Do you think the heater core is failing in my 77 New Yorker?

[WissaMan]

I was troubleshooting the ATCII the other day, idling the car, putting the system through it's paces with a tester box, etc. I won't go into the details of that here (it's a basket case) but after I moved the car I noticed a puddle of antifreeze on the garage floor. Unfortunately I didn't see where it came and since the car was moved I couldn't eye up where it dropped from. I suspect the heater core but I couldn't find any evidence of leaking inside the car and the little rubber drain in the engine bay felt dry on the inside when I stuck my finger in it. I also couldn't see any wetness on any part of the car.

Tonight I started the car, drove it a couple miles, parked it, idled it, pulled the vac hose from the valve to be sure the coolant was flowing into the core. Revved it, let it idle, etc. basically everything I did the other day, and no leaking that I could see.

I read another thread here that talked about doing a vacuum test. I have a vacuum pump so could do it, but even if it tests good I'm going to be nervous about it. I'm already 1/2 way into this and wondering if I should just replace it to be safe.

 

[413]

2 things happen when the heater core leaks, coolant on the floor. Then when it's hot you have steam from antfreeze to breathe and the windows fog up from it. Not a good smell.

 

[WissaMan]

Hmmm...I wonder what it could've been then. I didn't smell any antifreeze in the car but I'll check around the floor again. But if not the heater core, then I wonder what it could've been? Maybe I should put some dye in it, drive it around and look for leaks.

 

[413]

So you got coolant on the floor once and now the heater core is the culprit?? Was the engine hot and it came out the coolant overflow?

Many many places where it could have come from besides the heater core.

 

[WissaMan]

I thought about the overflow, but the bottle is only about 1/3 full. The reason I suspected the core is because I've been driving this car for weeks with no sign of an antifreeze leak. But the day I'm working on the AirTemp, which opened the water valve to the core, I notice the puddle. But I hope you're right. I'll be buying some dye...

 

[Robert Saigh]

Mine was partially blocked with a little dirt that didn't get cleaned/flushed out!

 

[MONC440]

I wouldn't vacuum test it I would pressure test the entire system. Normal systems run 12 to 16 PSI depending on your cap. Check what cap you have. I would fill the system, pump it up to 2 PSI over what your cap is (18 psi MAX) and watch the gauge. If it drops over an hour or so start looking for your leak. Should be easy to find with the car sitting still.

 

[WissaMan]

I put the UV dye in it and drove it home. After dark I checked it with the UV light and the only evidence of a leak I saw anywhere was a small weeping leak around the heater hose where it connects to the water pump. Nothing under the car and nothing inside. I've seen where a bad coolant hose can leak sometimes more than other times, so hopefully that's all it was!