I have a 1985 Military Chevy Blazer with a 6.2 diesel engine. Cooling system won't pressurize. I pressure checked the system and it held pressure for half an hour but won't hold pressure when I'm driving. Radiator cap has been replaced. Any ideas?
If it won't hold pressure, there has to be a leak somewhere. Those diesels will a lot of times start to blow head gaskets. So the first thing you'd want to do is watch my video "how to tell if your head gasket is blown" and you can do that test to see if your head gasket is blown for yourself. If you don't want to do that, then a technician from YourMechanic can come and do a head gasket test at your home or office.
See if your head gasket is starting to blow; it's a very common thing. If it won't pressurize and it has a leak anywhere else, then when you pour the water on it, it's going to pour all over the ground and you are going to see where it is coming from. If it doesn't, the odds are your head gasket has blown. This is not to mention that the car is 31 years old, which makes it more prone to failure due to its age.
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