2002 Mistubishi montero sport is overheating.

I just bought a 2002 montero sport with the 3.5L. I drove it for a couple days and it was getting hot like hot hot steam and what not. I took the thermostat out like I did in my mighty max and it is still overheating. My mighty has a cracked coolant reserve. This thing has a crack in it too but not as bad. Tried the same remedies on this thing but no luck. I drained the coolant out ran water through it drained it out put new coolant 50/50 ran it till it was hot and drained it again. Still no luck. Also there is kinda a gray sludge in the radiator as well. Any ideas. Thanks!!!!

The grey sludge is a possible indicator of oil making it into the cooling system. You can try filling it with distilled water and adding dishwashing detergent to it, leave the cap off with the heater on and run it hot to break up the oil sludge, flush, rinse, repeat. The oil sludge retains some of the heat and can clog heater and radiator cores. If you are getting continuous contamination in the system you have a problem (a blown head gasket or something more sinister like a cracked head) Replace the cracked reserve tank asap as it will ambush you.

I didn't notice any coolant coming out of the exhaust like it did when I blew my head gaskets in my mighty. But it does seem weird

There are different signs of a blown head gasket or cracked head. Lots of steam/white smoke from the exhaust, oil in the coolant, coolant in the oil or weird bubbling in the radiator (exhaust gas bypassing into the cooling system)

Check the radiator. Remove the cap and insert a fine rod or stout wire into the accessible core passages. If the wire doesn’t reach the bottom tank, the passages are plugged and the radiator needs to be rodded out or replaced. You can also run it until it’s hot, shut it off, then feel the radiator core. If the radiator is plugged, the center will be cooler than the outer sides. According to the radiator shop that rodded out my rad, the passages with the greatest air flow plug up first.

I've wondered about this - what would happen if you had the above situation of clogged cores and artificially heated them with a heat gun? Could it cause the calcification/debris to break up? :scratchheadyellow:

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Originally Posted by geezer101

I've wondered about this - what would happen if you had the above situation of clogged cores and artificially heated them with a heat gun? Could it cause the calcification/debris to break up? :scratchheadyellow:

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I’ve never heard of using just heat. Some deposits produced from aluminum corrosion are very hard and would take a lot of heat to break down. You could combine a strong solvent with the heat gun effectively hot tanking the targeted area. But if you don’t remove one or both tanks, you’d only be able to know you’ve opened the passages accessible via the rad cap. Clearing the other passages would be guesswork.

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Originally Posted by Jsuydam1

I just bought a 2002 montero sport with the 3.5L. I drove it for a couple days and it was getting hot like hot hot steam and what not. I took the thermostat out like I did in my mighty max and it is still overheating. My mighty has a cracked coolant reserve. This thing has a crack in it too but not as bad. Tried the same remedies on this thing but no luck. I drained the coolant out ran water through it drained it out put new coolant 50/50 ran it till it was hot and drained it again. Still no luck. Also there is kinda a gray sludge in the radiator as well. Any ideas. Thanks!!!!

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..... edit , pictures vanished.

I would start by doing a combustion gas leak test on the radiator. https://www.amazon.com/Lisle-75500-C...0220526&sr=8-2
This is the one I use, reasonably priced and works well.
I think you're ultimately going to be looking at a head gasket or cracked head/block. Sludge in the coolant is usually brown from iron oxidizing as the coolant's corrosion inhibitors wear out. I suspect the grey sludge is a head gasket repair in a can. There's a decent chance someone dumped a can in and sold the truck immediately there after.
The combustion gas leak tester will save a lot of time poking and prodding around trying to figure out what the culprit is. If you can see bubbles in the radiator cap shortly after starting before the coolant has warmed up, you can pretty much guarantee it's a head gasket or crack.

*something I observed recently. I cobbled together a replacement radiator for my Gen 1 and decided to repaint it myself with satin black epoxy paint. After hitting this thing with paint stripper, not all of the paint wanted to budge after pressure cleaning it so I tried a heat gun. Wasn't entirely successful but I could hear a lot of 'pinging' while I was carefully heating up the cores (mostly in the central ones) The heat did actually break up some of the scale build up and a lot of flakes fell out of the outlet/inlet pipes.

I didn't take into consideration someone may have done a shade tree fix on your engine and used a stop leak treatment on it. This crap is nasty to get out of an engine and radiator...