1997 4runner Heating Issue

[hampston4]

I have a 1997 4runner limited, 4wd. I bought this this truck a little over a year ago, it now has 202,000 miles on the clock. As soon as I bought this runner I converted it to right hand drive to use on a rural postal mail route. I am a substitute carrier so on average I work two days a week, sometimes it is more. My mail route is 70 miles long and it usually takes me 5 hours or so to complete. My 1997 runner has performed beautifully on the mail route, using a car as mail delivery vehicle will usually find any weakness the vehicle has. Expect for the heat, the 1997 has performed beautifully. I noticed last year my heat was not working properly. I flushed the heater core and replaced the radiator cap, seemed to fixed my problem in Nov. 2016. I live in an area where it gets pretty cold in the winter but we had a very mild winter in 2016, so I just know I did not notice any heater issues until a year later in Dec. 2017.

The heat will get pretty hot for a couple of minutes but will gradually cool off the longer the heat is turned on. As long as you keep turning the heat on and off it will keep heating. I want to find what is going on, I like to keep all my vehicles maintained properly, especially my postal delivery vehicle. When I realized that I was once again having issues, I stated with the heater core area. I again went to flush my heater core and noticed that my heater control valve had failed, one of the flanges had almost broken off, I was surprised it was not leaking. I was pumped, that had to be my problem, the failing flange was stopping to the flow to my heater core. Since I had my heater core hoses off I did another flush, it was pretty clean with just a few rust particles. I installed the new heater valve, topped off any coolant I lost, the heat was the same, did not fix my problem. I had bought a thermostat when I purchased the my 1997 because I know the stopping and going on the mail route can cause over heating problems. This truck has never overheated since I have owned it but since I had the thermo on hand I changed it. No change to the heat at all, heat gets hot and will cool off. The heat seems to work better when under acceleration. So I am not sure what is going on. The heater core does not seem to be leaking, the floorboards are not wet.

I did notice something strange yesterday when I was working. When the selector is on heat and the truck is under power, (going up a 3 mile mountain) I heard what I describe as a "crackling" noise coming from behind the center vents. I am pretty that is the area where the heater core should be located. It is not a loud noise but it noticeable once I realized its there. quickly switched the selector to cool and the noise went away. So this noise only occurs when the selector is on heat. That is the only strange thing that I have noticed in regards to this issue.

Summary

Does not over heat - if clogged should have over heated this summer (mail)
Radiator appears to have been replaced in the recent past
Radiator cap replaced last year
Heater core flushed with garden hose (twice)
Coolant is clean
No coolant in the oil
New thermostat


Not sure what is going on, that noise has to have something to do with my problem. I have seen many posts that dealing with similar issues but nothing that mentions the dash noise.

Please help keep a mail man from freezing to death!!!!

Thanks in advance.

 

[jgue467]

I would have flushed with a flushing agent like one from prestone or so.

I would hate finding ANY pieces of rusted material in the coolant, tells you alot about how it was maintained.

Did you turn the rear heater on when flushing? If I'd already flushed twice, I'd consider power flushing it by a pro.

If that doesn't fix it, it's hardware partially clogged up behind the firewall, maybe heater core. Luck. :cowboy:

 

[19963.4lsr5]

If you pull the rad cap off coolant is in rad is touching the bottom of the cap?

That noise you hear In the heater box is air in the system.

Make sure the cable for the heat valve is adjusted correctly. You can turn on the heat with the hood up and watch that valve and make sure it doesn't start drifting closed.

You had to change the heater box to make it right hand drive?


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[hampston4]

Thanks for the quick responses guys. Air in the system was one of things that I was going to look at next. I tried to burp the system last night but I just learned today that truck needs to be slightly elevated in the front to properly burp the system. I will try this before anything else. As far as the heater control valve, it may be moving slightly but I do think so. Lever inside seems to work correctly, I will check this out as well. As far the right hand drive conversion, to my knowledge the only thing that had to be removed was the glove box, it is kind of like a drivers ed. car, you can drive it on both sides.

