Where did this water come from?

['74 Sport]

Something very odd here. I replaced the heater core with a new one in Aaron's factory A/C-heater unit in his Dart Sport. After we got the engine running for the first time last week, we ran it through its initial break-in paces. Later, when we were about to go home, I noticed a small puddle of water in the passenger floor. There was evidence it came from directly above the tranny hump and trickled down to the floor. My first suspicion was that the new heater core was faulty. We have been back to the shop running the engine several more times since then, and each time I look for more water, but there has not been any more since that first little puddle.

Is there any explanation for that?

Jerry

 

['74 Sport]

Guess I should also mention...
The A/C has been out of the car for two years. No condensation and no chance of residual moisture in the housing. Bodywork has been done for about six months, so no wet sanding.

Jerry

 

['74 Sport]

I already suspected the heater core, because there aren't any other logical reasons for water to get into the car. But, what had me baffled was that it only leaked the one time, just after the new engine's first start-up. Also, this was a new heater core. We have run the car many times since then, but no more leaks.

Well, we solved the mystery this weekend. We rigged up a tee fitting in one of the heater hoses and attached a pressure gauge. We pumped it up with air until the radiator cap released the pressure into the overflow reservoir (as it should). A quick peek inside revealed another leak from the heater housing. As much as we dreaded it, we pulled the A/C-heater unit out and replaced the "new" heater core with another. It turned out there was a small leak around one of the soldered joints. We're getting to be experts at this.

Here's a hint from someone who knows...
If you ever have to change your heater core, rig up a pressure gauge and check it for leaks under water, before you even think about installing it, new or not. Our replacement held about 20 lbs for several minutes, with no bubbles appearing, so I hope we are safe now. We would have been extremely upset to have it leak, after installing the new carpet.

Jerry