Coolant pressure test - bleeds and holds at 15psi
 

Hey team thirdgen

ironing out some I hope near final kinks to get my 91 TA confidently back on the road. Recap its a crate L31 that has barely break in mileage. Have been observing coolant disappearing from the overflow. Most recently put a pressure tester on it (highly recommend) and noted it bleeds from 16psi to 15 over 5 mins or so and then stays at 15 (for the duration of the test which I've had one for about 30 mins). Hoses and clamps checked and tight and split free to my knowledge. I also replaced the heater core on observing a slight leak which seems to now be fixed.

The test kit goes in placed of the radiator cap so not a case of the cap just bleeding down at its release pressure. It could be the pressure tester itself which wasn't a particularly high end unit; just the usual Amazon special.

With that, welcome thoughts. I'm thinking to put some dye in the coolant and see for subtle slight weeps I may have missed. One dreaded thought is could it be an intake gasket? Might only a slight leak mean it holds fine at 15psi, but anything more is leak-town? Its too slight I think to show as white smoke from the exhaust or a burning coolant smell

Am looking to take it for a much needed drive this weekend and observe

Re: Coolant pressure test - bleeds and holds at 15psi
 

Does the tester respond the same way on other vehicles?