pungojoe

• I've had this 4trunner for 15 years and it never had the best heat but it did work enough to keep it semi-warm inside. I installed some aftermarket heated seats which made it comfortable enough for the Maryland winters. Over the years the heat has been getting worse. I have flushed the cooling system several times over the years and it was always clean. It now has 188k miles and still runs great. It's a limited with a 3
• On a long trip this winter, the engine overheated and I was able to catch it in time without any damage. I diagnosed it to a partially clogged original radiator. Before changing the radiator, I did a chemical flush and it did have some particulates come out but not too much. I keept draining from the passenger side of the block and bottom radiator hose. Final flush was with several gallons of distilled water.
• While I had the cooling system open, I used a fluid pump connected to the heater core and a 5 gallon buck with some CLR and water to keep circulating the cleaner. I back flushed and forward flushed several times for over an hour and had very good flow through the heater core. Some particulates came out though not a huge amount. I attempted this flushing on for the rear heater core, but the pipe running down the firewall sprung a leak, so for now, I just plugged capped them off.
• Check the heater core water valve and it has good flow and the cable is adjusted properly.
• Installed a new Toyota thermostat with the jiggle valve at 6:00
• Installed the new radiator and filled the system with Toyota coolant diluted with 50% distilled water.
• With a Lisle radiator funnel and the front of the vehicle on uphill on a steep incline I burped the system by reving the engine and squeezing all the hoses. I think I was able to get all the air out. I then topped of the overflow and put a new cap on the radiator.
• I now have heat, super happy, not really hot heat, but it works better than ever. So the next few days the heat gets less and less until it is putting out air colder than my skin, so not good.
• I'm thinking the heater core needs to be replace even though it had good flow when I cleaned it. So went through the trouble to replace the heat core. It's a pain and took 6 solid hours. I took the seats out which made it much easier. I also thought that maybe one of the blend doors inside the heater box was not working so with the heater core out, I could clearly see that both blend doors for the heater core operated properly. After putting it all back together and burping the system like I did previously still no heat! Really pissed now.
• If I leave the hvac blower off for a while then turn it on, I get heat for 30 seconds or so then it blows cold. I get no heat when stopped or on the highway. I'm getting ready to throw in the towel. I been wrenching for 45 years and have never not been able to figure out a problem. This has really got me stumped. Only thing I can think of is there's a restriction for the flow coming from the block for heater core or the return into block from the heater core? I blew into these inlet and outlets and there wasn't any restrictions though maybe there's some kinda clog in the block? When I feel the hoses at the heater core on the firewall, they are both hot, so there has to be some flow, I just don't know how much.
• If I can't get the heat working before the end of summer, I'm going to have to sell the vehicle since I use it for my winter beater here in Maryland and there's not any heat to keep ice and snow from building up on the windshield, besides freezing my a$$ off all winter really sucks.
• Someone please give me some ideas since I tried everything I could think of.
• Here's what I've recently done:
  • Timing belt, water pump and coolant hoses using all Toyota parts
  • Replaced radiator and heater core
  • Replaced thermostat with Toyota brand, jiggle valve at 6:00
  • Checked heater core water valve and properly adjusted cable
  • Checked heater blend doors and cables, adjusted properly
  • Chemical flushed entire cooling system
  • New Toyota coolant
  • Front end up in the air, burped radiator using Lisle funnel, several times weeks apart (highly recommend this funnel)
  • Installed new radiator cap
  • OBD II reader shows coolant temp in the 185-195 degrees
  • Temp gauge in the middle
  • Cooling system holds pressure, hoses are firm when hot. meaning the cap is working
  • No leaks, never have to add coolant
  • Overflow reservoir filled to proper level

75w90mantraN

Fan clutch check...
Does fan ever come on?
195 is still cool/just warming up. Does it ever go higher?
Engine coolant temp sensor/wiring check

pungojoe

Fan is always on, it's mechanical. if there were a problem with the fan clutch, wouldn't it have an overheating problem, not lack of heater core heat?

I though with the stock 180 degree thermostat, 195 would be normal, it always stays below 200, it is winter after all, so it may go up more with warmer weather. What temperature would be normal if 195 is still cool? I would think 195 degree coolant would be hot enough to at least get some warm air coming out of the heater? My chevy truck stays below 200 in the winter and puts out a ton of heat.

If the engine coolant temp sensor/wiring is sending a good signal to the OBD II reader, then doesn't thar prove the wiring and sensor are working properly?
AFAIK, the temp sensor or wiring will have no effect on the operation of the cooling system or would effect the ability for the heat to work in the vehicle. I thought the obd temp sensor would only effect the computer for emission purposes.

old87yota

You should get plenty of heat at 195°F.

The heater system on these 4Runners is pretty basic, or so we thought.....

I assume the line you capped off was only for the rear heater, right?

