I have had my '98 Explorer Sport 4.0L V6 for more than 2 years now and have had to replace my heater control valve 3 times. For whatever reason, the valve seems to wear down and begin to leak coolant from the spring loaded arm at the top. In the past, I have discovered the problem without any harm done to my expy, and this time is no different. However, my sister's cat recently became ill which led to the discovery that this stupid problem was happening again. I feel terrible, but I had virtually no control over the situation. If anyone knows of, or has had this problem before please offer whatever advice you may have. Thanks.

BTW almost 50,000 miles since purchase and this has been the only maintenance required.

 

Having had the same problem and having installed a new faulty part once, the other thoughts given were vacuum leak or low vacuum pressure not allowing enough pressure to keep it sealed.

I"ve also been told you can just take it out and do away with it as its not that important.

Jeff

 

I had the same problem. Mysterious loss of coolant, finally noticed the leaking valve.

I just swapped out the valve last night. Replacements cost $18.00 at Autozone. It takes about 20 minutes to change it out. Only tool needed is a pair of pliers for the clamps.

If you fear your sister's cat was poisoned with ethylene glycol, the source may not have been your Explorer. Ethylene glycol is not as toxic as many people think. An animal has to ingest a fair amount of it to be poisoned. The leaking heater valve usually doesn't create all that big a puddle under the car (or even any puddle -- it usually hits the exhaust manifold and evaporates).

Many animals are poisoned with glycol, but the reason has to do with its sweet taste and not because it is instantly toxic in small doses. If substantial amount is present, the animal can and will ingest enough to die from renal shutdown. But a few licks at a damp spot on the ground is not enough to poison a cat or dog -- it's just not that toxic.

In case you are curious, the medical therapy for people suffering from glycol poisoning is intravenous ethanol. That's right, they hook you up to an IV bag filled with good old fashioned booze. I am not kidding -- look it up.

 

Replaced mine on a 97 and must have gotten a good one, not leaking (yet?) I agree that you can remove it for all heat all the time. Okay in the winter but in summer I'd want it fixed.

 

I'm no mechanic. But in years past there was no heater valve in the hoses. IIRC the advice about mine said it might keep the interior a bit warmer in summer but would not blow hot heated air etc..... IE not like a heater.

Am I wrong?

 

well, I really like the fact that I have mine in working order. Since the blend door is busted beyond simple repair I fixed the door in a mid point location. A/C max = cool air, no A/C = warm air. Simple enough for now. One day I'll tear the dash out and replace the parts myself... in the mean time that valve is doing good work for me

 

The labor, or the money for the part are not problems. I am worried about the consistency that this problem seems to be happening. I don't think i should have to replace this part before winter every year. Aside from that, I am slightly concerned that I caused the cat to be poisoned. However, there is no sure way to tell. Well, any other suggestions are certainly welcome. Maybe i have just received 2 bad parts from napa. Thanks.

 

my bad part was also from NAPA, BUT it leaked right away. IF that helps. I was told that there may not be enough vacuum pressure to keep tension on the shaft and therefore it leaked(napas thoughts) except that when I replaced it the second time it was fine.

 

hmmm... thanks rost. that kind of stuff is way out of my league though. i don't always trust the info given to me at the napa counter though. anybody else have an opinion on the vacuum pressure issue?

 

There's no vaccuum applied to the heater control valve (fail-safe) unless the HVAC control is set to MAX A/C.

Steve

 

For some reason, perhaps to deal with leaking heater cores, the valve has vacuum applied when the heater control is in the "OFF" position, as well as when it is in "Max AC". The valve is held in position by a check valve; if vacuum was applied when you shut the car off, the valve is held in positiion until the next start.

If you are in the habit of using the setting of "OFF", along with various heat/defrost modes as required, the valve will cycle each time you go to OFF. This wears the stem packing around the actuating arm, causing the leak eventually. My OEM valve lasted 9 years, but then I usually don't use "OFF", and switch from MAX A/C to HEAT only a few times per season.

I think the NAPA explanation is an absolute crock. Amount of vacuum has nothing to do with the stem seal. Furthermore, an Explorer has no problem providing vaccuum to the control diaphragm. And then there is the check valve that holds the arm in position.

I can offer one other possibility. If the dash control is mostly in OFF, or MAX A/C, and there is a slight leak in the vacuum hose or diaphragm, then the valve will cycle once per startup. It will then bleed back down as the vehicle is parked, This will cause extra motions of the valve arm, and more rapid wear.

 

fefarms -

Yeah, I forgot about the OFF position causing the valve to close. There's a caution in my Owner's Guide about not using OFF while parked so condensation doesn't build up in the cabin, so hopefully no one does that.

I agree about NAPA's "theory"; so ridiculous it's almost funny.

Steve

 

Thank you for the advice on the "OFF" position. That is certainly something i will have to keep in check. It seems kind of peculiar that there would even be an off position knowing that if used frequently, would cause problems. But i know that is something i do often.