Questioni did a pressure check and it was good ,put new thremostat, when car is idle its at 196-203 but when i tested it out and gave it gas to get on the higway it overheated at 235-245 and i shut it off to cool, i got no white smoke , and clean oil too, i relif pressure on the cap and water came out the overflow hose ,what is my problem
AnswerHi George,
Well, I don't like guessing on these because of all the problems these engine have, but will give you ideas of what I have run across over the years with the Cadillac cooling systems issues: Water pump, radiator, radiator cap not holding pressure (you might have tested that already), cooling fan not working, rust restricting the cooling system flow.
You did not state the thermostat you put in, but you might have put in a 160 or 180 degree instead of the 195.
These aluminum engines were notorious for over heating problems and at the high temps you are referring to, they do self destruct! You may have been lucky not to pop those head gaskets yet, but you will running that hot!
I think the next thing to do is a cooling system flush and check to be sure the cooling fan is operating, yet at high speed it shouldn't have to, unless the radiator is plugged or the impeller blades are broken on the water pump (have run across this more than once).
All I can do is give you thoughts from my experience and cannot give you an absolute answer. There are just too many different things that create overheating on these engines.
If you are in fact running it at 235-245, I am surprised that you have an engine left. Aluminum heads will warp or crack, head gaskets will blow, the aluminum engine block can crack.
As for your testing the pressure of the system, that is good and checking the oil, that is good. Watching for white smoke coming out of the exhaust, that is good too.
As I said though,if you are running at those temperatures, with an aluminum Cadillac engine, it has the same effect on the engine as Russian roulette would have on a brain when the bullet comes out.
The bigger problem: If the engine is destroyed, chances of you finding an engine in the junk yard that is any good is very near 0!
Replacement with a new engine from GM will run you $4-$5K.
Try getting the system flushed and check the fan. Easy to check--turn the ignition on and put the A/C on max (car does not have to be running) fan should come on momentarily. If not, you have a problem with the fan or the relay.
If you are still having over heating, you will need to decide what to do-change the water pump or put a radiator in. If it were my car, I would go for the water pump because the radiator should be good from the flush. You may find the water pump has failed. All you need is problems in one impeller blade.
You did not mention how this problem came about. Was it all of a sudden with no warning? Was the temp gauge gradually getting warmer after time?
