Cars are constantly evolving and so are the test procedures and the problems that go with those evolving cars.  One of the more common things that we see these days: overheating, or continuous loss of coolant.  How do you go about testing that? Well, it’s pretty simple.  First thing that you check of course is the thermostat, you want to make sure that the thermostat is opening at the proper temperature; you’ll need a service manual to know how to do that correctly.

Then of course you’ll want to check the radiator cap.  A lot of overheating problems are nothing more than a bad radiator cap.  Here is where you use a radiator pressure tester: you put the radiator cap onto an adaptor, the adaptor onto a pressure tester, and you test it, takes all of ten seconds, then you know whether the radiator cap is good or bad.  If its bad: replace it.  And also, if you want to be pro-active, put a new radiator cap on your car every two years and you’ll avoid a lot of hassles.

But there are other things that happen to cars that aren’t as straight forward.  That pressure test that’s often used to check for the condition of the cooling system itself and to check for head gaskets is not a positive test by any stretch of the imagination, because most of the things that it’s going to find you could find with the naked eye just by looking for droplets of coolant. One of these problems here, the real biggy, is a bad gasket and you say, “well, but I’m not getting any steam out of the tailpipe, and I’m not getting any coolant in the oil, and I’m not getting any oil into the radiator, couldn’t be a head a gasket!”

Well, yes it could!  Because in early stage failure what happens is that you get exhaust gas into the coolant.  How do you go about finding that?  You use a liquid like block tester liquid.  It starts out blue, you put it into a tester, get the car warmed up first, and hold it at about 2,000 rpm.  Then put the tester with some blue liquid in it over the neck of the radiator and squeeze the bulb on the top.  What we don’t want to see is that blue liquid to turn to yellow liquid: if it does it means there’s exhaust getting into the cooling system and we have just proven that, and that means you have a major problem to deal with.


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