QuestionI have a 96 deville 4.6l northstar. I replaced the heater core, radiator, all hoses, water pump and thermostat and new coolant. It is still running hot. Temp get up to 250deg and I can hear the coolant boiling in the expansion tank. Can you please tell me what the problem is and what is the normal operating temp?
AnswerHello,
My concern is your statement "still over heating," which makes me wonder if you would be able to fix an overheating problem on a guess by replacing parts. First, when the engines over heat the first thing that happens as a result, not the cause is the head gaskets blow.
These things have so many issues that I don't know where to start. Cooling fans not coming on? Excess gasket material stuck in the under size cooling jackets? Broken fins on a water pump.
If you had this aluminum engine to 250 degrees, I would almost bet head gaskets are gone or block is cracked in a cylinder wall.
To illustrate what happens to these engines, if you had a camp fire and threw an aluminum can in it, you would find out real quickly as to how well aluminum holds up to heat. Picture that can being your engine.
These engines simply cannot be run that hot without doing major damage.
Worse yet, any used engine in a junk yard will be in the same condition.
You need to run a radiator pressure test and check for leaks and it would be a true miracle if the head gaskets were not blown just from running at 250 degrees and as I stated, the is only the effect.
I have seen as little as a piece of old thermostat gasket or water pump gasket cut of coolant circulation, and in that case, the only thing you can do is have the cooling system flushed and hope whatever it is comes out.
I am concerned as well as all the components you have changed. The only reason the heater core would be changed is coolant would be leaking on the passenger floor, because with the air on, the heater core is bypassed any way. I wonder as to why the radiator was changed if the car had a heater core problem. Everyone thinks to change the thermostat on these Cadillac engines that are running hot, with almost always the same results-the thermostat was fine and not the problem.
You can't be driving the car with temps like this, because the engine components are literally melting!
I guess the first thing to do is go back to the very beginning before the parts were changed. Was there any engine work dealing with the cooling system before it started over heating? Did you confirm the fans came on when the engine reached operating temperature? Was the radiator cap checked? If you don't have proper pressure, the coolant will not circulate. Yes, you replaced the radiator, but you said nothing about the cap.
You have stuck a lot of time and money in this car and I hope its not in vain.
Let me know your situation after considering all this.
http://www.autotheftexpert.com
