- This topic has 60 replies, 13 voices, and was last updated 12 years, 11 months ago by
.
-
Topic
-
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???
-
Replies
-
10:49 PM (local time)
Some exciting progress to report …but not complete success (yet). Got the car into my new-found heated workspace, and then had to let it cool down before I could work on it. Drained the coolant. Elevated the front end about 4 inches. I had found some lengths of heat core hose the same size as those on the 626 …so I removed both heater core hoses and attached a two foot piece of hose to inlet and one to the outlet on the heater core. Clamped off the bottom hose, and using a funnel on the top hose, I filled the core with straight CLR. Let it sit for 20 minutes, then drained it out the bottom hose. Did this 3 times with the same CLR (strained it each time). A fair bit cruddy grit came out with the CLR. Then I filled the core with clean water …blew it out with air pressure ….three times as well. More fine grit came out, but not much at all. I put the old two-stage thermostat back in …and replaced the upper and lower rad hoses with new ones. Strained the old (new three weeks ago) coolant and added it back into the system. Removed the cardboard from in front of the rad. Then, I did the air-burp process with the special funnel: revved the engine up to 2500 rpm ..left the heater fan off ..but the heat lever all the open (to allow coolant to flow through the heater core. Waited till the cooling can came on. A fair amount of small air bubbles were released into the funnel …massaged all the rad and heater hoses. Repeated this process FOUR times over about a 4 hour period.. Third time ..a LOT of air was released! I was totally amazed! No idea where it came from!!.. Fourth time, only a few tiny bubbles of air were released. During the third and fourth burping session, I was starting to get some decent heat from the heater. And after the fourth session, there was almost “acceptable” heat being produced. Took the car for a 20 mile run at about 70 mph .(revving at about 2600 rpm)..and was getting decent heat. However, when I pulled back into my driveway, and let the car idle for a few minutes, although the temp gauge still showed higher than middle temp, the air coming out of the heater was almost “cool” ….revved it back up to 3500- 4000 …and got decent heat again.???? New problem? or still air in the system???
I see one of 2 things happening here, something in the system might be creating an air pocket like a combustion leak somewhere OR you have a restriction in the heater core. I put flow through the water pump very low on the list, if the water pump wasn’t putting out I would think the engine would be overheating.
Thanks for chiming in, Eric. When I was doing the core cleaning, there wasn’t much resistance when blowing air through the heater core: I could blow through it (mouth on hose) without much effort at all …didn’t do a “before and after” test, but after the cleaning, it didn’t seem to be restricted. Took the car for 150km run yesterday, and it seems to have settled in a bit: still getting a fair amount of warmth coming out of the system, even at idle. Perhaps the engine is continuing to expel small amounts of air into the overflow tank …and that may be the reason for it getting better.
If I have to open up the system again, I think I’ll do another core flush, and replace the heater core hoses (just in case there’s a pin-hole leak somewhere) and perhaps put the new, single-stage thermostat in again. But I think I’ll call it a “success” to point.
Now that I have an indoor, heated space to work it, I’m not feeling so panicked about the rest of the winter. It was -14C yesterday, but up to 0 C today (32F) and the forecast is for minus mid-teen C temps for the rest of the month ….But I know from experience that the -40C stuff will show up in January and Feb. !!!
Thanks again for all the input and suggestions from forum members! You guys are awesome!!!
Great to hear. Sounds like you’re on the path to heat. I had no idea air in the cooling system could be such a pain. I’ve learned a lot from your issue Digger. Thanks for continually updating us it’s good stuff. Do you still need part of the rad blocked off for all of this or are you now able to run without it?
Keep in mind that the core can be restricted and still have flow through it, it’s like a radiator in that there are many passages in it so some can be plugged and others can be clear. With a situation like this you would get ‘partial’ heat because you are only using half of the heater core.
Quoted From EricTheCarGuy:
Keep in mind that the core can be restricted and still have flow through it, it’s like a radiator in that there are many passages in it so some can be plugged and others can be clear. With a situation like this you would get ‘partial’ heat because you are only using half of the heater core.
