Testing...heatercore?

Is there a way to test the heater core while on the vehical? I wana verify there are no leaks can i just flush it or do i need to go buy the plastic vacume controled valve (under hood) to even test it?


background: So i bought my sister a 93 xj 2wd 4dr. its pretty nice but needs some love before she gets it. The guy i bought it from broke the heater controle valve under the hood so the heater was bypassed under the hood. He said heater worked before.I have all the interior and carpet removed i am putting a new carpet in. The passangers side floor was all wet (been parked 4 2years) and mildued, was told it got wet from a door left open... belivable most the damage was back seat area and passangers floorboard.

We would test them air under water and look for bubbles. Obviously this is out of the vehicle. To test it in the vehicle, I would pull the hoses off the water pump and thermostat housing. Then blow out all of the liquid with a compressor. Plug one hose and put some kind of fitting in the other hose. Then you need to pressurize with a pump and gage and watch for the pressure to leak out. Another possibility is to use a vacuum pump and see if it holds vacuum. You don't even need that valve (ever) under the hood. It can be eliminated with no ill effects. The advantage to testing with pressure is that if you have a leak in the hoses or connections, you could find them with soapy water. Pressure should be no more than 20PSI.