Losing my MIND. NO HEAT DEAD OF WINTER
 

Hello ladies and gentlmen. I am experiencing an issue with my heat not wanting to function properly. I'll go over the steps I've already taken to try and solve the problem here. Along with other odd things that have happened during the process. So initially I replaced the thermostat, naturally thinking that it had failed and been stuck open. Nope. Next I removed radio, glovebox, vent portion under radio to access heater core. Feed side into core gets pretty hot (usually, but I'll get into that), return side is much cooler. So what did I do? I removed the hoses from the fire wall under the hood and fed water through. seemed to flow ok. Next I removed hoses from the core itself and blew compressed air and water through. Bunch of gunk came out and I thought thank God, problem solved. Nope. Lastly, I noticed my cooling fan is constantly running, from startup, onward. So I thought oh ok, not allowing coolant to reach temp, duh. Nope. And this is what leads me to the weirdest part. I restricted airflow through the radiator using cardboard and on my way to work temp gauge went red alert and was reading that I was overheating. So you'd think the core would be burning up and air would be hot as hell? Nope. Air was not hot at all rather it was ICE COLD. I am just at my wits end here and maybe I'm overlooking something and it's easy fix, but I need more people' opinions on this and ideas also. I thought for sure it was the cooling fan because on warmer days the core gets hotter and the air is warmer. Colder days I have very little luck. I just want this resolved because no heat freakin suxks. Also if anyone could think of an alternative source of heat that would be great lol. I forgot to mention radiator hoses are not getting as hot as they should be and they don't feel full like they should. Coolant resivoir is full also.... It could be damn near anything. But I don' want to go wasting money and just throwing parts at the old girl. So please help me!!!!!!

Have you checked your heater control valve? It has to open in order to get water flowing through the heater core. The normal flow of water comes out of the engine block through the heater core and back to the line that runs to the water pump. Any blockage along that route would cause no heat.

Id start taking stuff off one at a time and see whats plugged. The radiator and heater core could be plugged.

both heater hoses are hot, yet the heater core isn't hot? is the fan blowing air past it ?

are you sure the heater valve is working? is this a 240 or 7/940, and what year ? many 240's had a thermostat based heater valve thats prone to failure.

sounds like you might have an air pocket in there somewhere and the system needs
to be 'burped'.

I hear ya...I've been there before, though in my case, it was just lukewarm air, not ice cold.

From your (admittedly thorough) troubleshooting, it sounds like coolant isn't circulating. Could be a few issues:
- Could be an air pocket right around the water pump...just need to rid the system of air
- Could be a bad water pump or belt slipping

Good luck!

Thank you! How would I go about unclogging the radiator if it is indeed clogged? I may have another go at the heater core to remove anything else, but I did blow water and compressed air through it and lots of gunk came out.

yes I'm fairly certain! it is a 92 240! The heater core gets warm/hot with the plenum to the outside air closed, but depending on how warm/hot it is when I open the plenum it cools fairly rapidly. I think im really just having an issue with the entire cooling system itself not getting the coolant hot enough or I have air in my system, which I really don't know how I'm supposed to get out with the way the coolant system is set up with no radiator cap and only the cap on the reservoir. I'm thinking I may remove the water pump to check out it's condition because it does look fairly old and if stuff I blew out of the core is inside the pump as well I could be having flow issues. any ideas are greatly appreciated! thank you!

Thanks for the suggestions! it sure feels like I have air in the system.. based on what the hoses feel like at operating temp. But how can I go about getting them out? How can I get rid of ALL the air? it's so much easier to do on vehicles that actually have radiator caps.. I'm having a hard time with its current setup. The reservoir setup. idk maybe I'm doing something wrong. I think I should pressure test the system and see if it' sucking air from somewhere because until I know for sure the system is leak free I'll just be wasting my time.

Im thinking that could definitely be part of the problem... What is really stumping me is why when the temp gauge reads overheating the air comes out ICE COLD. Unless maybe you think that all the air when it's hot ends up in the core due to the pressure in the system? I guess that's a possibility. I just hate the cold and with two kids it' hard to find the time to get out there and work on her before night time comes and I'm off to work in an ice bucket!

It actually makes perfect sense to me...If the engine is overheating, and there is no coolant flow, the heater core won't absorb any heat. The coolant will just sit there, and will not heat up. The engine will overheat because there's no cooling going on!

To "burb" the system, you can do the following:
1. Make sure your coolant tank is full, slightly past the max mark, and your cap is off. Keep your car idling. Turn your heater to hot, but you don't need to turn the fan on.
2. Using the upper coolant hose, consistently pump/squeeze it, slowly...enough until you feel the hose getting warm/hot. You should also start to feel the upper part of your radiator getting warm.
3. Feel the coolant pipe near the inlet of the water pump. It should be warm, not cold.

If the lower coolant hose is consistently warm when you're not pumping the hose, then that means you have coolant flow. If its cold, then think about changing your water pump.

So I removed the top hose from the thermostat housing and loosened the clamp on the radiator side so that I could turn it upwards. I then clamped a funnel onto the thermostat side of the houe and filled that with coolant while squeezing the lower hose to ensure the radiator was full. when it reached its max I replaced the hose and started the car and continued squeezing. finally the hoses felt like they were full and didn' have air in them. I took the car for a test drive and was having more luck with the heat, but I think there is a small bit of air still in the system or I have a flow issue. Either a clog or poor pressure from the pump. The control valve has a small leak if I press to hard right towards heat on the mechanical switch so I may order that part and bypass it for the meantime. ALSO. I need to replace the fan clutch because it's shot and it's constantly spinning and pulling air through the radiator. It's a work in progress. lol But I'll keep you guys updated! thanks all!

Here's another idea: cover half the radiator with cardboard and drive around. See if that helps anything...

Already ahead of you! Now I didn't know the intake manifold trick, but the fan clutch is spent. I did do the old glove method, but with confidence because I knew the fan clutch was already burnt up. as for the cardboard trick, I have one in there now to restrict flow and it does seem to be helping. When I still had air in the system though it did cause the needle to go red and that's where I thought the cold air coming from the vents was really odd until I figured out the core was probably just full of air. with the cardboard and the system almost air tight I was getting better heat than I have been since the issue first began. we shall see though on one of these next really really cold days. Keep you posted

So is your fan clutch ALWAYS engaged, or NEVER engaged?

These clutches are fluid clutches so they'll never "burn up". Its more likely they will lose fluid and seize, permanently engaging the fan.

yea it's always engaged. I didn' mean literally burnt up, but it's always engaged so I think that's definitely part of the problem. Just drove it to my brothers house and it reached "operating temp" and I checked the intake mani when I got out and it was barely warm :(