Overheats and Heater Hose Confusion -'04 4.0

[MunkeyTX]

2004 Ford Explorer 4.0 EB 2wd, Aux Rear AC, Oil Cooler

I've had two random overheat situations over the past two weeks; the first was without any leaks or evidence of a leak, but the second had a tell-tale sign:

Ah-ha! Easy peasy, it's a simple split heater hose! A quick Google/Ford Parts search brought up part number "KH-72 Hose, Tee to Heater Control Valve". I thought I had this problem licked!

So I decide to remove the hose, to verify that it is split...and what do I find?:

Hmm...no splits, and hose looks to be in good condition, nice and supple...ok...so maybe the leak is at the heater control valve nipple that the hose connects to?

Nope, strikeout again. No signs of cracking. WTF??

Now here comes the kicker...that "KH-72 Hose, Tee to Heater Control Valve" is actually molded to the damn tee! I only realized this after I broke the hose away from the tee. Since I already poo'ed-the-bed and yanked one hose off the tee, I went ahead and broke away the other two hoses that were molded to the tee. Now take note: the tee was not leaking as seen by countless other members here...it was perfectly peachy.

At the very least, I'm going to need a new 3/4" tee regardless of what I do, and the dang "KH-72" hose...I'm gonna re-connect everything back up to the tee old-skool style via hose clamps and go from there.

So...can a hose look perfectly good, but still leak out? I truly do hope that my overheat issues were caused by this measly heater hose. The first had absolutely zero signs of leaking anywhere on the engine (including this hose/valve!) I fear that the only reason this hose was leaking is because the system was mighty hot, pressurized, and generally pissed off after the 2nd overheat, and this connection point just happened to be the weakest point in the system. As the pics show, everything looks dandy and nothing is overtly fubar'ed.

So what do y'all think?

 

[D Hook]

Weak hose clamp? Could replace with worm-gear style.

 

[MunkeyTX]

Update, just in case someone else runs into this issue...

I replaced the plastic tee with a unit from Autozone (3/4" all the way around), hooked up all the hoses to the tee and to the heater control valve, and also replaced all the spring-type hose clamps with worm-gear hose clamps.

Aaaaand, it's still leaking in the exact same spot. Cranked the hose clamp down more, and leaked MORE. No local dealerships had the hose in stock (part KH-72), however Amazon has the hose for $13'ish and it'll be here in two days. Before I hooked everything up, I eyeballed the hoses and closely inspected each one, especially the hose in question. They all looked just fine, very supple, no evidence of any cracks. Very interesting, indeed.

At least I know where all my coolant was going! The stream from the leak (more like a fast drip) would fall directly onto the ground, just barely skirting the oil filter housing in the process. It took approx. 1.5 weeks for it to leak out to the point of overheat, so the small amount leaked each day was not noticeable on my drive way...and even if I did see a small puddle or wet spot, I would have attributed it to A/C condensation, as it drains out on that same side, and almost in that exact same area. As noted in the pictures, the coolant was filled with rust, which is very concerning as I've only had to top off the coolant once since 2013'ish. I refilled the system with straight water on both overheat situations, so needless to say a flush and fill is in the works for this puppy!

If the new hose doesn't solve it, the next step is to replace the heater control valve.

 

[p71]

It's probably the heater control valve. The most common point for plastic fittings to leak is along the line where the mold formed the part. This happens a lot on the thermostat housing and the 4.6 intake manifold coolant passage.

 

[Bulletslinger]

Replace the heater control valve with a motorcraft from rock auto (or wherever you wanna get it, rock auto is a great price)

I bought a brand new HCV from O'Reilly's, don't even know the brand, but I don't care, it only lasted a few months before it started leaking again.

Motorcraft on, no leaks since.

 

[Bulletslinger]

You also might want to check for any signs of leaking around the thermostat housing/hoses

if you haven't already

 

[Joe in NY]

as an easy fix, you can just put in a straight male to male hose fitting. You don't *need* the heater valve. The only time it ever comes into play is when manual AC is set to MAX AC or when the digital AC is set to 60* on both sides. All other times it is open. Just be sure to plug the vacuum line.

 

[MunkeyTX]

You don't *need* the heater valve. The only time it ever comes into play is when manual AC is set to MAX AC or when the digital AC is set to 60* on both sides. All other times it is open. Just be sure to plug the vacuum line.

95*+ temps daily, with 75% humidity...you dang straight the A/C is at 60!

Anyways, I slapped the new hose on and she ceremoniously pissed a steady stream of water down onto the ground. Lovely. Time to buy a heater valve!