Since the coolant was fairly clean I did not do full flush, if it had coolant flow problems it would over heat with the 600 stop and goes I do every time I carry the mail. If getting all of the air out of the system does not solve the heat issue I will do a complete flush.

Thanks again

 

[hampston4]

I burped my system today, did not do anything for the heat, still not working properly. I did eliminate the rear heater lines, looping them at the fire wall where the heater core line are. This did not make a difference either. I am going to do the coolant flush tomorrow, hopefully that works. If not it has to be the heater core, right?

 

[nevada]

I burped my system today, did not do anything for the heat, still not working properly. I did eliminate the rear heater lines, looping them at the fire wall where the heater core line are. This did not make a difference either. I am going to do the coolant flush tomorrow, hopefully that works. If not it has to be the heater core, right?

reconnect the rear heater, and use that. it should put a fair amount of heat into the cabin.


once its fully up to temp, check both heater hoses at the firewall. a clogged core will usually give you one HOT hose, and one lukewarm.

changing the heater core is a fairly big job, you may attempt another flush, even a power flush as suggested above before diving into a replacement.

you mentioned you've flushed it already, what exactly did you do? did you use a chemical flush?

 

[Sgtausy]

watch this video

Thanks for the quick responses guys. Air in the system was one of things that I was going to look at next. I tried to burp the system last night but I just learned today that truck needs to be slightly elevated in the front to properly burp the system. I will try this before anything else. As far as the heater control valve, it may be moving slightly but I do think so. Lever inside seems to work correctly, I will check this out as well. As far the right hand drive conversion, to my knowledge the only thing that had to be removed was the glove box, it is kind of like a drivers ed. car, you can drive it on both sides.

Since the coolant was fairly clean I did not do full flush, if it had coolant flow problems it would over heat with the 600 stop and goes I do every time I carry the mail. If getting all of the air out of the system does not solve the heat issue I will do a complete flush.

Thanks again

This is the best video, he goes through each and every step to diagnose the issues https://www.youtube.com/watch?v=-XjXTVJhFLM

 

[19963.4lsr5]

You can back flush the heater core with a air compressor or garden hose. Is do that before a chemical flush.

Was the coolant touching the rad cap when you removed it?


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[hampston4]

Thanks for the responses, still no heat

Update

I did flush the heater core, a little rust came out but not bad.
I did my super flush/chemical today with the thermostat removed, flushed the system 5 times with distilled water and cleaned the coolant res tank. I filled the system with new red 50/50 coolant and burped the system. Unfortunately I still do not have any heat in the 1997. I know for a fact the the system is as clean as a 20 year old vehicle can possibly be. I am not sure what is going on.

I did notice after my flush that the heat my be weaker than it was before I started, its still shitty. The crackling noise that I heard behind the dash vents is gone so I shouldn't have any air in the system now. I did notice that the lower radiator house is very cool to the touch, a lot colder than the top hose. The coolant line going into the heater core is hot and the return line from the heater core is also hot. So I am pretty sure that I am getting hot coolant to and from the heater core. I did also check for a cable malfunction from the blender under the dash, I took it lose and it seemed to be moving fully in both directions. No adjustment needed.

The only thing that I can come up with, is something under the dash is not working like it is supposed to. Something is not causing the hot air to blow over the heater core. Is there 2 fans, 1. the blower fan and 2. a fan that blows air over the heater core. I have not had a chance to look this information up yet. But it has to be something under the dash...

New thermostat
Coolant super flush
Heater core flush
Checked for play in the blender
New Red Coolant

I would hook up the rear heat but a previous owner has removed the entire rear heat system.

Thanks again

 

[phattyduck]

I did notice that the lower radiator house is very cool to the touch, a lot colder than the top hose. The coolant line going into the heater core is hot and the return line from the heater core is also hot. So I am pretty sure that I am getting hot coolant to and from the heater core. I did also check for a cable malfunction from the blender under the dash, I took it lose and it seemed to be moving fully in both directions. No adjustment needed.

