MtnToys

85 4runner with a 22re. The engine is not the original. The radiator was replaced at some point by the previous owner with 3core for a 22ret. I replaced the water pump and thermostat about 1000 miles ago.

Recently it has been overheating. About a half gallon of coolant is blown out of the overflow. The temp slowly rises until it overheats. I think it's over heating because of the lack of coolant. I don't think the lack of coolant is due to the overheating. I let the truck cool down and I'm able to refill the radiator. Then the truck runs normal for about 50miles or so before the cycle repeats itself.

I replaced the radiator cap thinking that the old one was not holding enough pressure allowing the coolant to blow by. I still have the problem. The only other thing I can think of is that the head gasket is going. Exhaust gasses could be pressurizing the cooling system and blowing the coolant out? I smelled inside the radiator and it definitely doesn't smell right (smelled the radiator on a buddies 85 and 91 pickups to compare). I have no signs of water on the oil dipstick, no white smoke, the truck runs normal until it looses enough coolant to overheat.

I'm going to try replacing the thermostat tomorrow in hopes that it's something simple and not the head gasket. Thanks for any help.

dcg9381

[QUOTE=MtnToys;50560012]Exhaust gasses could be pressurizing the cooling system and blowing the coolant out?QUOTE]


Bingo. Might check the plugs to see if one or more is discolored.
If you can see piston tops, one may be more clean that the others...

MtnToys

What color would the plug be if coolant was leaking in? I doubt there is much if any coolant leaking into the engine as I have no smoke.

I mixed two different kinds of coolants when refilling the radiator. Could they have reacted to cause the funky smell? Both of them said they were compatible with any other coolant. I know you?re not supposed to mix coolants, but I was in a bind and I figured it wouldn't really matter since its all blowing out anyway. I have to drive home (300 miles) on Saturday and I'm mostly just hoping this is something easy to fix.
Any other ideas? Thanks.

mt_goat

I think I'd try a pressure test on the cooling system. Good luck

maxpower_hd

I doubt you had a reaction if they were compatible. My 1st guess would be the Tstat sticking. Replace the TStat and see what happens.

kcrunner

I was having the same problem with mine. I replaced the thermostat, pressure tested the cooling system, did every possible thing I could think of, still overheated.

Blew the head gasket and (coincidentally) timing chain at once. Took the head off, had it pressure tested, and it was cracked in FOUR places. So, that was my problem. Probably not the same problem, but certainly the same symptom.