Engine running hot

[Blue68Coupe]

So my 289 started running hot all of a sudden. I know it's been hot here but the temp gauge never moved near half let alone 3/4. I have a high flow 180 degree thermostat. I tested it on the stove and it opened right where it was suppose to.

So I took off the radiator cap and ran the engine. I did not see the radiator empty when it opened. Actually I noticed when I rev the engine the flow increases inside the radiator. That tells me is open but It tested fine.

The engine is newly rebuilt but the radiator is original. I am wondering if the radiator is not cooling it enough so the thermostat never gets cool enough coolant to close. I am leaning toward replacing the radiator.

Anyone have any thoughts on it?

[Gearhead999]

You could just replace it or take it out and send it to a local radiator shop and have them check it for restriction.

[88ponyboy3]

Originally Posted by Blue68Coupe

So my 289 started running hot all of a sudden. I know it's been hot here but the temp gauge never moved near half let alone 3/4. I have a high flow 180 degree thermostat. I tested it on the stove and it opened right where it was suppose to.

So I took off the radiator cap and ran the engine. I did not see the radiator empty when it opened. Actually I noticed when I rev the engine the flow increases inside the radiator. That tells me is open but It tested fine.

The engine is newly rebuilt but the radiator is original. I am wondering if the radiator is not cooling it enough so the thermostat never gets cool enough coolant to close. I am leaning toward replacing the radiator.

Anyone have any thoughts on it?

fan clutch is bad i would say, start the car and watch the fan spin and then shut the engine off and watch the fan, it should not spin around after the engine is turned off but a few times

[Blue68Coupe]

Thanks but no clutch fan but I did convert to a variable fan from the old X fan.

[Phillyfanfrombirth]

Well, one suggestion would be to get a temp gauge that has a numerical readout... that would give you a more definitive read on what is happening.

Does it heat up just while idling/sitting in traffic or is it a problem even when you are driving?

It's a rebuilt engine... any chance that you have a set of underdrive pulleys on it?

Have you tried turning on the heater when the temp is rising? Does it blow hot air? Does it change the water temp?

Is it blowing water out of the radiator cap? Any puddles? The hotter the water gets, the more the pressure will be...

Did you flush the radiator when you had the motor rebuilt? If you did, how bad did the water that you were draining look?

[rwhite65]

If you havent had the Radiator cleaned out, do so and give yourself a good baseline. Couldn't hurt any especially since you have a new rebuild.