Coolant pressure test
 

Getting frequent low coolant level light and borrowed a tester from Autozone. Injected 10 PSI and walked away for 5 mins and it was back to 5 psi after seeming to hold at 10 for 2 mins. Not hearing any air release or seeing any coolant escaping although I haven’t pulled anything off the get a better look.

Question: how much pressure gives a fair test? 10 psi enough?

3.0 inline 6, good places to suspect leaking?

The leak must be very small, maybe even a bad sensor as the level indicator is at the top when I pull the cap.


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I have a threaded adapter that converts the bleed screw thread (M10) to a standard air fitting (1/4 NPT) - male M10 to female 1/4 NPT .

I then put 17-19 psi (less than what the cap is rated for) into the cooling system and look for leaks. I would probably turn the key to run and turn heater up to 90F to open thermostat. Then look for leaks.

If I don't see it after this, I will add one half bottle of Coolant Ultra Violet dye and use UV sunglasses and a UV flashlight (all bought on Amazon for cheap) to find my leak...The last hard-to-find leak was coming from the Heater control valve...which I had previously rebuilt with new seals....Wooops!

Coolant pressure test
 

Good idea, thnx.

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Another sneaky place it can leak is at the temp sensor o ring on the side of the radiator. The leak is hidden by the sensor and it is very slow. It showed up with UV dye right away.

Check the small connection at the tank neck area. On mine, the inside lip holding the o ring broke off. The broken piece came out as a full ring! Years of vibration cracked it off.

Where the two heater hard pipes enter the block behind the oil filter housing.

Here you go!

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