1993 four runner overheats when driving uphill

chairman,

I would look into the thermostat. You will have to pull it out and put it in a pan of water on the stove and heat it up to and make sure that it will open all the way. If it does the you might have to do a compression check to see if you have low compression on any of the cylinders, mainly at the #6 cylinder, this is assuming that you have the 3.0L v-6.

thank you again. i will check it out tom. and it would be great if it were the thermostat. fingers crossed

chairman said:

my 1993 toyota four runner runs great. my only problem is the temperature gauge stays about in the middle almost all the time with the exception of when i go up a reasonably steep incline. the engine then heats up to the red in less than an 1/4 of a mile. as i crest the hill and start down the hill it cools reaasonably quick as long as i keep the idle up. the radiator is brand new and the coolant is not leaking out. it only overheats when going up an incline. thanks to all.

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What was the reason for the radiator replacement?

Do you have AC? When the rad was replaced was the front and grill checked and clean for debris, fluff, etc? IE) Infront of the AC Condenser.

Did you check to see if there is oil in your coolant, or coolant in your oil.

A leak down test is much better than a compression test. A leak down test will let you know if your headgasket is leaking by pressurizing the system with compressed air. It will also let you know how much you are loosing in pressure, etc. It is possible you may have the beginings of a headgasket leak.

It is possible, but not likely that the thermostat is the issue. If they go, they normally break in the stuck open position.

Did you replace your rad cap when you replaced the radiator? Did you burp/bleed the system for air?

i purchased the car 3 weeks ago so i don't know why the rad was replaced. i will check for debris. there is no oil in water or vice versa. thank you so much for the help.

chairman said:

i purchased the car 3 weeks ago so i don't know why the rad was replaced. i will check for debris. there is no oil in water or vice versa. thank you so much for the help.

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Ok, fair enough. LOL.

The debris will be like drier lint on the screen. At normal driving it is fine, but when any extra or prolonged energy is exerted she will not cool as quickly.

The debris will be in front of the AC cooling fans or in front of the condenser core.

I doubt the radiator has debris stuck to the front of it as it is a brand new rad.

Let me know how you make out.

will do first thing in the morning. thanks again.

chairman said:

will do first thing in the morning. thanks again.

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How did you make out?

On the cheap side: Check your fan clutch. If dirty or has grease on the front, clean the thermal spring with parts cleaner. If the fan clutch is bad, replace with new. Also, if you have an electric fan for the a/c condenser, make sure it works too.
I also agree to look closely for possible head gasket failure. It may be the end result of the last over heating that required the new radiator. Call the prior owner, hopefully he will be straight up and tell you about the last over heating incident so you can figure where else to look.