94 SR5 Mountaineer

I've noticed on two occasions that my truck overheats while going up hills while the rpms are low for an extended period. Only when these two conditions are together though. The hill was maybe a quarter mile long, and it was on a rough rural road. I was in first gear and towards the top I noticed the temp gauge getting close to the red. Long story short I got to the top, checked my reservoir (full), let the truck cool off and kept on going and it was fine.

The only thing I can think of here is that my water pump might need replaced soon, because when I pulled out to the main road and got the rpms back up, it went back to normal without any problems. That tells me it wasn't circulating enough at the low rpms. I was also thinking I would flush my radiator and refill with Toyota red coolant and add some Water Wetter for good measure.

I should also add that my radiator and thermostat were replaced about 10k miles ago.

JasonYota

iTrader: (1)

Your lugging the engine plus going up hill. Your not turning the engine over fast enough for the water pump to circulate coolant through your radiator. Also at lower RPM's your clutch fan probably isn't turning fast enough to pull enough air through the radiator.

94 SR5 Mountaineer

Makes sense. I knew it had to be a circulation problem, but wasn't sure if this was a normal problem to have or if it meant there was a weak point in my cooling system.

RSR

Especially this time of year, it shouldn't be overheating on a 1/4 mile hill in first... Definitely continue to troubleshoot through/before summer.

Start w/ flush and go from there... Might plan to replace your radiator. The champion cooling CC50 is supposed to be one of the best options for our trucks.

94 SR5 Mountaineer

Update: even though everything looked full on level ground, I parked the truck uphill and let it run with the radiator cap off and heat on, and it took in about a quart more. So hopefully I've displaced all the air. All seems to be good now.

MaK92-4RnR

fan clutch.

RSR

Fan clutch is definitely worth checking. And would make alot of sense.

You're 5 speed, so you have no tranny heat bleed into coolant, so can't be that.

Also make sure you're running the 180* 3vze and not the 190* 22re thermostat. (Shouldn't cause the issue you're having but worth double checking.)

Also check your coolant antifreeze temp with one of those things with balls in it in the auto store. Possible I suppose you have a freeze clog somewhere in your radiator that's stopping coolant flow too. Unlikely, but possible considering how cold you've had in the Ohio Valley region recently...