Pressure testing a radiator

(Thanks to Randall-in-Mpls for the information and pictures)

Here's a radiator test that I came up with when I needed to patch the Custom radiator I put on the Grub last year. I had it dismounted again this Spring to locate a slow leak, so I got some pics. (My patch held, by the way. The leak was near the thermostat.)

NOTE: I would be careful of the pressure setting on my compressor before charging the radiator with air. If the radiator cap was defective and didn't release at 13 lbs, you will be shopping for another radiator. I would suggest turning down the compressor to 15-20PSI max.

First, connect the inlet and outlet with a length of 7/8

...and submerge all but the base in a bucket of clear water.

Carefully pressurize the radiator through the drain hole. Any leaks will leave a stream of bubbles that you can trace to the fault.

If the pressure exceeds the 13 psi rating of the radiator cap, this happens. Wait a few minutes for the water to settle, and check again.

I hope this is helpful to someone. I've found it to work very well. R