two minutes then the steam would cloud out of tailpipe sweet smelling stuff.You should be able to remove spark plugs the really clean ones will be where coolant is getting in.You may have had an accumulation of stop leak at t state that was freed up and created a blockage elsewhere....like a passage in a head.GL its a pita...I got out of it for around $400 for head kit and machineing heads. 008 warp on passenger head..also bought new head bolts and shorten them if heads are machined.

I pulled all 6 plugs. None of them looked steam cleaned. Here is what one of the plugs looked like.

http://sr20de.homestead.com/files/carpictures/IMG_20110108_165639.jpg

So I started the truck cold again and the same process repeated. When its cold I get steam/water out the exhaust.....which starts to subside as the engine warms up.

I still have coolant pooling near the fuel injectors on the passenger side.

Is there any way for coolant to be getting burned without any indicator on the plugs?

Head crack into the exhaust port, maybe, but the leak in the valley leads to believe something more like a leaking valley pipe, water pump oring, or perhaps a leak at the throttle body, which is water heated, I believe.

Your plug looks normal coolant will clean them up right away in my experience.As far as water coming from exhausted coolant has a very sweet smell,and would probably become worse as engine warmed.And yes there is a 5/8 -3/4" tube with an o ring that may be suspect in that area.Heater hoses on back of engine.And coolant lines running through throttle body possibley a bad gasket there would allow some coolant into combustion chamber.tech section stickied on this forum should have some good line drawings of these external coolant lines.

Also check water bypass hose off upper rad hose connection. I'd stop driving it until you get this figured out. Not sure if this is relevant but thermostat needs to installed at certain angle. I'd also try to inspect cavity under intake for coolant where the water pipe to the runs into the rear of the water pump. Taste the water coming from tailpipe for sweetness.

Thanks for all the tips guys! When I installed the new thermostat, I just matched the orientation to the old one (though it may have been incorrect as well.) What would the symptoms be of an incorrect clocking on the thermostat?

We've got snow in Denver today, so I won't be able to look at it till later. I'll post back with what I find.