Persistent coolant drip

[Ajax MD]

I've snugged up all sorts of Class 1 and 2 drips on this HMMWV since I bought it but I've got one last drip that I can't seem to stop.

There is a drip behind the passenger wheel, inboard of the frame rail. (at least, that's where the coolant drips off and hits the ground) The weirdest thing is, the drip stops when the weather warms up! This indicates that something is swelling or expanding just enough to stop the drip. I lose about 2 quarts per month at the current drip rate.

I've checked the water pump and it's bone dry all around it, so that's not it. I've snugged up the hoses on the metal radiator piping and it now appears dry. I know the transmission and transfer case have a cooling circuit but I don't quite know where the connections are.

What is on the passenger side, near the rear of the engine that could be leaking?

 

[Bulldogger]

Heater core hoses? The core itself? Mine seeps, and I need to replace it. I just HATE replacing heater cores.
Other than the core, the other connections you can see to visually check (if I recall correctly).

Failing that, it could be degradation of one of the visually-OK hoses at the clamp point. Depending on what type of hose clamps are used, some models bite hard into the hose when over-tightened. In time that can degrade the hose just enough to leak or weep, and I've seen intermittent leaks like that.

If you haven't replaced all the hoses, this might be a good excuse. They're not terribly expensive, and peace of mind is always a good price. Would also obtain and install good quality clamps that don't chew the hose at the same time.

Bulldogger

 

[Ajax MD]

Hm, I hadn't considered the heater core itself. Thanks for the tips, I'll check that area out.

 

[papakb]

When I first got my truck I had a rust pinhole in the heater valve that would let out enough coolant that I could smell it but it wasn't dripping. It eventually blew out and was easy to find at that point.

 

[Ajax MD]

Ha, you guys are wise. I found the large hose on the bottom of the coolant expansion tank was loose. The hose was wet on the underside.

None of the hoses are dry or cracked but some seem kind of spongy so I'll look into replacing them.