Quote:
Originally Posted by Bmwe5320023.0
2 questions.
1. Did you test cold or warm? If testing cold, I understand the thermostat will be closed, so only tests part of the system?
2. When you achieved the specified pressure, in your case 23 psi, how long did it hold this pressure?
How many minutes did you wait?
For example after 10 minutes, was it the same pressure, or did it drop and by how much?
This guide says it should not drop by more than 10% (2psi per minute). So does it mean 2 psi drop per minute is ok?
https://www.pelicanparts.com/techart..._Leak_Test.htm |
Done cold or warm. Definitely not hot (cooling system not self-pressurized due to temperature).
The thermostat is not a perfect seal (it will stop a significant amount of coolant flow, but it will not seal - most thermostats have a jiggle pin to purposely allow minimal coolant flow through the thermostat), so the pressure I apply with the pressure bleeder does pressurize the whole cooling system (except that I'm not completely sure how good the sealing might be in the HVAC system - set that on hot to be sure).
In my case there was no leak other than the forcing of a very small amount of coolant into cylinders #2 and #3 (if I remember right). That was the reason for the test.
The motive pressure bleeder is pretty solid, and does not leak. Going in through that bleed screw was done carefully, with no leak there. And the whole cooling system itself regularly gets under pressure, with no leak in my case. So there was virtually no loss in pressure. I think I kept it on there for a couple of hours at least, with no noticeable pressure drop, and then checked for coolant in the cylinders. Sadly I did find some, leading to the head gasket job about 6 years ago.
From experience with other cooling system pressure testers, borrowed from auto parts stores for other cars of mine, they are not so good, and the tester itself can leak, especially at the gauge. So for those, leaking down at a faster rate like you cite may be the case, making the test not so good.
So in your case, if you're pressurizing through the bleed screw, you should be able to put soapy water around that to confirm no leak at the interface. And if you use a good pressurizing system (whatever you may be using instead of the Motive Pressure Bleeder I used; and that may be the weak spot in the system here) that holds pressure, the only leak should be from your cooling system.