so ive been trying to get my heater to run hot and at best it runs luke warm.. im gussing somewhere in the 70 deg range not nearly enough to warm me up on a cold day, here is what i have tried so far

checked that the motor that moves the door from the a/c to heater is operating properly and it is, the arm moves and i can hear the door moving inside the box under the dash.

used a hose to reverse flush the heater core (there was flow but not really as much as i would have liked)

complete system flush with the leave in cleaner (absolutly no change in temp after a 6 hour drive)

the engine does not over heat which leads me to believe the thermostat is operating fine.

one thing i noticed was that while under the dash if i felt the heater core in and outlet sides the inlet was hot and the outlet was cold. this lead me to believe that the core was pluged but after the reverse flush and the cleaner i should have noticed SOME improvment..

in another thread someone meantioned a water control vavle... what is that? where is it? what does it do?

thanks guys!

 

I have ran into the thermostat sticking open causing it to take a long time before getting warm.

 

How did you do this?

 

crawl under the passanger side of the dash and undo the screws to the little acess pannel where the motor is, then disconnect the motor and move the armature by hand hearing the door shut and open. then re connect the arm and use the motor to do it. both worked fine.

 

Thank you for the explanation.

 

stupid question,

Is the system full of coolant? since the rad is so low on the fd it will suffer if its missing a decent amount.

 

im having the same issue with mine. i'll let you know if i figure anything out before you. it sucks going to work frozen!

 

I had a plugged core that took multiple flushings to get it fixed (search around, there is a whole thread on it....OLD though).
What you describe sounds exactly like what I had. Inlet being hot, outlet being cold meaning no flow thru the core.
I went from no heat to nuclear heat...so it CAN be done.

Good luck.

 

thanks, i tried flushing with CLR (just the core not the block) and it helped some. i got about another 10deg out of it.
ill keep working at it *sigh*

 

What I did was to get a small pump like a Little Giant submersible, and put it into a 5 gallon bucket of hot (130 degree) water that had a strong mixture of Castrol SuperClean in it, and I hooked one end of the pump up to the inlet of the heater core and the exit out of the core into the bucket via some rubber hoses.
Circulated this for a while, got a bit of stuff out but not much...had a trickle coming from the discharge side. All sorts of crap had flushed out (I should mention my core was plugged due to using block seal to fix an 'O'ring leak prior to rebuilding my engine). Then I did the same thing with PRESTONE radiator flush, I think I put 3 or 4 bottles into the bucket that held three gallons or so of water. Ran this for about 24 hours, came out and found I had a NICE return flow into the bucket. Basically I repeated this process until I had nearly no backpressure on the inlet hose and nearly full power return stream. Took several days of funking with it but the results were phenomenal.

Good luck!

 

I need to do this too, any pics of how you hooked up the inlet and outlet? I dont want to flush the radiator or anything like that, just clean out the heater core... is that what u guys did?

 

What is the material that is usually built up inside the heater core?
Is it just calcium from improper coolant mixture ratio?
Maybe causing the material to insulate the core from taking heat from the coolant?

Is there any acidic materials or materials that dissolve whatever is in the core into solution, but leave the base metal of the core unharmed?

I have flushed my core for a long period of time both directions, (thing has great flow, and little restriction) but still get less than luke warm air out of the heater also.

is CLR a OK material to be flushing a core with?

 

I think I'd be careful with CLR...doesn't it say on the bottle that it etches aluminum? I had good luck with PRESTONE Radiator Flush.

 

I'm having a similar issue but i definitely have a thermostat problem.
I plan to address it over the next few weeks.

Car won't stay warm/would take a while to warm up. Any highway driving and the temp gauge would literally drop along with the PFC readings.

Maybe my Fluidyne radiator is that good....

I plan to do the Heater Core process also while i'm at it. for process Bajaman.

 

Wow I've just always thought the heater sucked in RX-7's. I'll def try what Bajaman described!

 

I think I just figured out how I killed my heater.... I will try your fix, I don't think that I could make it worse..