Cherokee Heater Valve

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.

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.

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

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.

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.

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.

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.

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

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.