Any Toyota Techs on here?

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moparker

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I have 99 4Runner that has me stumped. I have problems with the heat. I have replaced the thermostat, heater control valve and heater core. I have checked the blend doors. It comes up to temp fine, does not overheat and, its not losing coolant. It blows hot at higher RPMs or while driving. Come to a stop and blows luke warm the same at idle. The only thing left is the waterpump. Just not convinced that its the waterpump. Any help would be appreciated.
 
Can you see any of the blend door linkage? If you can confirm that the doors work fine at RPM but they recess at idle, you may have a vacuum problem. I cannot remember that far back if the HVAC system is vacuum influenced or not, but if it is, I would be looking foe rotted and broken vacuum lines.
 
The blend doors are cable operated as far as I can tell. Thanks for the response. I'm a little frustrated.
 
The blend doors are cable operated as far as I can tell. Thanks for the response. I'm a little frustrated.
Here is another clue. If I have the setting where it blows out the vents facing you, the same you use when you use the A/C. It seems to blow hotter.
 
That doesn't sound like a water pump issue. Do you have cabin temp sensors? Do you have A/C, could that be running at the same time? I owned an 86 Toy from new, never had this issue but poking around on the forerunner forums they mentioned a couple sensors under the drivers side dash. Good luck.
 
Just general info... Where there is fancy controller where actual cabin temperature is selected, includes a cabin temperature sensor, and ambient/outside temperature sensor, those are always suspect. Your condition would be the in cabin temp sensor.
The Toyota forums have helped me ( 96 Camry ). My problem was the door for fresh air or recirculated air.
 
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Just general info... Where there is fancy controller where actual cabin temperature is selected, includes a cabin temperature sensor, and ambient/outside temperature sensor, those are always suspect. Your condition would be the in cabin temp sensor.
The Toyota forums have helped me ( 96 Camry ). My problem was the door for fresh air or recirculated air.
It has A/C. I was thinking some sort of sensor also. The fresh air actuator makes sense. If I switch it to blow out of the center of the dash I move the fresh air selector. It blows hot out of the center.
 
I had a lebaron turbo that a couple vacuum lines were connected wrong, the egr vacuum and heater control vacuum were backwards.

So at idle with engine hot,heater hoses same temperature or one noticeably hotter?
Some heater hoses are reversible,perhaps core is airlocked.
There are 12 volt pumps that fit heater hoses. But if pump is bad it would only be a temporary fix.

Used to be i could open rad cap with engine running and stat open, could see coolant flow.
 
Other posts as i was writing, center vent stays hot, so its likely a dash control issue.

Have a chevy with a bad actuator, it stays full hot. Man it gets hot now that i flushed heater core and replaced coolant. New actuator waiting to go in.
 
I cannot remember that far back if the HVAC system is vacuum influenced or not, but if it is, I would be looking foe rotted and broken vacuum lines.

Couldn't pay me enough to drive a toyota, but that's a tale of woe for another day.:soapbox:
I don't think this is a vacuum problem. Every vehicle I've had would default to defrost if vacuum is lost (or greatly diminished)...I believe this is a gov't requirement. Besides, vacuum would likely be higher at idle than at cruising speed. All the HVAC in my '98 Grand Cherokee is vacuum operated, I'd imagine other makes were back then as well.
Do you maybe have a partially collapsed heater hose or something that would restrict heater-core flow? Some vehicles have a valve in one of the lines that shuts off flow to the core when the AC is on...maybe it's failing?
 
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I had a lebaron turbo that a couple vacuum lines were connected wrong, the egr vacuum and heater control vacuum were backwards.

So at idle with engine hot,heater hoses same temperature or one noticeably hotter?
Some heater hoses are reversible,perhaps core is airlocked.
There are 12 volt pumps that fit heater hoses. But if pump is bad it would only be a temporary fix.

Used to be i could open rad cap with engine running and stat open, could see coolant flow.
Replaced the heater control valve.
With the radio off, etc., can you ever hear a gurgling noise in the dash? It sounds like an air pocket issue. Several manufacturers had issues like this, sometimes loosening and repositioning the heater hoses can solve it. Try removing the upper heater hose from the core, leave the rest of the system sealed, raise the heater hose above the rest of the cooling system, and fill through the heater hose until you are sure air is purged, reconnect and retest.
 
With the radio off, etc., can you ever hear a gurgling noise in the dash? It sounds like an air pocket issue. Several manufacturers had issues like this, sometimes loosening and repositioning the heater hoses can solve it. Try removing the upper heater hose from the core, leave the rest of the system sealed, raise the heater hose above the rest of the cooling system, and fill through the heater hose until you are sure air is purged, reconnect and retest.
I have tried burping it. My driveway is a hill. Parked in the middle, took the cap off the radiator. Let it run for like 20 25 minutes.
 
best solution .....jus sayin

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we had a dual system in our suburban and the rear core operated the right side of the cabin..? Right side was way off temperature wise. we also had a no heat issue and the coolant was very low. Oh yeah, 92 toyotas came with an electric servo that regulated the heater on climate controlled vehicles, its on the firewall passenger side. It regulated the vacuum to the heater control valve dashpot. I had no heat driving back from Barstow and it was about 40, we froze. Turns out I could have switched vacuum hoses and bypassed it in about 10 seconds with no tools...duh!
 
Heater control valve under the hood that regulates flow to the heater core? If it is clogged or sticking, it can be reducing coolant flow to the heater core even though it looks like it is working properly
 
I have tried burping it. My driveway is a hill. Parked in the middle, took the cap off the radiator. Let it run for like 20 25 minutes.
That does not always work. Many manufacturers are putting bleed screws on the heater hoses because of this. Try what I suggested, or find someone with an AirLift tool before throwing more money at it.
 
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