Inconsistent Heat

[bdubbin]

So it's winter... some times I get heat in my 4Runner (2006 V6) and sometimes I don't.

I spent 45 minutes with no heat this morning. I park in a garage that was probably 10C. It was about -10C outside. Engine temperature gauge indicated that the engine was warm after maybe 10 minutes of driving but I couldn't get any heat into the cabin. At a red light I turned the truck on and off to see if that would solve anything. No change.

I turned the 4Runner off and left it for 5 minutes outside. When I fired the truck back up again I had hot air; not just warm but hot.

I've noticed over the past couple months that I've inconsistently being getting cold air from my air vents even after the engine is warm and the heat is turned to max. I change the settings (floor/defrost/auto/fan speed/temperature/everything I can think of) and I can't consistently get hot air.

Any ideas what's going on?

 

[Rocketdog]

Checktthe heater hoses coming to and leaving the firewall. If they are warm/ hot, then you have most likely have a problem with either the blend doors or the blend door motors that operate them.

 

[fourwd1]

have you done any work on the cooling system lately?
You may have an air bubble in there, which can be gotten out by bleeding the system.

 

[bdubbin]

Thanks I'll look into those.

I haven't done any work to the cooling system lately.

However, this morning was -30C and again I didn't have any heat... similar to yesterday traffic was moving at a snail's pace. Today I held the RPM's at 2 - 3k and did get heat to flow. After that the heat was okay. Does this point to something other than what's suggested above?

 

[ARunner]

If your temp gauge is looking normal, that indicates your thermostat is acting fine. The other possibility is you are low on coolant, but what you describe doesn't sound like that either. I agree it sounds like the electric device that allows heat to flow through the heater core and thereby provide you warm air in the cabin is a likely candidate.

Best way to isolate this IMO is turn the heat all the way to hot before you turn off the truck and park for the night. Confirm its hot. In the morning see if the heat indeed works. In this case the mechanism that allows for coolant to flow through the heater core should be out of play since it was opened already before you shut the truck off. Good luck. Sounds miserable. Hopefully you have some heated seats at least.

 

[RPS13]

No heat at idle means your coolant is low. Check the level and bleed the cooling system.

 

[scw1991]

first thing would be to verify the stainless steel heater core lines entering the cab from the engine bay above the gas pedal are hot. If so, then I'd suspect the blend door actuator is the culprit which is also located on the drivers side directly above the lower vent.

No heater core valve on the 4th gen that I'm aware of.

 

[bdubbin]

Thanks everyone... embarrassingly my coolant level was low. I fail. But I have heat now!

 

[RPS13]

What sort of prize do I win?!?!?


BTW - keep an eye on your head gasket and your water pump (from under neath). Losing coolant is a bad sign, and hopefully it's just your WP weeping.