Working on my engine temperature issue today and I rented a cooling system pressure tester. I first tried to test my new DMCMW radiator cap (Made in England, 15 PSI). I could not get any pressure at all to show on the gauge. Trying to decide if I should rent a different tester, or even buy one, but I won't bother if these testers don't work on the OEM cap. Note that the OEM cap does not have a rubber gasket on the big metal disc but an aftermarket 16 psi cap I have does (and does hold pressure on the gauge. Can anyone confirm that these caps can't be tested, or do I just have to find a different tester with a different adapter design?
By the way, I know the 15 psi cap certainly holds some pressure because I don't have coolant boiling out everywhere and after 90 minutes of the car being parked there was still pressure behind the cap when I removed it to check header bottle level. It's just not helping my diagnosis if I can't be sure the cap works on a tester.
This tester also shows I have 11 PSI in the system after 15 minutes (originally pumped to 15 PSI), but I think any loss is just around the pump because I can hear a tiny sizzle coming from around there and there are no visual leaks on the car. Perhaps a different tester would fit or hold better.
Original style cap - 15 PSI made in England
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Aftermarket 16 PSI cap
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