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Here’s my long, sad tale of misery ….hope someone has the answers: My 1992 626LX sedan is only blowing warm air ..and I’m getting worried now as the minus 30 stuff is well on its way!! (Western Canada)
This past weekend I drained the old coolant, took the old thermostat out, added a can of coolant system flush, re-filled the system with clean water, ran it for 20 minutes, drained out the water & flush stuff, and then also disconnected the heater core hose (top one), pinched the bottom hose closed and poured more coolant flush & water mix into the heater core, let it sit for 30 minutes, and then drained. Took off the bottom core hose, and blew air through the core, put the hoses back on, put a new thermostat in, filled with new 50-50 coolant distilled water mix. And now I see no improvement in the heat coming from the heater. The temp gauge goes up to above half-way when the car has run for about 5 minutes on the highway, but there’s very little warmth being kicked out of the heater. Did I get a bad thermostat? Do I need a new rad cap?
The blower motor is kicking out slightly warm air only. All four speeds work on the blower as well. When I set the air selector to “recirculate” (meaning I’m re-using interior air) it doesn’t get any warmer either. I’m thinking maybe the flap in the heater system is not aligning correctly, and letting in too much cold air from the outside, and thereby cooling the heated air from the heater core before it gets into the car.
I took the car for a spin down the highway a couple of miles. Starting off (because the engine was warmed up) I had decent warm air coming out of the heater, but as soon as I got to highway speed (100 kmh) the airflow cooled off considerably. I switched the heater control from HOT to COLD …and the airflow went completely cold. The back to HOT, and the airflow warmed a bit. That tells me the valve in the heater core that controls coolant flow is working properly (right?). Got back from my test drive, and checked the hoses again: top rad hose fairly warm …bottom rad hose still just warmish. What the H**L does that mean? Blocked rad core?? I just flushed it out a week or so back …no indication that it was blocked. ????
Yesterday was a frustrating afternoon. 1. I drained the coolant and took out the new thermostat that I had installed earlier, and did the boiling water trick. It opened fully at 193 degrees. (I put the thermostat in a 1 litre pyrex container of water and microwaved it until the water was boiling. Then I used a digital candy thermometer to measure the temperature.) So, I was able to confirm that the thermostat was working properly. (tested the one I took out …the OEM two-stage type …it was working okay too. $21 wasted there).
2. I put the thermostat back in, and then put the coolant back into the system. Warmed the car up until the cooling fan came on….temp gauge was on the high side of the midrange on the gauge. At that point, the heater was putting out a decent amount of heat (but it was +4C outside!).
3. This time, as I had warmed up the car until the cooling fans came on, the bottom rad hose was hot as well: so, I know the rad is not blocked; the thermostat was functioning properly.
4. I took the car for a spin down the highway again ….and still not very much heat at highway speed. I realize this could partially be a result of the coolant cooling down a bit, but the temp gauge did not move appreciably. But still very weird.
5. As a last resort, I tried the old red-neck winter fix: cardboard in front of the rad. I cut a piece of corrugated cardboard and covered about 90% of the radiator ..cardboard right against the rad. Did the road test again, and surprisingly the output from the heater remained considerably warmer. I know that it was +4C (+39F) yesterday, and that would clearly impact how well the heater worked …so I’m anxious to see if this fix will hold up when it gets down to -35C again.
So …after all this, I still haven’t nailed down the exact cause of this problem …… input please???
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If the engine isn’t overheating then my guess would be that the problem lies in the heater core or the air blend door. I know you flushed the heater core but it may still be restricting coolant flow and may need to be replaced. My only other guess is that your air blend door may be malfunction. I’m not real familiar about how those work but I know it either blocks or directs air to the heater core. Hope that helps.
Plug in the search terms “no heat” into the site search bar up top then go to the FAQ tab.
http://www.ericthecarguy.com/search.asp … at&ff=trueYou’ll see Eric hit a common theme over and over. Either flush the core (which you’ve done multiple times), properly burp the system (unknown), check the blend door, or the heater control module isn’t working.
You’ve flushed the core six ways to Sunday repeatedly but not sure how effective your procedure is for burping the air. With multiple flushes the probability of introducing air into the system is higher I suppose. Definitely give the aptly named “How to Bleed a Coolant System” video a look.
http://www.youtube.com/watch?v=zUpXgAJ1gjUAs for the blend door (flap) and heater control module you’ll need to get in there and do some testing. Remove the glove box so you can see back there and see what the flap is doing while you manipulate the control module. I’m not a 3rd gen owner so I don’t know what is involved to do that. Most cars are the same in that area so you’re likely to get a lot of good advice from others here on that.
