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Engine over heating

My engine has been over heating very quickly when I go down the highway. I have checked the thermostat and have pulled the water pump out and it seems fine, I mean the shaft turns and the impeller turns. i put the thermostat in a pot of water and slowly brought the temp up and watched it open and used a temp sensor to see when it opened and that was about 185 degrees. I put all new antifreeze back in it and the is no fluid leaking into the crank case. The timing belt does squeal at startup sometimes.

the year of the car is 1998 and it has 225,000 miles

You went through the trouble of inspecting the water pump and you did not replace it?

A subie can overheat if the timing belt is off by a tooth. Did you replace the idler tensioner? At that mileage, I would have replaced the belt, thermostat, pump, tensioner, seals, etc. You’re there anyway.

Now that it was allowed to overheat, the head could have warped and/or the headgasket could now be hosed. Hate to suggest that but do tread lightly. You don’t want to do damage.

Also, a blocked up radiator will cause this.

Yup, it sure can. I do hope he’s being careful as a mouse because Subies don’t take kindly to overheating, as we all know.

O K and thanks for the great feedback. I’m thinking I new a different motor, I did get it hot on New Years weekend so I have probably got a warped head and or engine case. I just don’t understand why it is not putting out white smoke or steam through the exhaust if coolant is going through a cylinder.

As for replacing parts, the water pump is 3 years old and I put a new timing belt on last year.

What are the thoughts about the timing belt tensioner being weak and it slipping on the water pump pulley, it has squealed a few times.

Well, no one has mentioned the cooling fan/s . are they working??

If it was the cooling fans it would overheat at low speeds and idle. You don’t even need the fans at highway speeds.