Cooling System Pressure Test

Reader Question

Austin, you replied to my email last week when I asked why my car was overheating and wanted your opinion. Thanks for the reply, but I am still not understanding your comment about getting a “cooling system pressure test”, what does that mean?



Hello Andrea,

I am soo sorry, I sometimes just ASSUME my readers can look inside my head and understand what I am trying to type.

A cooling system pressure test is what I recommend anyone do when they have an overheating problem or a coolant leak that they can not find.

Basically the test is just a small air pump that will attach to the radiator. The mechanic then pumps air inside the radiator (that is full of water) to help locate the leak.

This test will not only tell you if there is an external coolant leak like a radiator hose or water pump but it can also help determine if there is an internal coolant leak like from a leaking headgasket.

I would NOT skip this test unless you can obviously see the coolant leak with your eyes. This test will save you a lot of time and money guessing at the wrong part.

If your mechanic tells you the headgasket is leaking and he has NOT done a pressure test….run….run….he is just guessing and it is going to cost you a lot of money.

Prescription without diagnosis is malpractice :)

I found a really good video explanation of the pressure tester and how it works.


Austin Davis

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Posted in: Coolant Leak

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."
  • Austin Davis

    If your radiator is low on coolant a pressure test (not a COMPRESSION test) is the first thing I would do if you came to my shop.

  • Craig Mars

    I have heard about this cooling system preasure test but I didn´t got the idea what was it all about now I know better, I have a car that overheats but not always only when I use it many times a day.

  • Austin Davis

    Thank you so much Kev, glad to be of assistance. Let me know if you need any help from me.

  • Kev Black

    The test is very easy to do, when you watch the video you realize that it is not that difficult and you can save a lot of money by performing this test. I tried it on my car and when my neighbor saw what I was doing he asked me to teach him, I just pointed the way to your site, we love it, great posts!

  • Austin Davis

    Yes, getting the pressure test done is the first thing a mechanic should do to find a leak, unless it is obvious to the naked eye. If you skip this step, you will be wasting time and money guessing at things to replace.

  • Tommy

    Thanks for this information. We have been struggling with our older Ranger pickup overheating. This is helpful because now we know what to ask the mechanic and to make sure that they are being honest with us. There is no obvious leak with ours, so this will be our next check.

  • Austin Davis

    Hi Loyd, thanks for your comment. We typically leave the thermostat alone these days unless there is an overheating issue going on.

  • Loyd R McKinzy

    I own a 2003 Toyota Highlander with 88000 miles no heating problems but I curious about the thermostat. It has the original one in it. I remember when I was driving older cars in the 70’s 80’s it was a good idea to replace it every now and again.
    My question is in todays cars are thermostats better so its not necessary to change them so often?

    Thank you very much I enjoy your emails.