Heater woes (1 Viewer)

[robertaleon]

Sorry to bug ya'll but getting towards my witt's end. I have a combo of heating issues and trying get it all figured out.

1995 FZJ80 with 258K miles, and OEM tstat installed correctly with jiggle valve facing up (see sig for other details) has officially turned into family ski rig, mainly because it is extremely capable in snow and already has bumps and bruises and people at ski resorts are notoriously jerks when it comes to banging into rigs with their boards and ski stuff.

This season I've noticed that the heater does not get warm very easily, usually once the engine/coolant temp reaches 185F on the Ultragauge. Usually in the winter driving in Sacramento my engine temps hardly ever get above 180F and in Sacramento, I don't need heat for the cabin. The rear heater works fine , very hot 140F air coming from there. It has been about 3 years since my last coolant flush and fill so I decided to give that a try. I also went ahead and tried the reverse flush of the heater core to clean out any garbage in the heater core. I got good reverse flow from the core and a medium amount of debris but nothing extraordinarily. The coolant I used in the past had been Prestone Green so this time I decided to go Toyota Red. Did two flushes with tstat out, 1 with about 100 miles of driving, and the other 1 hr idling in the driveway. I filled the system with Toyota Red, put the front on ramps and attempted to burp the system like I had in the past. Yesterday the family drove up to go skiing and had plenty of heat in the valley but lost hot air going up the mountains. Engine temps were between 176-199F at times. Everytime the engine temp got warm from speedy climbs, engine temps would fall below 185F. I also have a pair of large Hella 4000 up front which typically restrict airflow in the summer but seem to have little affect with engine temps in winter. During our travel home we needed the defroster so I pressed the AC button and the windscreen defrost button (both lights illuminated) like normal. At this point the little bit of heat I was getting was now replaced by nice cold air, as if the heater was not even on. I performed some more tests with vent at face, feet, combo, etc. and found that no matter the venting, the AC always blows cold air. Once returning to the valley, I performed another test and found when AC button is engaged, I only get cold air - regardless of the temperature slider. Turn the AC button off and slider all the way hot and engine temp above 185F - nice and hot. After 150 miles any air may be out of the system but confused on the AC/No AC thing..

In summary:

1. OEM t-stat
2. Recent flush
3. Fresh Toyota Red coolant (nearly 3 gallons including reservoir
4. No heat until engine temp reads 185F
   1. May be completely burped at this point after last trip to mountains
5. Rear heat always hot
6. AC button engaged and slider on hot, blows cold air
7. AC button disengaged and slider on hot, blows warm air.

Help always appreciated

 

[Kaninja]

Heater core failing / partly clogged?

 

[rolliges]

Does the HVAC fan push air? is it quiet or not? Do you have an ambient air sensor (lower left face of controls)? If so, clean that out.

 

[amgraham]

I'm assuming you checked to make sure the system is still full after you lost heat. If so, you most likely have a blockage somewhere. Run it with the heat on at operating temp and check your heater hoses. If they're hot some places and cold others then you should be able to zero in on the blockage. Especially if it's not going into the front heater core and cold coming out.

Also, I'll go ahead and say it was probably a bad call switching back to red coolant. It sounds like you flushed it enough but if there was any green left in the system and it mixed with the red it's pretty common to create sludge. Not saying that's your problem, but it is another variable.

 

[robertaleon]

@Kaninja: As mentioned - backflush on heater core performed and good flow in both directions.

@rolliges - it’s a 95 and I do have the little openings at bottom left of controls and will clean those out. Fan moves air volume pretty good and volume improves with the recycle button.

@amgraham - yes, stated system full - 3 gallons including reservoir and remains above low line in overflow. Heater hoses all hot during operation; both sides of heater control valve, in/out from heater core are hot, and upper and lower radiator Hoses are both hot. I’m confident in my flushing process and burping attempts that I’m not concerned switching to red from green. As many have stated with experience, so long as flush is thorough, it shouldn’t matter.

