'07 Taco Won't Blow Hot Air Unless Driving

I've got an '07 Tacoma (PreRunner 4.0L). I've recently noticed that unless I'm driving, my truck won't blow hot air, even if I let it come up to temperature. Once I start driving and get the RPM's up, the hot air is fine. Also, if I'm parked, if the truck has warmed up and I rev the engine, it'll start blowing hot air, briefly. The temp gauge holds steady at the center of gauge once it comes up to temp. Any ideas on what the problem is and how I might fix it? Thanks in advance for your help!

 

With the engine cold take off the radiator cap and check the level of the antifreeze.

 

Most likely low coolant level.

 

My Tacoma recently started doing the same as well.

It also takes longer than normal to blow warm air when driving. Driving on the highway it blows heat at the normal, hot, temperature. Idle for a few minutes in parking lot and it blows lukewarm.

Coolant level is well above the minimum level in the overflow tank. This might be a dumb question, but that means I'm at the correct level right? Or do I have to check what is in the radiator itself?

I've heard that this could be caused by an air bubble in the heater core - could I have one of those and still show the proper level in the over flow?

No leaks anywhere. No odd noises from the water pump that I can notice.

Temperature "gauge" goes right up to the middle and stays there. I plugged in my scan gauge and i'm showing the coolant temp at a consistent 184 degrees. I've heard that if the gauge works that it probably isn't a thermostat.

Changing the temperature setting will blow cold air or a mix so I have eliminated a malfunction in the blend door as a possible problem.

Heater core going bad? (maybe…) Is my water pump not circulating coolant correctly? (seems unlikely)

It's an 09 Tacoma 4.0L. Bone stock. Just hit 110k. Coolant was flushed and replaced at 100k about 6 months ago.

thanks in advance.

 

I think you have an air pocket trapped in the system.

Warm up the engine and then when it is fully up to temperature massage ( squeeze ) the radiator hoses to work out the air. Trust me this does happen all the time esp after a coolant drain flush etc.

 

You can also do some tight figure 8's in a parking lot. Hold the throttle at about 3K RPM's for 2 minutes. The last one is what Ford and GM specify to remove air pockets.

 

heater core was blocked. was able to make it a little better by flushing it, but ultimately the whole dash had to come out so a new heater core could go in.

 

What was it blocked with? There shouldn't be anything in the cooling system that would ever block the heater core. Ever.

Did you do it or did someone else find it? Someone else, I Think you got taken for a ride. I have enever seen a heater core get plugged unless the system was contaminated or some idiot put an excessive amount of "Stop Leak " in the cooling system. Stop Leak is also a contaminate IMO.

If the heater core was blocked the radiator should be blocked also.

 

Heater cores get plugged all the time. Calcium and crap builds up in them and they need to be flushed. Pretty common here because everyone uses their heat and notices when it's not blowing hot enough.