Cooling System pressure test
- Thread starter Donald
- Start date
If your losing coolant try this with engine hot. You may need to loosen the spark plugs first (cold engine) so they can be removed for the test without harming the threads/head. With the cooling system hot and pressurized with radiator cap on, spark plugs out, have someone spin the engine over while you watch for mist and/or steam being blown out of the spark plug holes. If none you’re ok. If you see some mist and/or steam you probably have a cracked head or bad head gasket. Is your front windshield fogging? If so could be heater core…
Edit: sorry. It’s a boat engine. I personally think what you’ve described is ok. That much lose could be your pressure tester. Either way, good to go.
Edit: sorry. It’s a boat engine. I personally think what you’ve described is ok. That much lose could be your pressure tester. Either way, good to go.
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On a cold engine it should hold pressure but there are a few variables, the sealing of the cap adapter, the hose and pump. You will never get an accurate reading with air in the system, air compresses.
Well the adapter cap had a gasket to seal against the top of the expansion tank. The pump and hose are new. I would not think they would leak but who knows.
I will test my pickup and see if that holds pressure as a test of the pump and hose.
Wouldn't air trapped in the cooling system compress the same as the air above the overflow tank. Once compressed it would not cause the pressure to drop by 2 lbs in 30 min?
Would it?
The OP applied 15 PSI. The radiator cap itself is around 15 PSI in most cars, so the cooling system sees 15 PSI every time the car is driven.
Good point. I'll test my wife's Subaru. It's under warranty.
Unless he is double dog sure the gauge is correct on the tester…
I can go to 12 lbs? Not 15 lbs.
I pumped up the main cooling system in my pickup to 10 lbs and awhile latter it was down roughly 2 lbs.
Doubt my cooling system on my pickup has a leak.
So adapter cap not sealing? Pump or hose has a minor leak?
Doubt my cooling system on my pickup has a leak.
So adapter cap not sealing? Pump or hose has a minor leak?
Test the pump body, fittings, adapter cap, etc. with some soapy water while you have the system pumped up.
+1 If it cant hold normal operating pressure there is something wrong. Many caps are even higher 17-23lb. The only time I get concerned is with old vehicles that someone put an aftermarket 7lb cap on for some reason, red flag.
So got back to my boat after the rain and this time used the new air powered setup to do a cooling system pressure test. Used some water & Dawn on adapter cap gasket to lubricate it and the adapter cap key to tighten the adapter cap.
This time the cooling system held 15 psi for 20 min with zero drop in PSI.
So I guess I will be keeping the cooling pressure test kit I got on Amazon as it's got a bunch of adapters but use the air powered setup as I like the valve that isolates the hose, cap and gauge from the air supply.
I am up in the air about the manual pump included in the cooling system pressure test kit.
This time the cooling system held 15 psi for 20 min with zero drop in PSI.
So I guess I will be keeping the cooling pressure test kit I got on Amazon as it's got a bunch of adapters but use the air powered setup as I like the valve that isolates the hose, cap and gauge from the air supply.
I am up in the air about the manual pump included in the cooling system pressure test kit.
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