Does the cable that is supposed to open the water valve move the valve open and closed fully?

Does the valve physically move open and closed (as in remove heater hoses and look at the inside of the valve)?

Are you 100% sure there is no air in the heater core?

Is there a lot of debris in the A/C or heater box under the dash?

What is the ambient outdoor temperature?

I am just trying to find a reason for the heater hoses to be hot but you are still not getting any heat. You seem to have done a pretty through job!

There is a reason you don't have heat. We just need to find it.

pungojoe

Yes, I only capped off the small ports where the hoses go for the rear heater.

I removed the valve and checked the operation to see that it opens fully as I looked through it. I installed it and operated the lever for the cable and verified it fully opened it as I can see clear through it with the hoses off.

I'm not positive there is no air in the heater core, but I parked on a steep incline with the front uphill and use a Lisle Funnel that attaches to the radiator filler neck while it had 4 inches of coolant in it above the filler neck. Reved the engine many times squeezed hoses. I repeated this a few times over a few weeks so I hope that would have gotten any air out of the heater core.

These is zero debris in the a/c or heater box, I removed the heater box from the vehicle when I replaced the heater core so I could operate the blend doors to make sure they were opening and closing properly to direct the air through the heater core.

Outdoor temps have been from the teens into the 40s and it only put out heat for 30 seconds or so when I put the blower on then it blows cold.

I've really done everything I can think so I'm open to any additional suggestions to get this working. I already started keeping my eye out for a used winter ride, which I really don't want to do, I want to fix this and not let it defeat me!!!

75w90mantraN

Just covering bases since a lot of things were done to fix a seemingly frustrating problem.

You must be in a cold place this time of yr...

200 would be more like op temp. For some makes, the fan doesnt engage until after 210.

All the heater hoses checked for restriction? New heater core is Toyota too right?

You said you verified the blend doors...how exactly? Is it possible something is partially obstructing the cable mechanism or seized/worn?

Funny it's mentioned that flushes were part of routine service but then the rad became blocked...some things aren't quite as they seem.

I would suspect the blend doors, a restriction, or a leak somewhere, even though you mention that you verified. Please dont take offense as some here do. Its just difficult to try and help when we're physically unable to see it for ourselves.

75w90mantraN

Did you run the heater on full blast while burping out the air pockets? Not mentioned and worth clearing up.

pungojoe

No offense taken, any suggestions are welcome.

I check both inlet and outlet heater hose by blowing into them and there was zero restrictions. The heater core is Toyota.

I bought the vehicle with ~90k miles on it over 15 years ago, so I don't know the history of flushes prior to that. I use it mostly for shorter trips, but I was on the highway doing 70+ mph for ew hours, so it must have caused some particulates to come loose and clog up the radiator. Looking the my flush history, I never went past 4 years without a flush, and several of those were not a flush but a drain and fill since there fluid was clean. Maybe I should have performed more chemical flushes?

The blend doors were easy to see operate properly when I had the heater box out. Both doors are connected with a rod so they work in unison. The cable operates freely and moves the door. I check the cable adjustment per the manual. I did allot of checking of cable operation prior to replacing the heater core since that's what I was hoping the problem was since removing the heater core was not trivial.

pungojoe

I had the coolant control value on full hot (lever toward red). I had the heater fan on but not full blast. I'm not sure how the fan speed would aid in removing air from the heater core, but maybe I'm missing how this would help?

75w90mantraN

I run mine on high, but I dont see anywhere how fan speed relates to ridding out air.

My guess is with using strong solvents, maybe more crud got loosened up over the recent drive cycles and stuck somewhere in the lines.

Thinking out in Jupiter, maybe the AC is on somehow, like shorted ON. Compressor isnt running hopefully...

Malcolm99

Have you removed the blower motor to see the blend air doors are moving properly to divert air to heater core or bypass, does your HVAC controls have the slider control or the dials.

pungojoe

With the blower motor out, there is no way to see the blend doors since the a/c evaporator is between the blower motor and the blend doors so the evaporator completely blocks access to see the blend doors.
When I replaced the heater core, I had the entire heater box out, tested and verified the operation of the blend doors while I had it on the bench with the new heater core install. The blend door are operating perfectly.

I have the slide controls not the dials, I verified the slide lever operates the blend doors and coolant control valve properly. I adjusted both cables per the shop manual and verified for smooth and easy operation.

I even used a bore scope down the center air vent to watch the operation of the blend door, which it opened and closed properly when moving the hot/cold slide control.

Not sure if some crud loosened up and stuck in the line, but when I blew into the inlet and outlet hoses coming from the engine block to the heater core, there was no resistance and the fluid in the radiator raised when I blew into them.

The A/C compressor is definitely not coming on.

fierohink

pungojoe

The coolant is full as I check the level each time I burped the system to make sure all the air was out.

Was your coolant level low when your HG went?

fierohink