Heater Core Leak

[turbodaytona87]

I was pretty sure my new heater core was leaking. I could smell it, the window was getting greasy, steam out the vents, etc. I pulled the core again, and didn't see any noticable leaks, although I had coolant in the dash vent manifold, the floor vent ducting, and in the box itself. I filled up the sink with water, and pressurized the core with my air compressor (limited it to 16-18 psi) while it was under water. I didn't see any bubbling.

I had also tightened the clamps on the heater hoses before deciding to pull the core again.

Is there a better way to test the core before I put it or a new core back in?

[4 l-bodies]

I always check heater cores before installing new ones, too much work taking it back out if it is leaking. I pretty much use same approach, but use radiator pressure testing tool. Same end result. Coolant? Remmants from old leaky heater core? About the only other way it is getting in there would be leaking by the hose connections going through the firewall. Happened before you tightened hose clamps up?
Todd

[turbodaytona87]

I always check heater cores before installing new ones, too much work taking it back out if it is leaking. I pretty much use same approach, but use radiator pressure testing tool. Same end result. Coolant? Remmants from old leaky heater core? About the only other way it is getting in there would be leaking by the hose connections going through the firewall. Happened before you tightened hose clamps up?
Todd

I always noticed it more when in boost/at high RPMs. The entire assembly including ducting was washed/Clorox wiped before being put back together. There's no way this was residual. The foam around the heater hoses was soaked, but I didn't see the hoses actively leaking when I let the car idle. It was a lot of coolant though, even after tightening. I drove the car around 100 miles and it was still steaming.

[going4speed]

Take it to a radiator shop if you can find one close. The leak may not be apparent at room temperature with how you are testing. They have better equipment and expertise to test it.

[turbodaytona87]

Take it to a radiator shop if you can find one close. The leak may not be apparent at room temperature with how you are testing. They have better equipment and expertise to test it.

Good idea, I'll see if any local places will test it for me, depending on price

[looneytuner]

Put a dye in the coolant. You may have a head gasket going bad with what you described about leaking under boost.

[4 l-bodies]

I've also seen heater core hoses tightened to the point that they distort or crush the tube slightly causing leaking by the hose into the HVAC assembly. The under boost comment makes me wonder about HG issues too. Does coolant level change a bunch in recovery tank after running it hard?
Todd

[turbodaytona87]

Put a dye in the coolant. You may have a head gasket going bad with what you described about leaking under boost.

I had bypassed the heater core so I could drive the car, and no leaking. Head gasket is fairly new, but I know they can fail with boost/detonation. Coolant level didn't seem to change a whole lot.

[supercrackerbox]

FWIW, the heater core in the Charger seems to have a leak. Damn paper thin aftermarket aluminum cores.

[turbodaytona87]

No kidding, the heater core I pulled out was a copper one, and I'm guessing it's stock. It lasted 26 years, I doubt any replacement aluminum core will last anywhere near that long

Edit: It appears its a case of old stiff hoses. I also wonder if the nipples of the new heater core are slightly smaller than the old one. I hooked the heater core up in the engine bay so I could watch it, and coolant leaked out of both hose ends, even though they were clamped tightly. I went and bought some new hose and will start putting the car back together once the engine cools down and I can disconnect the heater core.

[supercrackerbox]

Bulk heater hose is cheap enough I never bother trying to reuse it. It's much easier to cut it off the pipes than to risk bending/breaking the heater core or radiator connections by fighting the old hose off.

[4 l-bodies]

...Edit: It appears its a case of old stiff hoses. I also wonder if the nipples of the new heater core are slightly smaller than the old one. I hooked the heater core up in the engine bay so I could watch it, and coolant leaked out of both hose ends, even though they were clamped tightly. I went and bought some new hose and will start putting the car back together once the engine cools down and I can disconnect the heater core.

With your heater core hooked up in the engine bay reminded me of the first time I ever heard of anyone intercooling a turbo car. It was like a million years ago, some guy decided to intercool his vehicle using a couple Harrison (GM) heater cores! I'm like huh? WTF? Probably pretty restrictive, but he claimed it worked!
Well, glad you figured out the problem. Might want to shop around next time for heater cores. The last one I bought was brass and it was at least twice as thick as the original. That car is long gone now, but the heater performance was way better than OEM.
Todd

[turbodaytona87]

With your heater core hooked up in the engine bay reminded me of the first time I ever heard of anyone intercooling a turbo car. It was like a million years ago, some guy decided to intercool his vehicle using a couple Harrison (GM) heater cores! I'm like huh? WTF? Probably pretty restrictive, but he claimed it worked!
Well, glad you figured out the problem. Might want to shop around next time for heater cores. The last one I bought was brass and it was at least twice as thick as the original. That car is long gone now, but the heater performance was way better than OEM.
Todd

Haha shop around I did, Amazon, all the parts stores, Google searches, ebay, all were aluminum unless I went with a Mopar part. That was over $200, mine was $170 cheaper. Honestly even after doing this job twice now (really not that bad now that I know what goes where), I wouldn't go back and spend the extra money for the Mopar core.