Leak testing radiator at home?
 

Yesterday I bought a heater core from a used parts dealer but Im afraid its leaking. I run it with my submersive pump connected to the radiator and the other hose expelling the water out of the radiator in the bathroom sink. Fresh water comming to the pump from the sink. No water block was connected. After leaving the system for 10-15 minutes I realised a small wetness on the radiator surface, not really drops just a small glancing of wetness, but evident when you touch with a finger. Actually i could feel it on all radiator surface.
This is my first radiator (core) so i really dont know what to do. Before i return it to the dealer can I be sure its leaking or not?
Any suggestion highly appreciated.

Thanks in advance!

Was it cool water you ran through the rad???

Maybe it was condense... Sometimes when leaving the tap on for some time on cool water the whole tap will be filled with little waterdrops... Thats because the temperature of the water is lower than the air around it... Try it out wit warmer water...

An easy test(if you have a fairly strong pump) is to just block off the exit... and watch for drops and small sprays of water....:)

Yes it was cold water, will try with warmer.
Thanks

New heatercores are usually tested for leaks, at 25 psi.

You can fill it with water, block the outlet, and fashion a tire's valve to the inlet, then start pumping (to 10-15 psi). You must have an air gauge though, and it should be in-line, not the kind you use to measure a tire's pressure.

You can also color the water: it'll take away any doubt.

Seems the wetness was really a condensation and the rad is ok. Thanks to all for help.