Running hot, please help

Its a 95 tacoma four wheel drive, four cylinder. It has new water pump, thermostat, radiator cap and had the cooling sytem flushed. Did a compression check and all four cylinders hit 150 and didnt bleed off in 15 min a peice. funny thing is It takes the truck about 45 min to start getting hot, I can drive it around town, back and forth to the store and such and it never runs over half way, but when I start to work I drive an hour and about 45 min into the drive it gets hot all of a sudden, and thats just in the day time, when im coming home it never gets hot. And i mean it gets hot like have to pull over cuz its headed for the red, but under half way on the way home. I know its cooler at night but as hot as it gets in the day I would think it would still get at least warm at night.

Anyways im confused and wondering if anybody had any ideas before i tear into the motor to check gasket,block and head.

 

rad plugged up?

 

X2. I'm with Chris4x4 on the fan clutch. You can also add a fan without a clutch (one brand is FlexFan) that helps a lot. Just runs full speed all the time. Fan clutches often will lose up to 10% per 10k miles. Try spinning the fan while the engine is off (obviously) and cold. If it is at all easy to spin, it's a bad fan clutch and could definitely cause you to get too hot. A very common problem that is often overlooked.

 

I may be wrong here, but any head gasket leak would cause radiator overflow and milky radiator fluid... Right? Anybody confirm that?

 

this too, or you can get a flex-a-lite kit. electric motor running off of an adjustable thermostat. will also free up some horsepower... clutch fans are pretty power hungry.

 

If you are on the highway, it's more than likely your radiator. Fan clutch would be more evident driving around town. Are you loosing coolant? I had a headgasket leaking on a 22r I had. It ran fine but used coolant. Would only overheat if I let it get low.

 

Fan is good and complete colling sytem has been flushed, and water is flowing well thru radiator. Havent noticed low coolant but once it ges hot it looses it, and exhaust has a slight antifreeze smell to it, but no oil in water or water in oil.

 

oh and thanks for the fan ideas but i want to fix a problem and not cover it up with extra cooling fans, Because there is something def wrong for it to all of a sudden hit the red.

 

Did you change the thermostat before or after this problem started? I have recieved defective thermostats from the parts store before.

 

I put two new ones in it, still same prob.

 

Another thing you can try is start the truck up completely cold, drive around the block and check for pressure in the top radiator hose. On my old 22r, the headgasket was leaking enough to pressurize the cooling system. It's normal for pressure to build while warming up the engine, but around the block a time or two should not result in full cooling system pressure when the engine is stone cold.

If you are suspicious of the headgasket you can buy a chemical block test kit at NAPA. It will tell you if there are combustion gases leaking into the coolant.

Do you still have the original radiator? Are the fins blocked with bugs or mud? I would still be suspicious of the radiator if it's never been replaced. You might be able to see coolant flow, but that does not mean all the tubes are clear. Can you see any deposits around the tubes inside the radiator?

 

the fan isnt masking the problem. The fan is vital for cooling the truck.

Can you drive on the highway or maintain 45mph without overheating?
If so there is a problem with the fan. If not there is a flow issue. not enough flow due to rad block or possibly an air bubble in the system. water pumps dont pump air and many cars have to be "burped"

Does running with the heat on help? if so, once again fan or rad block.

Try another new tstat. I had a bad one and bought one from advanced that was fine until i installed it. i opened it up to double check because id still overheat and it was stuck shut.

Head gasket can still be bad. They dont always have to become compromised between water jacket and cylinder, they can also leak into the oil passage so check oil for water.

Edit: Head gaskets are easy on 4 bangers so it might not be a bad thing to try if youve already replaced the tstat and pump

 

could be an intake leak

 

A family member of mine just took a road trip in their jeep (i know). The jeep had been running fine in 90 degree weather around town. When they hit 105 degree weather, they had to drop speed to 55mph and run the heater full blast to keep the temp out of the red. The radiator turned out to be plugged up internally. It ran fine all the way home in the same weather with AC on.

 

like intake manifold gasket? I was thinking that too because its pretty common on chevys. I wasnt sure if the intake manifold gasket had a water jacket through it like a chevy v8

 

I can run it at 70-75 or about 45 min, then all of a sudden you better find a place to pull over, Its so consistant that the last three times it did it at the same place and i pulled over at the same spot, but like i said 70-75 all the way home at night and never over half way.

 

Not sure about the 4cyl, but I know my v6 does. Had it happen before. If the exhaust smells like coolant then I'd smell the radiator for exhaust. I know a compression leak will over pressurize the radiator and cause overheating pushing the water out. I had it happen on my v6, no water in the oil just compression going into my cooling system. Wasnt a good deal at all.

 

It seems to have alot of pressure. When its hot you can pop the radiator cap and it will drop instantly to half way and spew pressure out for a while. Then the top radiator hose will jump like its getting burst of air.
And yes its the stock radiator with over 200,000 on it.