You can remove the HVAC module without removing the dash panel in the 3rd gens (1988-1992). I’ve seen some late 1992’s (that people claim are 1992) look like 4th gens. Just because the car manufacturer date stamped on the car says 1992 doesn’t mean it’s a 1992 if the body style is a 4th gen. It actually means it was produced in 92 and sold as a 93 which is a 4th gen. All the directions for repair would be the same but you do have to remove the dash panel in a 4th gen where as you don’t in a 3rd gen. Thought that would be worth mentioning since 92 was a border year before a major platform revision.
-30C is nothing to scoff at. Your life might literally be on the line without heat in Northern Canada. We need to get that heat working for you. Not gonna have a dead 626 owner on my conscience. No sir. You gotta get in there and see if it is that blend door or hvac module.
Not exactly sure what the symptoms are of air in the heater core or coolant system. Maybe someone can elaborate on that?
Okay …sounds like we may be making some progress here!!
1. I have checked the “air blend door” …it is very accessible (right under the glove box area on the far right passenger side under the dash) …it is making very positive contact in both the “open” position (allowing exterior air directly into the fan) and in the “closed” position (drawing interior air into the fan). The door I’m referring to is the one controlled by the dash mounted (and cable controlled) lever labelled INTERIOR/EXTERIOR. Is there another air blend door?
2. I know that the flow through the heater core is not restricted because during one of my several coolant drain and refill procedures, I put a long hose on the bottom heater core outlet, clamped it closed, and then slowly filled the heater core with coolant through the upper hose …then, I put the lower hose in a bucket and unclamped the hose, while blowing through the top hose: the coolant flowed out easily and without too much “lung work” ….so I figured the core was not restricted.
3. I am aware that the cooling system SHOULD be burped, but frankly, I can’t locate a bleeder valve as shown in the video ANYWHERE on the top end of this engine …not back in the area of the injectors (as shown in the video) …and not near the thermostat housing where I thought is would be located (like on Civics, Legends, etc.). There are 4 sensors mounted in the thermostat area: two on the rad side of the thermostat housing, and two on the engine side ….does removing one of these (on the engine side) serve as a bleeder valve?? Is it wrong to expect that the coolant system would “self-burp” after several heat up and cool down sessions? I have been checking the coolant level, and have topped it off several times, but it won’t take any more now.
4. I’m not too sure what removing the HVAC module (which is easily accessible just under the glove box) would accomplish ..?? It is located between the fan housing and the heater box under the center of the dash. Can someone perhaps explain why I’d want to remove the HVAC unit??
5. When you say “heater control module” ..are you referring to the unit on the dash were the heater controls are located, or the unit under the dash where the heater core is locate? I have checked the dash mounted heater controls, and where the cables hook up to the levers and flaps on the unit below, and everything seems to be in place and working normally.
Appreciate the feedback ….please keep it coming.
It sounds like you have air in the system.
Did you put your blower motor on its highest setting along with the heat on full while you were adding coolant, massaging the hoses and bleeding the system of air?
Good suggestion, but as I said, I can’t seem to locate the air bleeder valve on this engine ….any suggestions? I have the Haynes manual which claims to cover the 626 and MX6 from 1983 thru 1992 (my version was printed in 2000) …but it is practically useless in this process. The heater control system (starting at page12-14) is shows bears absolutely no resemblence to the system in my car. (and yes, my car is a 1992 ..not an early 1993 …). Likewise, the section on Cooling, Heating and A/C (starting at page 3-1) talks about changing the coolant, thermostat, etc …but there’s absolutely no mention of bleeding the air from the system after doing so, and of course, no mention of an air bleeder valve. Can anyone post a diagram or photo of where the air bleeder valve is located??? BTW …when it does get real cold here, I DO have a fireplace in the house ….I guess this Haynes Manual may come in handy after all!
Not sure about the bleeder valve. I know the 93-02’s don’t have one. You have to bleed the air through the radiator cap while running the engine at 2k rpm. It’s best to have the front end up on ramps to elevate the radiator cap above the IAC at least for the 4th gen. Not sure about the 3rd gen. I have a 3rd gen 1988 factory manual coming in this week actually. I’ll scan anything you need. As for the radiator cap it couldn’t hurt to pick up another one from the local auto parts store for a couple bucks. Look up the specs for the cap in the Haynes manual. It should at least get that one right. 😉 I’d guess at 13 psi / 0.9bar.
I was talking about the control module yeah. Make sure the control unit isn’t the cause. Switching modes, fan settings, temp settings, etc.. The control module itself can fail especially on the older cars where they use mechanical switches instead of electronic buttons and such.
