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Cherokee Heater Valve

Sunday, October 26th, 2008

Yesterday I had a nice opportunity to do some work on my car so I used it to replace my rusted heater valve. This valve simply redirects coolant through the heater core when the heat is on warming the air getting blown into the car. The old valve was very rusty and seized up. When the climate controls are set to cool air, vacuum is applied to this valve to close the valve shutting off the flow of coolant to the heater core. When you change to heat, the vacuum is released and a spring opens the valve. The old valve was rusted enough so that the vacuum and spring weren't strong enough to move the valve, but up until last winter I could manually move it with a pair of pliers. Recently it had gotten so bad I couldn't fully open the valve even with the pliers, so I wasn't getting as much heat as I should since the valve was half open. All the hoses involved were also looking rather nasty and probably needed to be replaced anyway.

heater valve 1

Hot coolant flows from the manifold into the valve through the red hose. The vacuum motor (the dome looking thing) moves the valve so that it either flows directly out (the bottom black hose) to the water pump or through the firewall into the heater core and back out to the water pump.

This valve is pretty pricey new so I looked around and I was able to find a used one on ebay for a late 80's Wagoneer for $10. The new one is made of plastic, so it'll never have the rusting problem the original one did, and the ports are more conveniently located on the new one, so I can have shorter hoses at less awkward angles. The seller said even though it was used it didn't leak and worked perfectly; I was pleased to find out when it arrived that this was exactly the case.

This just shows you how the new valve works. There is a vacuum line attached to the top and when you slide the temperature control from hot to cold, it opens and closes the valve.

heater valve 2

This is a shot of the lines in and out of the heater core.

heater valve 3

This is probably the nastiest hose in the system. Notice all the green crap at the end? I guess it was leaking a little already.

heater valve 4

It was really hard getting those heater core hoses off. Once I got them off though, I noticed that they weren't the same size. The top one (output) is 3/4" and the bottom one is 5/8". The new valve however only had 5/8" connections on it. Then I took a closer look and realized that the water pump also had a 3/4" hose on it. I guess that was the difference between the older Cherokee valve and the newer Wagoneer valve.

heater valve 5

Luckily I was able to find a couple of these adapters that went from the bigger to the smaller size hose. I would've been up in serious trouble if I couldn't lay hand on these things. I needed 2 of them (from water pump to valve and valve to heater core) and of the 3 local parts stores I called only one of them had these in stock and they only had 2.

heater valve 6

Having to use these toids put the new valve farther into the engine compartment, but I was able to position it so it wouldn't interfere with the distributor or the oil dipstick.

heater valve 7

It took quite a lot of hose pieces and clamps, but it they were all necessary.

heater valve 8

heater valve 9 heater valve 10

I didn't think to do some temperature tests before changing the valve, but now I get over 120° air, and I can actually adjust the temperature with the intended controls from within the car. When I went for a drive after getting this all together to test it, I started getting heat after just a couple minutes of driving when it used to take around 20 minutes to get any noticeable heat.

This job took a lot longer than it really should have, but at least there weren't any show-stopping problems. It took forever to get some of the hoses off because they and the clamps were probably 22 years old and I was trying to not damage things like the heater core connections. Then there was the whole hose size difference with an extra trip to the store.


Comments (4) Subscribe

#1 - Oct 26, 2008 at 5:48 PM
You kinda need heat living up where you are. Mine is going to the dealer in the morning for a problem. It hasn't been acting right for the past month, but I couldn't put my finger on it until the idiot light on the dashboard that says "service engine soon" came on friday night. Robert put his code reader on it the next morning and we got 3 codes, P2196, P0132 and P0053, all circled around the o2 sensor. So now we have an idea of what has been going on the past month. I called the dealer on saturday and scheduled it to be dropped off on monday morning. I'm hoping it is covered under the ESP warranty, but knowing Ford, it probably won't be. And my truck has 3 of those sensors, with 2 banks. It is indicating bank 1, sensor 1 with the codes. Computers!
Big Brother
#2 - Oct 27, 2008 at 10:41 AM
I would just make Rachelle buy me a new car. She's a big rich teacher and stuff...
#3 - Oct 27, 2008 at 10:48 AM
Funny! Although I heard through the grapevine that your father wants to buy you one of those boxy things....I think it was the Scion or something? I can think of something better than a box on wheels, which doesn't seem like you.
#4 - Oct 28, 2008 at 1:43 PM
Great description of function, outstanding pictures, the completed job looks more professional than the original Jeep engineering. As the sign on my toolbox (when I was in college)said, "Joe Reid can fix it".

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