well for piece of mind, buy a new oem thermostat while your at it, no sense in draining the coolant twice, a stuck open thermostat can also keep your car from blowing heat. I would replace that too, before topping off your coolant system, not many other issues can cause lack of heat other then steps you've taken, or the heater core is taking a dump.

 

But wouldn't a stuck open thermostat not allow the car to reach operating temperature? Because my car does reach normal temp and stays there consistently. Even in the freezing cold.

 

well here's the thing when it comes to operating temp, the gauge might not be right on, or it might partially be open, not at full operating opening temp but close. So the gauge might be showing full warm operating temp, but you could possible be 10-15 * f colder then what the thermostat should fully open at. That's all i'm saying, and no a stuck open thermostat, would take longer to get to operating temp but it might not fully open, a stuck closed thermostat would cause it to get there and then possibly cause it to overheat. Either way to test thermostat, you have to remove it follow the manual and stick it in warm water. Or you can go cheap way by one of those temp laser guns, point it at each hose and point it at your radiator, and see roughly what temp the coolants getting to at operating temp.

 

You've been under the dash, changed the radiator and antifreeze, flushed the heater core but never touched the thermostat. Try a new OEM thermostat.

 

^^ this guy, yup I tried telling him, and if hes not doing the work till tomorrow or something, might as well change it with coolant drained, its 3 bolts and take the thermostat housing cover off, new gasket and new thermostat, bam 15 mins of work if that.

 

Okay okay, you've beaten me into submission. I'm going right now to a local Mitsu dealer to pick up an OEM thermostat.

I'm still not clear as to why a thermostat would be causing this problem in my case. I say that only because the car heats up to the regular operating temperature, per the OEM gauge, and stays there. If it were truly the thermostat being bad it would cause one of two symptoms: First, it's stuck closed and the engine over heats or second, it's stuck open and the car takes forever to heat up and/or never reaches full operating temperature. I'm definitely not over heating and unless the OEM gauge is WAY off, I'm either reaching normal operating temperature or very close to it. If I'm missing something, please tell me.

 

One thing that I have done to mine as a temp fix for heat is manually move the lever on the side of the blend box by hand. My temp knob is unhooked because its broken so there is nothing connected to the lever that changes it from hot to cold. Mine got to where it would only blow warm air, then I got under the dash and realized that the lever was stuck half way. Move it to one side or the other, depending on wether it gets really hot or cold when you do this would help determine if its a gear problem, or one of the others listed above.

 

WS111,

Thanks for the input! I actually did this last night, I removed both gears for the blend box door and moved the door by hand. It moved easily with no obstruction and slightly changed the temperature of the air from the vents. So, I know it's working and it didn't fix my lack of heat problem. But again, thanks for the idea.

 

UPDATE:

After flushing the heater core and replacing the thermostat, I have some heat! It's not where it should be and it's still pretty luke-warm at idle. BUT, it gets pretty hot once the car gets moving. I'm almost positive the heater core is still slightly blocked/gunked up. It will probably need to be replaced. But I do have some heat and once I test it in some decently cold weather, I'll make the decision on whether I want to pull the dash and replace it or just live with only ehhhh heat.

On the A/C side, I don't have any refrigerant in the system. So, I'm going to have my buddy fill it with nitrogen and look for leaks. If no leaks he'll fill it up and hopefully I'll be good to go.

 

its not the heater core, a flush would help my guess ur gears arent lined up so when you have the knob set to hot, its not fully blowing hot....i had a similar issue with mine, havent replaced gears yet and heat/cold knob is hard to turn, turned it all the way to hot. Blows hot. Glad to hear the thermostat helped, there really isnt much else in the heating system short of a new hvac unit that can keep that from happening. Dont worry about the a/c side, just dont turn the air to cold side, or press the a/c button youll be fine until you get it fixed.
good luck

 

I'm pretty sure it's the heater core. I have already replaced the original gears on the HVAC unit with the new revised ones. Also, I removed them and manually turned the door to full hot and it didn't make the air any hotter. So, I've already determined it's not the blend door. It moves freely and changes the temperature of the air.

You don't understand the history of the car. This car was being turned into a "time attack" car at one point by the previous owner. Everything on the car was removed for a full respray and then sat for a very long time. When I flushed the heater core, I had chunks of debris come out (I'm thinking the heater core is clogged with a whole bunch of crap). I think the little I got out did help improve flow through the core but it didn't fix it completely. If you can tell me where I'm going wrong in that thought process, feel free to point it out.

 

Agreed.

Good Luck with the heater core!

 

Thanks! I'll again post some updates as I remove and replace the heater core. Not looking forward to it at all.

 

If you need any help let me know. You can PM me and call or text me as well if you need to.

Before you go completely crazy and pull the mix box and all the work associated with that (I've done it twice now) I would pull the main dash piece (giant black plastic piece) and then see if you can look down inside the white mix box from the top. You can accomplish this by flipping the gears near the top of the mix box so that the "door flaps" on the top open up. You can see down into the box and you should be able to see the blend door in there. Use the lower set of gears to move them and see what happens when you flip them around. See if that black blend door moves back and forth.

 

Ray, really appreciate the offer! I'll definitely shoot you a PM to get your number so I can contact you. Just out of curiosity, what does looking down and checking the blend door do for me in this case? Is that just to confirm the blend door is actually moving it's full range?

I'm still pretty convinced it's a blocked heater core. Now, here's a question for you. Is the heater core located in the blend box housing? Do I actually have to remove EVERYTHING per the HVAC-Mega Repair Guide to get to it? I've never worked on this system before so it's all new to me. Thanks!