Dan12z

I noticed over the past couple of months that my anti-freeze is always low, about 3" under the minimum line but doesn't go any lower. I can always smell it outside of my car but i can't find a leak. I think it might be the heater core from want I've read but can't say for sure. Has any one experienced an issue like this or have any idea of what might be wrong? Also my windows where fogging up on the inside to the point where I'd have to wipe it off with a towel. I hasn't happened for a little while, not sure if that's a symptom of a bad heat core.

JimC

The most common source of coolant loss on the 4.0 is the plastic thermostat housing. It usually splits on the back side so the coolant sprays under the intake manifold, and is often misdiagnosed as a bad water pump.

Dan12z

I just came across that, there's a detailed video on how to replace it on YouTube. I'd welcome that over the heating core. Thanks for the info.

08'MustangDude

When it is the heater core, you would be able to smell coolant on the inside when you
have the heat on, blower on. This would be more of a sign that the core is leaking.

If you just smell it outside, then there is a leak in the engine bay. As stated, it's usually
the plastic thermostat housing. You can get metal ones on eBay... There are a few that
are listed for the ford 4.0, explorer, you need to get the one where the neck is facing the
same way as the Mustang's 4.0, and they're there, for under $50.00 if you look.

Dan12z

The housing does seem like it's the most likely problem. I was going to check today but it's -20c outside. I'll check on the next warm day and update my thread. Good to know about the heater core too.

Dan12z

Here is a pic of my thermostat housing. I couldn't really see coolant leaking but it seems like there's something going on around the glue seal.

Roger Baker

You should be able to rent a pressure tester at your local auto parts. Attach it to the tank and pump it up to 16lbs. If the gauge starts falling then you have a leak. Look around that plastic housing for sure. I looks like it has discoloration from leaking. If not you can pull the carpet back on the floor boards neer the firewall to make sure its not the heater core.

Dan12z

There's definitely neon green fluid dripping out, it seems to be a slow leak; I'll going to order a new housing. Thanks for all the help.