Chevrolet Repair: chev venture temp problem, head gasket leak, coolant leaks

Question
I own a 2001 chev venture 130,000km. 1 year ago the temp gauge would fluctuate sporadically (high then low then normal etc). There was visible sludge in rad so were advised to have a rad flush to replace the dex cool coolantwhich has a bad history of gumming up. This fixed the problem immediately. Now, one year later, same problem. I just had a pressure test done and showed no leaks anywhere,the cooling fans cycled fine, and the coolant looked good as well. While the tests were performed the temp gauge showed no signs of a problem. I will just have to keep driving and keep an eye on temp till it shows up again and get worse. do u suspect it being a sticky thermostat or can there be a head gasket leak without showing up on a pressure test? im hoping the problem is sporadic and dissapears on its own, but if it shows up again, would u suggest replacing thermostat?
thanks for your help.
Todd

Answer
Hi Todd, I'm sure that this engine has a coolant leak...either the rear head gasket or the intake manifold gasket which can also leak into the engine oil and not show a leak. Some coolant leaks are very small and don't appear on a pressure test. I look for traces where the coolant has been and leaves a trail of orange.

Hope this helps

Have a Nice Day               Mark