The only thing that I can come up with, is something under the dash is not working like it is supposed to. Something is not causing the hot air to blow over the heater core. Is there 2 fans, 1. the blower fan and 2. a fan that blows air over the heater core. I have not had a chance to look this information up yet. But it has to be something under the dash...

Thanks again

Too bad the rear head system is gone. It is 100% mechanical, so no worries about the Limited digital controls malfunctioning.

The top radiator hose is the outlet from the motor and should be hot (engine operating temp). The lower hose is the 'cold' coolant inlet to the motor, so that is working well.

There is only one fan that runs the HVAC system. How is the airflow? Do the blend control work to send air where you want it to go? Can you watch the heater valve in the engine bay change positions when you request heat vs not?

Another thought - how does the AC work? Keep in mind that the AC compressor runs when mode is set to either defrost setting. A good working heater should be able to overcome that and reheat the air to a good temp before it blows out the vents, so that may be barking up the wrong tree.

-Charlie

 

[Kanoe]

I would hook up the rear heat but a previous owner has removed the entire rear heat system.

The previous owner didn't remove the rear heat by simply looping in and out with a hose did they? If they did, you have a 6 inch 'path of least resistance' bypassing your heater core, allowing at least a portion of your hot coolant to bypass.

Just a thought. I did this on mine initially and found the heat to work better once I found proper caps to terminate the old rear heat taps. I have fully ripped the rear system out of mine too.

Good luck.

 

[hampston4]

The A/C compressor kicks on when the button is pressed. The A/C did work when I purchased the truck in Sep. of 2016 but the freon must have leaked out. It does not work anymore but that shouldn't effect the heat, should it? They did but I did the elimination that I read about on here, cannot remember who did the original post. It loops at the heater core, I basically eliminated the entire rear heating system.


Keep the info coming!

 

[19963.4lsr5]

I have my rear heat bypassed up at the control valve and no decrease in heat


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[Kanoe]

I have my rear heat bypassed up at the control valve and no decrease in heat


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But would you if you had a sub-par heater core? I would suspect so...

Just offering suggestions.

 

[hampston4]

I have learned that the front and rear heat use different systems. The rear heat will work when the front will not. Front will work without out the rear. They share the same coolant, that is all.

 

[hampston4]

As far as I can tell my 1997 has all mechanical heater and A/C controls, even though it is a Limited.

 

[Kanoe]

I have learned that the front and rear heat use different systems. The rear heat will work when the front will not. Front will work without out the rear. They share the same coolant, that is all.

They are actually parallel systems. The rear heat taps off just before the heater valve for your front heater. Then the rear heat system returns into the hose coming out of your front heater core.

So not entirely different systems. There is one hose carrying hot water from the engine which feeds both systems and then it combines to return to the engine in one hose.

Hope you fix it.

 

[diverscale]

Flush is often not enough (never in my case) to unclog a heater core. I use CLR, taking off the two heater hoses, putting them in a ''up'' position (to retain liquid into heater core), blow air in the lines to remove coolant, then put the CLR in. Let it soak 1-2 hours (yes) then backflush with a hose garden. Finally blow air to get water out, plug everything back, and bleed system.

 

[thegipper]

Flush is often not enough (never in my case) to unclog a heater core. I use CLR, taking off the two heater hoses, putting them in a ''up'' position (to retain liquid into heater core), blow air in the lines to remove coolant, then put the CLR in. Let it soak 1-2 hours (yes) then backflush with a hose garden. Finally blow air to get water out, plug everything back, and bleed system.

I would try this next. Just be super careful blowing air into the heater core, they can rupture if you put in too much pressure then you will have to replace the heater core (although you may end up having to replace it anyways).

If the heater hose that goes to the heater core feels hot after it is warmed up and the heater controls are working properly, it has to be bad heater core.

 

[19963.4lsr5]

My little 2002 Saturn had a clogged heater core when I bought it. I reverse blew it out and got some nasty crunchies out of it. Did it 3 times until it was clean reverse blowing it. My brothers Saturn was the same way. Back blowing his heater core had black junk come out.


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