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Thread: My Home Made Cooling System Pressure Tester

  1. #1
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    My Home Made Cooling System Pressure Tester

    Here are some pics of my pressure tester.

    I started with an old radiator cap which I got from the wreckers for $2. It is off a commodore. They are the same as a D1.

    I then purchased a pressure gauge, (cost $20) one that does not go to high, found an old air fitting that screwed onto it. I then silver soldered it to a tubeless mag wheel valve.

    I then drilled a hole in the side of the stem and soldered a valve which I removed from an old tube.

    I then drilled a hole in the top of the cap and attached the tubeless bit to the cap.

    I then sealed off the caps pressure relief with silicone.

    I have a proper pressure tester but it only fits the older cars and I find this one to be more user friendly.

    Dave.








  2. #2
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    I've got an issue with my system - fix one area and something else splits, so I'm going to have a go at making one of these to check the pressure - it's a great idea.

    One question though, what kind of pressure reading is normal?

    Cheers.
    It's better to regret the things you've done than those you haven't!

  3. #3
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    Nice work. Well done.

  4. #4
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    I'd like to echo the question, what cooling system pressure is within normal limits? I too have some pressure related issues in my 300tdi D1.
    Just arrived: 2012 D4 3.0 HSE, the journey begins again ;-).
    Gone: 98 Disco 300tdi Auto, and some extras

  5. #5
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    I would presume you would test the pressure up to what the rad cap releif is set at - I am guessing at 15 -20lbs.
    Next time I am talking to my father I will ask him what pressure he use to test radaitors at when he ran his radiator repair business.

  6. #6
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    Well after some research the standard system has a relief setting in the expansion bottle cap of 15psi (103-104kPa), but it still doesn't let me know a normal pressure.

    I went to Bunnings and bought a pool filter pressure gauge for $20, which reads up to 250kPa.

    I was going to screw this directly into my old cap, but then I read that you can check for head gasket leaks by pressurising the system to around 14psi and check for a pressure drop. I was wondering why Mr Whippy had soldered on the tyre valve and now I know. I'm going to have to find a tyre valve to replicate his design - it's a shame that those available seem to be rubber.

    Will keep looking, but I might just try a rubber car valve in a piece of threaded pipe that my gauge can screw into one end of, whilst the other screws into the old expansion tank cap. Once I sort it I'll post pics.
    It's better to regret the things you've done than those you haven't!

  7. #7
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    Quote Originally Posted by Tyresqueal View Post
    Well after some research the standard system has a relief setting in the expansion bottle cap of 15psi (103-104kPa), but it still doesn't let me know a normal pressure.

    I went to Bunnings and bought a pool filter pressure gauge for $20, which reads up to 250kPa.

    I was going to screw this directly into my old cap, but then I read that you can check for head gasket leaks by pressurising the system to around 14psi and check for a pressure drop. I was wondering why Mr Whippy had soldered on the tyre valve and now I know. I'm going to have to find a tyre valve to replicate his design - it's a shame that those available seem to be rubber.

    Will keep looking, but I might just try a rubber car valve in a piece of threaded pipe that my gauge can screw into one end of, whilst the other screws into the old expansion tank cap. Once I sort it I'll post pics.
    15psi is the design pressure then. Most systems work up to the cap pressure. Header tanks are designed to expel excess pressure as air, that is why they should never be filled to the top.

    Tubeless car valves can either be fitted straight into a carefully drilled hole the same size as a rim hole, or you cut/scrape/sand the rubber off and expose the brass core, then solder or clamp on a piece of hose. Some tyre shops might sell solid brass tyre valves, they are installed from inside a rim and resist tearing out.

  8. #8
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    Most systems are designed to run at around a max of 16 psi. There would be a safety margin which I don't know what this is.

    What I do know is it is safe to go to 20 psi. You could have a very small leak which could be hard to find at 16 psi and by going to 20 psi could make it leak a bit faster therefore making it easier to find.

    As for the making of the tester, the bit coming out of the cap is a mag wheel valve. This is then soldered to a barbed fitting which I found that would screw to the gauge.

    The piece that is used to add pressure is an old rubber tubeless valve with the rubber removed. An easy way to do this is the wire wheel on a bench grinder if you have one.

    You also need to seal up the pressure relief in the cap. I did this with a bead of silicone around the inside of the cap under the rubber.

    Dave.

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