Northstar Engines and System Technical Discussion Discussion, 1999 northstar warped heads in Cadillac Engine Technical Discussion; I had two occasions of overheated coolant and stopped the engine and let it cool. In both cases I was ...
I had two occasions of overheated coolant and stopped the engine and let it cool. In both cases I was able to restart and the first time I got about 1500 miles before it happened again. This time I went about 5 miles to a repair shop.
It had been experiencing coolant loss prior to these episodes and the same repair shop had no success finding the cause of the coolant loss. Pressure tests were fine, they said. Also there was no stains showing coolant or oil leaking in the drive way.
This time, the same thing, they couldn't find anything and I told them to do a compression test and check the codes. The compression test was ok. They found an oil leak around the oil pressure gauge and replaced it. Upon further testing they found that the pressure cap was faulty and replaced it. They took it out for a test drive and it overheated. Now they tell me the heads are "cracked" and will need to be repaired. The guy states that putting in the new pressure cap caused an increase in pressure such that it caused an increase in the size of the leak to a very large leak. He also stated that the compression test would not have found the bad heads.
Automobile(s): White Diamond '03 DHS (with DTS floor shift)
Re: 1999 northstar warped heads
Cracked heads are almost never heard of. A "compression test" would not show a bad head gasket, but a "cylinder pressure test" would. Any decent mechanic should know the difference. How does he know that the head is cracked. Have they been removed and inspected?