My two questions remain for those that either have a scan gauge or ultra gauge :

1. Do you all only get heat once truck reaches ~ 185F?
2. Anyone ever experience and resolve the issue of AC blowing cold regardless of temp selection (cold whether slid to hot or cold)? Again- I can get heat if truck is hot enough but if I hit the AC button for anything , I start getting cold air.

 

[JTU]

Have you tried disconnecting the heater control valve from the linkage and manually opening it? If you manually open it and still no hot air it’s probably either your heater core or the flapper door is not opening all the way.

 

[amgraham]

Gotcha.

1 - I too have an ultragauge and have just recently worked through my own heat issues. My coolant temp seems to fluctuate between 179 to 190 depending on load, ambient temp, etc. I most often see 185 ish and I start feeling heat around 120ish. I have full heat at the 179 and I guess it is slightly hotter at the upper end but it is definitely ample at 179 (like, crack a window unless I turn down the temp slider). My rear heat is bypassed.

2 - If you have no heat to counteract the A/C it will blow cold. The A/C system is essentially either on or off and the temp is regulated by adding heat. The only real reason to run the A/C with the heat is for the dehumidifying function. Fix the heat issue and the A/C "issue" should resolve itself.

 

[cahill]

Have you tried disconnecting the heater control valve from the linkage and manually opening it? If you manually open it and still no hot air it’s probably either your heater core or the flapper door is not opening all the way.

I agree with @JTU . Taking a look at the heater control valve is a good place to start. Have someone in the cab move the temp slider from all the way cool to all the way hot and see how much it actually moves the heater control valve in the engine bay. You could then disconnect it in the bay and move it yourself further towards hot/open and see how much more play there is and if you need to adjust the cable.

 

[450LX]

Yeah double check the heater control valve and I would try some evaporust too. Put the evaporust in your cooling system with water and let it sit in there for atleast a week starting it periodically. Dont do it if it's going to be freezing out, obviously. This stuff works wonders and will probably clean out that heater core better than anything else. Worth a shot, the heater core is a BIT$H!

 

[rolliges]

I get heat with the engine starting around 120F. Thermostat opens around 180-184F. My heater gets as hot as I want.

Had a neglected system: flushed 5+ times until clear for a few days (block, heater core, everything); new heater valve, new rad. Works like it should. There are only so many variables.

 

[Squash]

Heater control valve and open rad cap to visually inspect and verify that rad is full.
Overflow means nothing till you ensure a full rad.

 

[bigredmachine]

sounds like either an issue with the heater control valve, front heater core or the blend door in the blower box. depending on age and how it looks you may just want to replace the heater control valve anyways as the plastic can get brittle

 

[Fj81]

@NLXTACY aka wits end

 

[Cruzerman]

So the rear heat works but not the front? And there is no blockage in the front core? To me, this means it is not the heater control valve (rear works). And since the front core basically Ys off right at the firewall, so the same hot water that is feeding the rear (which works) is feeding the front (that doesn't work). Since we're confirmed no blockage, to me there must then be hot water flowing through the front core, but no appreciable heat coming out.

Either the blend door / flapper is not working or the heater core fins are clogged up the hair and stuff. I'm thinking the blend door, only because mine does the same thing and I know it is the blend door since it sometimes works great and other times gives no heat. Try playing with the hot / cold lever a bunch. Sometimes it's a dirty rheostat or bad solder joint on this board. Otherwise, you're going to have to dive deeper into the dash. JMHO.

Good luck.

 

[robertaleon]

@Squash - yea , rad tank full, checked checked, and rechecked .

Also as someone asked - this was 50/50 mix.

 

[Squash]

Good luck!
You've done the easy stuff, now the work begins.

 

[rolliges]

Just for kicks find your hamster wheel and clean it.

 

[Squash]

Don't know if you tried this but check hoses for heat/flow going in and returning. Worst case is you could try bypassing the valve.