Well …my worst fears have been realized: it has now gotten considerably colder, and the heat output has been reduced to virtually nil !!! Crap!!
We have been having a very mild winter here on the Canadian prairies …daytime temps in the -5C to +3C or higher range since early December. The coldest its been is about -15C overnite. ….and the heater has been putting out acceptable levels of heat.
Well, yesterday and today, the temp has been -28C during the daytime (-18F) with windchills in the -47C range (-52F) range. You can imagine what the windchill might be while driving 100 kmph down the highway!!!
Even though the temp guage gets up to the “normal” range ….there is almost no heat from the heater at highway speeds, and almost acceptable heat when sitting at idle for a few minutes.
Am I still dealing with air in the system here, or do I have another problem??? I’m putting the cardboard in front of the rad again tomorrow, in hopes of keeping the heat level up while driving on the highway …
Thanks for the reply, however we’ve plowed this ground before: yes…it is the OEM dual stage thermostat; I removed it and tested it …tested out okay using the near boiling boiliing water and a candy thermometer . As I noted, the temp guage is showing normal to slightly above temp. I ran about 60 miles this morning (-29C ) with the rad about three-quarters covered, and I was able get enough warmth to keep the windows clear in the inside, and take my gloves off. I’m going to do a complete rad cardboard job on it before I head home tonite and see what difference that makes.
It still would be interesting to see what the actual temperature of the coolant is via scan tool data when you have no heat.
Are you losing coolant anywhere? Either through a leak, which would be obvious by this point, or a head gasket leak? I had an older Taurus that had a head gasket issue. It wasn’t so sever that it would overheat, but it would use up a gallon every 2-3 months. I hadn’t noticed you mentioning whether or not you were adding any, but it may be hard to tell since you have to continually drain and fill the system.. Also, what Eric said about half the core being plugged seems very reasonable.
I’m not a fan of putting cardboard in front of the radiator besides if your engine is getting up to temp this will do nothing to help with your heat. That said you may still have air in the system, you really need to follow the bleeding procedure to purge any air you really can’t rely on it to get better on it’s own. The sure way to know if it’s a restriction in the heater core or not is to feel the hoses going into the firewall when the engine is at operating temp, if both hoses are hot or warm then you know you have flow through the core, if one hose is hot and the other cold or luke warm then you can conclude there isn’t proper flow through the core. If both hoses are hot and you still don’t have heat the issue is with the HVAC likely to be the ‘blend door’ that switches between hot and cold air in the HVAC. My bets are on the core being restricted but do the tests and confirm the source of the problem.
Okay. ..this is getting bizarre again!
It’s milder here again …only -5C for the last number of days, so I’ve removed the cardboard from in front of the rad.
Coolant level when cold or hot, remains constant in the expansion / overflow tank ..its at the HIGH level as recommended in the manual, and has not varied since I did the major burp session a month or so back.
Temp gauge gets up to about 1/8th inch higher than middle of the scale between C and H. This has not varied, and does the same with cardboard in front of the rad.
Checked all the operations of the control cables: wherever I set the controls to, that’s where the air flows, so I assume they are working correctly.
At this ambient outside temperature, I’m getting good heating in the car: warms up to operating temp (as above) in less than 2 kms.
I drove 25 kms this morning …stopped and checked the hoses: both heater core hoses hot (too hot to hold onto with bare hands); top rad hose, hot; bottom rad hose, COLD !!!
SO, WHY DO I HAVE A COLD LOWER RAD HOSE AGAIN???? More air in the system???One of your radiator hoses will be cooler than the other depending on the coolant circulation flow.
(I am going to go on the assumption you understand how the cooling system works and how the radiator acts like a heat exchanger?)
Out of curiosity, what ratio of antifreeze and water do you have?
There should be some change however in the level of coolant over flow in the reservoir. Obviously fluids will expand when heated.
- You must be logged in to reply to this topic.