Using a Pressure Tester to check for coolant leaks

[Early93Viper]

I am using a pressure tester to check and see if I have any coolant leaks. Per instructions from the manual I pumped the pressure tester up to 15 PSI and waited for two minutes. Again Per the 1995 manuals instructions if the PSI doesn't drop more than 2 PSI in 2 MIN than I don't have a leak. It dropped barely a millimeter (Maybe 1/4 PSI) in two minutes. And no visible leaks from any of the hoses. But I still thought that was weird it should be able to hold the pressure for 10 Minutes without dropping at all. So I pumped it up several times and timed the result every time I got the same figures. The pressure drops 1 3/4 PSI in 10 minutes. I got the same numbers when I pumped it up to 18 PSI, 17PSI and 16PSI.

First Question: Am I okay with a 1 3/4 PSI pressure drop every 10 Minutes?

I then started the car wet to operating temp (190-200) with the pressure tester attached. Pumped it up to 15 PSI. And the pressure tester was gaining pressure so I turned of the car.

Second Question: Did I perform this test right?

Thanks in advaced for the help.

-Dan

 

[dave6666]

I am kind of curious why the manual states it is OK to lose pressure during the test. A sealed system has no leaks...

When you started the car with the system pumped up you were doing pressure squared. The engine heating raises the pressure plus you pumped it up too, so that result you got would be expected.

To answer your question, it sounds like you did the test correctly.

 

[Early93Viper]

If this wasn't confusing enough after testing it this morning it's only losing 1 PSI over a 10 MIN period.

 

[Early93Viper]

Anyone else have any insight on the problem?

 

[SquadX]

I am with Dave, I would think a lose of zero would be correct but what do i know.

 

[jdeft1]

Perform the test cold. Pump up to 15 lbs, wait then look for leaks. If it loses pressure slowly as yours is (you probably have a leak at the fitting or through the pump valve), keep it pumped up for a half hour(+/-) then search for coolant leaks. None found?? good! Now, keep 15 lbs. on the gage and start the engine. Check the pressure gage. It should be steady. (jumping is bad and indicates a blown headgasket). If you want to, allow the engine to warm up but do not let it develope more than 15 lbs! The gage should be steady.

Lastly, let the car sit overnight then drain the oil. Catch the first quart or two in a glass (clear) container then set it aside for inspection. It should be a nice golden brown, showing no milkiness or seperation.... if it does, you need new headgaskets.....

If you're still not sure and it's a gen 1 with original headgaskets... Forget the whole thing and plan on replacing them.