Coolant leak from under blower motor box?

[Jake And The Exploder]

1998 5.0 AWD: Any ideas where this might be coming from? I quite literally just did the heater core last week and it solved the leak for about a week and now it’s back…it’s coming from the bottom of the blower motor box on the engine bay side. It seems to only leak for about 10-20 mins after running, pretty small amount, the reservoir doesn’t seem to be going down too fast either. I’m just about to leave for a road trip and thought I’d throw the question out there, thanks!

 

[Turdle]

Your heater core has developed a leak, and needs to be replaced.That is the one and only source of coolant in the blower box.

Ac condensation will drip also. Possible it is mixing with residual coolant in the box?

Also check the heater bypass valve, it possible that it may be dripping down into the box?

 

[Jake And The Exploder]

Your heater core has developed a leak, and needs to be replaced.

Just replaced it last week

 

[Turdle]

Might ba a bad replacement part. Which brand did you use?

Not what you want to hear, I know. Good job on replacing it, it's not real fun. I guess now you get another

 

[Jake And The Exploder]

I suppose that could be the problem, it was a some “replacement” brand from CarParts.com

 

[Turdle]

Idea I had just now,

Before changing it, if you can, fashion some way to apply pressurized air to one side of heater core, while blocking the other, to see if coolant sprays out, or, if there is a leak you might hear it.

 

[Motorhogman]

Idea I had just now,

Before changing it, if you can, fashion some way to apply pressurized air to one side of heater core, while blocking the other, to see if coolant sprays out, or, if there is a leak you might hear it.

Testing a heater core before installation is industry practice in radiator shops. I've never in my life installed a heater core in anything without pressure testing it.

 

[Turdle]

Testing a heater core before installation is industry practice in radiator shops. I've never in my life installed a heater core in anything without pressure testing it.

That, and test the one suspected of leaking, just to verify it is. Quite a job

 

[EB4X]

Just replaced it last week

View attachment 444940

Good times......good times........

 

[Turdle]

Were you able to go on your trip?

 

[Jake And The Exploder]

Were you able to go on your trip?

Yup! Bout 800 miles round trip and she seemed to do great. Definitely leaked when the heat was on but I just didn’t use it a whole lot. I also kept a jug or two of coolant in the back. It didn’t end up being an issue for the trip.

Looks like I’ll be replacing again tho which is a bummer, ah well it wasn’t the worst thing I’ve ever done.

 

[Turdle]

Yup! Bout 800 miles round trip and she seemed to do great. Definitely leaked when the heat was on but I just didn’t use it a whole lot. I also kept a jug or two of coolant in the back. It didn’t end up being an issue for the trip.

Looks like I’ll be replacing again tho which is a bummer, ah well it wasn’t the worst thing I’ve ever done.

You can disconnect both hoses from the heater core and use a double barbed hose union to rejoin them for temporary use. It's perfectly safe, but might make you put off the inevitable until frost sets in.

 

[410Fortune]

Before dropping the dash again:
Make sure it’s not one of your hoses and fittings. I know it’s a long shot that the coolant could reach the inside, but it’s worth a check

Make sure it’s coolant and not a leaky windshield or door seal

Test the new core, you should not have to do this with a new part… but with the amount of labor needed to pull the dash it’s not a bad idea
The aluminum cores should last the life of the vehicle. Backflushing them every 100k miles is a great way to keep them like new