All_Terrain_RX7

I did a search and did not find much specific information. I have an '85 GSL, manual transmission. The heater control valve is leaking around the stem on top of the valve. I've been putting up with it for a couple of years, but its starting to get worse. It looks like it will be possible to remove it from the drivers side. Here is my plan:
A. Remove plastic cover over control valve on driver's side. Single Phillips screw holds it.
B. Loosen hose clamp on bottom of heater control valve. I have already put a wrench on that.
C. There is a Phillips screw holding a pipe clamp on the back of the heater core box. The screw is facing the firewall. A right angle Phillips should get it with much difficulty. This clamp will need to be loosened to remove the heater control valve. I'm thinking do not completely remove the clamp. I might not be able to put it back.
D. Loosen hose clamp behind the heater core box. The nut on mine is facing the firewall. Should be able to get a wrench on it, again with much difficulty.
E. Once all of that is done, slide it out towards the steering column. Once the pipe is clear of the clamp on the back then I can probably pivot and come on out.
F. I would like to replace the short hoses while I'm at it. They are only 30 years old. Anybody know what the ID of the hoses are?
G. Install the new valve in mostly the reverse order. Turn the hose clamps to a position that will let me put my ratcheting box end wrench on it.

It looks like an all morning job that will actually take all day, lying under the dash in contorted positions, using a flashlight and mirror trying to find what is still holding the valve. Just what an old fart needs to be doing.

I welcome input from anybody who has done this before. Have I missed something? Well, I forgot to list draining the coolant, disconnect the battery, notify next of kin...

Thanks, Eric

j_tso

iTrader: (2)

Pretty straightfoward as you've described, just a pain in the back. I took the seat out and had my face against the pedals with only my left hand able to do the unfixing.

I thought mine was leaking too a few years ago, turns out it was just the hose connections to the valve. Mazda decided only to use 1 clamp for each hose instead of 2. It's not elegant, but I used the hose clamps with the plastic butterflies so I could screw it tightly without trying to fit a ratchet in the limited space.

I don't remember the hose sizes, just that they were metric and between whatever sizes I could find at the local shop.

All_Terrain_RX7

I pinned my ears back and replaced the heater valve today. Here are some steps that might guide others:
A. While draining the coolant, disconnect the driver's side heater hose from the heater pipe. Connect a 5/8" heater hose to it and blow through it. This will push all of the coolant out of the heater core and down to the bottom of the radiator. Do this until you get the water out. Then put the hose back on.
B. Remove plastic cover over control valve on driver's side. Single Phillips screw holds it. Test fit the Phillips screw in the new heater valve. Drill out the hole larger if needed. I did not realize that my hole was too small until the install was complete. Anyone that thinks I pulled it all back out to drill out the hole does not need to read any further.
C. This step is for us old farts: Take the driver's seat out. This gives lots of space. Lay your tools on the garage floor (or ground) next to the car where you can reach down and get them. Get a small pillow for your head too. You younger guys are laughing, I can hear you.
D. Loosen the hose clamps for the heater valve. A 10MM wrench fit the OEM clamps. The one behind the heater core requires patience. That's when it's nice to have the pillow.
E. There is a Phillips screw holding a pipe clamp on the back of the heater core box. The screw is facing the firewall. I bought a Kobalt Ratcheting Offset Screwdriver Set: Item #: 239459 | Model #: 60359 from Lowes for less than $10. Money well spent. This clamp will need to be loosened to remove the heater control valve. I loosened it a lot, but did not completely remove it. You might not be able to put it back.
F. There is a Phillips screw that holds the heater valve bracket to the heater core box. Set the temperature control to cold to expose it. Remove the screw.
G. Disconnect the temperature control linkage from the valve. I think I put it in the fully hot position to get it loose.
H. Here is where it gets fun. My pliers have jaws that can hold a hose. I started gently working the hoses back and forth until they finally broke free. The valve came out of the lower hose pretty easily. To get it out of the hose behind the heater core, I used a screwdriver to pry between the side of the heater core box and the heater valve pipe. It finally popped out of the hose.
I. There is a copper pipe blocking the space in front of the heater valve. You'll have to do a little twisting to get the valve out. It won't come straight out. I rotated the valve up to the 2 o'clock position, and rotated the bottom out. I had to really loosen the bracket on the back, and then used a screwdriver to pry a little on the bracket. The valve finally came out from behind the heater core box.
J. Getting the valve from behind the other pipe requires rotating it around to find the path that works. I'm not going to try and describe all the turns I made to get it out. Just be patient and creative. Again, the pillow was a good idea.
K. Put some antifreeze on your finger and rub it around inside the hose behind the heater core. I did not do this at first, and could not get the new valve to go in the hose. Also put some on the heater valve pipe. Pushed the valve pipe into the hose and made sure the valve bracket fit properly against the heater core box.
L. From there its pretty much do everything you just did in reverse. I would leave the plastic cover off of the heater valve until you know you don't have any leaks.
M. Put the seat back in. Fill with anti-freeze (50/50 mix) and check for leaks.

The whole thing took about 3 hours, including taking the seat out. Its not as hard as I thought it would be. Just be sure to give yourself plenty of time. There are many steps that require patience and may not move very fast.

I had some 5/8" heater hose and hose clamps on hand in case I decided to replace the OEM hoses. 5/8" is a little snug. The OEMs were in very good shape, and replacing them looked like it would be a real bear. So I left them in. We'll see if that was a mistake.

Thanks, Eric

LongDuck

Nice writeup, thanks for posting it!