Why am I overheating?

[Midwestmonsta262]

Hey guys, I just recently replaced the motor in my 87 MC SS. Only to find
Out that I have an overheating problem. The radiator seems to be fine....when
The car runs hot and I turn it off it sounds like the coolant is boiling at a very
High temp. When I am able to get the cap off the coolant geysers out of the radiator.
Is it the fan? Water pump? Hoses? Cap? Couple people told me it could be head gasket
But I find that hard to believe since I just replaced a new rebuilt motor. There's not even
50 miles on it yet. Any suggestions? Thanks.

 

[565bbchevy]

I have a few questions:
Did it run hot with the previous engine?
Do you have a temp. gauge and if so what was it reading?
You replaced what I would guess would be a 305 what did you install in it's place.
Is it using a stock or aftermarket fan set up?
Give as much info as you can on what was changed and what was not.
I could be a stuck thermostat, faulty water pump or fan.

 

[Midwestmonsta262]

Yes it was over heating before this motor got put in. I went from a 305 to a 350. Stock everything besides
Radiator.

 

[Midwestmonsta262]

New thermostat as well. Hoses are original. Temp gauge varies.
Sometimes it takes longer for it to overheat than other times.

 

[565bbchevy]

New thermostat as well. Hoses are original. Temp gauge varies.
Sometimes it takes longer for it to overheat than other times.

Usually an overheating issue you would want to be resolved before installing a new engine and typically you also install new hoses at this time, hopefully you have not damaged your new engine yet.

A few more questions:
What happened to the 305 did you overheat that or blow a head gasket?
Temp gauge varies? Give some numbers for how hot it is getting.
What radiator did you put in?
Do you have a fan shroud?
Did you install a new radiator cap?
What driving situations makes it run hot the soonest?

 

[Midwestmonsta262]

I don't think I've had it running enough for me to damage the new engine.
The original 305 was garbage. I dropped in a diff 350 and that one had
A cracked head. Radiator is a 3 core with new cap. There is still a shroud
With factory fan clutch and blade. It gets the warmest when it is in idle. The hottest
I've had it was probably 210 degrees. Am scared to run any hotter.
But when I shut it off it geysers.

 

[pontiacgp]

210º is not overheating. The coolant isn't boiling over, you have air being pumped into the coolant. I would shut it down and have a talk with the engine builder or whoever you bought the engine from. It either has a cracked head or a bad head gasket

 

[bill]

210º is not overheating. The coolant isn't boiling over, you have air being pumped into the coolant. I would shut it down and have a talk with the engine builder or whoever you bought the engine from. It either has a cracked head or a bad head gasket

Bingo ^^

 

[Midwestmonsta262]

I can hear it bubbling and boiling. Or is that air?

 

[bill]

I can hear it bubbling and boiling. Or is that air?

Are you using a proper mix of coolant or just water? Like PontiacGP said, its most likely air being introduced into the system from the head/head gasket, which creates more pressure than the system is designed for and it has to go somewhere, usually in the overflow tank. Good luck...