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Discussion Starter · #1 ·
Ok so I go out and turn on the the truck (02 TRD Taco) to get it warmed up for the wife come out and it is cold inside but the truck is running in the normal range on the temp gauge, take off and start driving, the heat kicks in and is running fine. Stop at a stop light, blows cold air, take off then hot air, stop cold, go hot? Besides the obvious answer of just dont ever stop driving and it wont get cold, Anyone have an answer? Vacuum? Where to start?
 

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Discussion Starter · #3 ·
hmm ok I will check the level, never had a problem with that, and no visible leaks below, but i will check it, anyone else have any thoughts?
 

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like said before, check coolant level. look in oil for milky color if no visible leaks. sounds to me like you have an air pocket somewhere in your coolant system, most likely your heater core cause thats the highest point in your system. if no coolant in oil or visible, take your coolant cap off and try to burp the bubble out by running the truck for a lil while with cap off. start with the truck cold of course. hope this helps
 

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Discussion Starter · #6 ·
Ok thanks guys, it is the wifes truck, so when I get to it I will check the coolant level. Not sure what the fan would have anything to do with it, and I know it isnt the thermo, because it has been right around freezing and the truck holds itself at is normal operating temperature perfectly. Not hot nor cold at idle or highway speeds.

Can someone explain why low level of fluid would change the heat during idle and driving, thanks, I just like to understand things from a mechanical point of view.
 

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Check your Water Control Valve?
Check your Air Mix Servomotor?
Check your Heater Main Relay?
Check your Heater Control Assembly?
All this can be found in the FSM
:2cents:
 

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2 other possibilites: the water pump could be going (at higher engine speeds, higher pump speed means more flow through core, low flow at slow speeds), or heater core partially clogged (again, more flow at higher engine speeds). You would probably not notice higher engine temps due to outside temp.
 
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Can someone explain why low level of fluid would change the heat during idle and driving, thanks, I just like to understand things from a mechanical point of view.
its kinda like water sloshing around in a jar. when you accelerate, its pushing the fluid back to the backside of the car, where the heater core is, and it heating up when is getting the fluid to the heater core.
 

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its kinda like water sloshing around in a jar. when you accelerate, its pushing the fluid back to the backside of the car, where the heater core is, and it heating up when is getting the fluid to the heater core.
2 probs with that:
1. he would only have heat durring acceleration, not normal driving
2. the waterpump overcomes any "G" forces, so a low level wouldn't affect flow to core, unless he was way low (then he'd have other issues)
 

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2001 TACO no heat when the blower is on.

i have a 2001 Toyota Tacoma that will not blow hot air. when i turn the blower off i can feel heat building in the system but once i turn the blower on the heat cools completely down with in seconds. Also i have replaced the Radiator, water pump kit, heater core. Ive checked to see if the valve is opening for the coolant to get into the heater core. its working fine. need HELP. Its getting cold in the North East.
 

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2001 DDSB Tacoma, 2002 4Runner with bumpers and lift, 2008 Rav4
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In my 2001 Taco the heater gave heat intermittently so I tried removing the cable at the water control valve on the firewall. Suddenly all was good. I ended up getting a salvage-yard heater control unit for in the dash (the control with the knobs) and a water control valve. once I installed the heater control unit all was well.
 
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