I've been looking through all the old threads and I have some good info but still have some questions. I have an 83 and the motor is new. When I replaced the motor I changed all the hoses under the hood.

I have a problem with my windows fogging up, I know it is coolant because I can smell it and it leaves a residue on the windshield. I do not have any coolant on the floor so it must be a weep. I read that I should look at the heater control valve first. Also I read that there is small sections of hose the connect the control valve core.

To get to the control valve I pull the drivers side seat and it is behind the radio, is this right?

Is there a way to inspect the heater core without pulling the whole box?

I read that the valve can be changed out without removing the whole dash but can the little hoses be changed out as well?

Where can I get a new control valve?

 

I went through the parts catalog and found the parts number for the Heater Valve:

76-4090-8871

Mazdatrix sells it for $76.84 so it can be had.

I still need help with the other questions.

 

Never had this particular problem, but there's a gent doing a complete inside-the-dash restore in the non-technical section just now - - he might have pictures that will help you see where you're heading.

Mazdaverx713b's "L6 Project" thread:

https://www.rx7club.com/1st-gen-general-discussion-207/finally-got-my-l6-project-796342/

 

Thanks for the info. I've been following his build, nice car. I've also been following your build, I really like you car.

I looked though his thread and there isn't any real good pics of the heating setup.

Last night I looked under the dash to see if I could see the valve and I can. The valve is the problem for sure, there was coolant weeping from it. I'm not sure if the hoses are part of the problem though. I will be ordering the valve this week. Im still not sure if the core is also a problem.

 

Can anyone answer any of my questions?

 

Fix the valve first and see if it solves the problem. Then check/replace the heater hoses. If the windows continue to fog, the heater core has a leak.

 

Check to see if the heater hose pipes are bent / out of round where they meet the firewall. I have seen ones where someone grabbed the hose with pliers to remove it and bent the pipes in the process. How did they look when you replaced the engine?

 

Thanks for the help.

The heater hoses coming out of the firewall look good. The were round and didn't have any corrosion on them.


I will replace the valve and the hoses that are connected to the valve right no and see how it goes from there. The valve is ordered through Mazdatrix so it should be here before next weekend. While I have the valve out I will also be installing freeze plugs in the water passages into the intake and installing an FC water pump and housing. I also have a Taurus electric fan and a painless fan wiring setup. I figured since I needed to drain a little fluid I would get it all done at once.

 

it's probably the heater core.

you don't need to completely remove the dash to get the heater box out; just drop the steering column, remove the bolts both from under the dash on either side and also where it connects to the center console, then pry up the dash enough to get the box out.

its easier if you remove the seats too.

 

I will be starting to tear into this today so we will see if it is just the valve or the core also.

 

I replaced the valve and it seems to be working. Not a fun project, it took me half a day just to do the valve and the entire weekend for the whole project.

 

Yep, that's not a fun repair. Glad to hear you got it done.

 

I took a pic of where it is for anyone else that I will post tomorrow. The worst part was the hose on the back side of the box.