Hopefully this helps other HDJ81 owners (I have a 1991 HDJ81 with about 257,xxx kms) out in regards to the HDJ81 Heater Control Valve replacement. Since the OEM Denso version is discontinued and no longer available I wasn't sure what to do. However...@SteveJackson helped out big time! And
@SteveJackson deserves the credit for this find...in his Post #27 earlier in this thread he mentions that you can use a Murray Part #74642 Heater Valve as a replacement for the RHD HDJ81 heater valve (see
HDJ81 Heater Control Valve - https://forum.ih8mud.com/threads/hdj81-heater-control-valve.827718/post-11932985). I am HAPPY to report that this heater valve does in fact work, but it involves some minor modification of the white plastic keyhole where the metal armature connects to the heater valve body itself. The Murray heater valve was about $22 at O'Reilly's, but I had to have it shipped to the store, as they did not have it in stock in the store, FYI. I also needed to get some 5/8 in Gates Heater Hose to replace a tiny section of the original heater hose.
To do this heater valve replacement was not that difficult and I did not lose more than a quarter cup of coolant once I opened up the system. Since the heater valve is near the top of the vehicle's coolant system there is not much to push out of the system
The hardest part I encountered was the removal of the existing short section of heater hose to the left of the heater valve when viewing the heater valve from the front of the engine. Since I have a 1991 HDJ81 the original heater hose was pretty stuck. I also learned about a different style of Toyota clamp that uses a "pin" to unravel/reel up a small metal band.
You can view the photos below to see what i did.
Below is what my old heater valve looks like in my 1991 HDJ81. You can see some pink crust around the plastic valve, somewhat where the lefthand heater hose meets the plastic valve body. I never did find a crack or source of the coolant leak, but it must have been tiny and only apparent when the system heated up. As you are probably well aware, if this heater valve fails (i.e. the plastic connectors disintegrate or crack) you can lose a lot of coolant in very little time. Replacing this heater valve is great preventative maintenance!
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Next I disconnected the end of the cable (i.e. the cable that links the inside climate control slider with the heater valve) from the armature on the existing heater valve in the engine bay. I had the inside climate control slider set to "cold" so that the cable was fully retracted. This was pretty straight forward as there is only a metal clip that you need unclip to in order free the cable from the heater valve armature (the metal arm). You can see in the photo below the metal clip and cable end that I'm talking about.
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I then removed the heater hose on the right side of the heater valve when facing the heater valve head on. It involves unscrewing a screw-tensioned clamp. I reused this heater hose and the screw-tensioned clamp as they are both in good condition (the right heater hose had been replaced a few years ago and is not the original one, fyi). Know that once you remove the heater hose from the the heater valve body you will lose a small bit of coolant. In total I lost maybe 1/4 of a cup of red coolant...not too bad. Below is a photo with the right side heater hose removed.
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Next I removed the old heater hose to the left of the heater valve. It took me awhile to figure out how the clamps functioned. To loosen them you simply turn the pin so that it loosens...you do NOT try and remove the pin by sliding it out like I thought...that was the a-ha moment for me
Below you can see I used a nail punch to "unscrew" or turn the pin so that it lets out the metal clamp tension. I did NOT reuse these clamps as I felt like they are somewhat of a one-time use clamp.
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The left heater hose was the most stubborn to remove and I had to eventually cut it off the metal heater pipe, taking care to not nick/scratch the underlying metal heater pipe. The left hand heater hose was definitely original and I did NOT reuse it. In its place I used Gates 5/8 Heater Hose.
I then loosened the entire heater valve from the engine bay by using a 10mm socket to unbolt it from the chassis. Now it was time to adapt the Murray Heater Valve to operate like the original Denso Heater Valve in terms of where the armature is when it is in the "open" (or heat) and "closed" (or cool) position. After looking at the new Murray heater valve I realized that I need to trim the plastic keyhole that orients the metal armature on the valve itself. I used a small hacksaw and very gingerly sawed off a small bit of plastic to make the keyhole fit.
Below is a comparison shot of what the Murray part looks like relative to the OEM Denso heater valve on the bracket. You'll notice the metal armature is 180 deg. opposite of what the OEM heater valve is. You'll have to "reclock" the armature to match the OEM heater valve, so to speak.
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To "reclock" the metal armature on the new Murray heater valve you simply undo the black screw and remove the metal armature. You'll notice there is a "house" shaped plastic keyhole in the white plastic below. Simply trim the white plastic looking "roof" portion of the "house" so that the metal armature will sit in the same orientation as the OEM heater valve arm when it is in the cold (or "shut") position. It doesn't require that much trimming...just a little bit. Now re-fit the metal armature so that it is oriented like the OEM was. Then put the screw back in. I then removed the old OEM heater valve from the existing mounting bracket and transferred the new Murray heater valve on to it. It was a perfect fit. The installation is in reverse, only I replaced the left-hand heater hose with some Gates 5/8 heater hose and used some stainless steel clamps to clamp it down.
I made sure all the connections were tight, but not too tight, and then started up the engine and drove around for awhile. Make sure the in-cab heater slider properly turns the valve so that hot is hot and cold is cold
That's it. No need to "burp" the coolant system or anything. Any of that air will eventually make its way to the overflow bottle and come out of the system...just make sure to have that heater on to encourage the coolant to flow through the system. Hope this helps other folks!