This video might help. This is what was wrong with my car:
Yes, I have put a new 13 psi rad cap on …didn’t make any difference. The 91 Honda Accord video on Youtube (thanks cb7ftw) was interesting, but its a different set up on the Mazda 626 …the control valve on the Accord is located on the engine-side of the firewall, while that setup on the Mazda is on the inside of the car. I know it is working properly, because when I push the dash lever to COLD, it actually shuts off that valve and cold air is directed into the car …so to me that tells me two things: the coolant flow valve on the heater core is shutting off and turning on …and the “air mix door” in the heater control box seems to be working properly by instantly directing cold air into the cabin when the lever is pushed to COLD. (that Honda system is certainly an improvement: if the valve fails it can be changed without pulling the heater core ….)
The comment from Dreamer35 says I should run the blower fan on HIGH while bleeding the air from the system ….but Eric says to NOT have the blower fan running when doing this (allow more heat to develop, I would guess). I guess I should go with Eric’s method …right??
Thanks for all the input guys ..right now, I going to go with the AIR IN THE SYSTEM theory …and trust that all the mechanical stuff is okay. The weather is still holding pretty mild here for the next couple of days ..and hopefully into the weekend. So I’m going to tackle the air bleed work on Friday afternoon after work.
You can get a spill free funnel from Princess Auto for about $20, and mount that where your rad cap goes, then run the car until the thermostat opens to burp air into the main rad. You’ll see air bubbling out that funnel, but be sure to turn it off before it overflows. I did a video showing that procedure on Youtube titled “mystery of the gurgling heater core” if you are interested. After doing that, if your problem persists, then you know it’s not air trapping and you can move on to other diagnostics.
@djdevon3 Ha ha, you made my day, great post!You dont need a bleeder valve to bleed cooling systems. Just make sure your massaging all the heater and radiator hoses as your adding coolant when the vehicle is warming up. Again with full heat and full blower speed. Also try to raise the RPM of the vehicle also.
Once the coolant level starts to rise, secure the radiator cap and then take it for a spirited drive. Then after the short drive, re check the level and add coolant as necessary to the reservoir.
Good luck!
Might want to let the car cool down before adding coolant after a spirited drive. Even Eric isn’t immune to getting a face full of coolant but steaming hot coolant is something that can change your life. I had a neighbor who burned his face really bad taking a tractor rad cap off while he was working it in the field. Some mistakes follow you for the rest of your life. Let the car cool first. In -30 weather that shouldn’t take too long.
I recall hearing Eric say to flush the heater core with a garden hose both ways to ensure proper dislodge of any foreign stuff. I did that exact same thing to my father in laws car after he took it to his trusty mechanic and right of the bat wanted to charge him 400 bills to fix it. After a lil bit talking to him and gathering evidence, (he loves fixes in a bottle and showed me all the stuff he had bought that claimed to plug leaks and such). I decided to attack the problem. Hooked up the hose and let it run, on both hoses for about 5 min on each. hey it worked. Hope to hear the results.
Don’t forget at the end of the Unclogging A Heater Core video; If you still don’t have heat after trying all the steps, hook everything up, take it out some place safe, and just floor it.
Also a neat video I came across recently thanks ot Spelunkered that might have bearing on spotting recurring air in the heater core issues.
http://www.youtube.com/watch?v=db2nR0EMOIsI agree with most everything here. If the heater core is pretty easy to access, flush it both ways. Then get a spill-free funnel. It’s a Lisle tool, and about 20 bucks. I doubt this applies to a vehicle this age, but if you have a cabin air filter, make sure it’s not clogged. The biggest thing is to make sure you have the heater set to full hot when you are burping the system. I don’t necessarily agree with the fan on high, because if you have more heat in the area, the coolant will expand more, and help pump out air in the system. Other than that, the heater in a car of that era is pretty basic.
YOU DON’T NEED A BLEEDER VALVE TO BLEED THE SYSTEM IT ONLY MAKES IT EASIER TO FILL THE SYSTEM. I should tattoo this on my forehead. Just about everything you describe sounds like air in the system and since you just opened the system you NEED to purge the air out as shown in the video ignoring the bleeder valve portion. What you experienced with the hot and cool radiator hoses is normal as the lower hose is the return from the radiator and SHOULD be cooler. You get points for testing the thermostat the way you did instead of just replacing it as people often do. I’m also proud of you for figuring out that the blend door is operating correctly. I don’t think you have a clogged heater core if you did you would consistently not have heat but the fact that it comes and goes would indicate that you have air in there and I would strongly recommend you rewatch my bleeding a cooling system video and note the annotation about not needing a bleeder valve to bleed the system and do everything else in the video as shown and then recheck for the problem.
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