No heat unless the RPMs are up

Hello all.
My ‘05 with 230k has stopped blowing hot air at an idle. It gets warm only if I rev or drive. My mechanic is making too much money off of me theses days having just put $2500 into it I’d like to fix this issue myself if it can be resolved without too much working on my truck in the cold.
So any thoughts from the collective about what’s going on and what I need to do?

TIA

 

I had this problem on an old first gen. I replaced the thermostat to one that opened on a higher water temp and it solved my problem.

 

When was your last water pump ?
When was your last antifreeze flush ?
What condition is the radiator in ?
What condition are the radiator hoses in ?
What condition are the heater hoses in ?
When was your last thermostat install ?
How does the heater core look ?

 

Assuming your coolant level isn't low, it sounds to me like your thermostat may be stuck open. Your engine (and transmission cooler routed through the radiator) can't generate enough heat to over come the systems cooling capacity until under load.

 

05? sounds like head gaskets.

 

Could be a multitude of different things. I had a vehicle I worked on last week that just needed the Heater core backflushed. I opted to put in a warmer thermostat because the engine wasn't running where I would have looked. So after the flush and thermostat my said vehicle was blowing hot air all across the board. If you don't want to pay your mechanic, I would start with the basics. What is the engine temp while driving? Have you checked coolant level? An air pocket in the cooling system could also cause some issue as well.

 

Well good people. Embarrassing as it is to admit Key-Rei nailed it. Only she gave me too much credit. The coolant was low. I had it flushed and it’s all good.
Worth the cost of entry right there.
Thanks Key-Ray.

 

Your anti-freeze was low ?
How did the anti-freeze get low ?
Was there any signs of leaks ?
When the shop flushed your cooling system , did they pressure test after the fluid was topped off ?

 

This is something they really should teach in drivers ed class. When the heater stops blowing hot air, SHUT OFF THE ENGINE!

 

These are important questions. The cooling system in a Tacoma is rock solid. I've added coolant to this truck maybe twice in it's entire life (and I check it regularly). If your coolant is low, there's a reason. And you need to figure out what it is.

The opposite is also true...if the engine temp is warm the very first thing you should do is blast the heater. So it's not exactly intuitive to most.

 

wait so you dont redline it till it starts blowing hot again?

 

Yes they did a pressure test and no leak. It has. 230k miles on it and I can’t think of a time when it would have been opened, or drained. I probably did some service around 150k but that’s a long time ago. I’m kind of a set it and forget it kind of guy. I keep my equipment stock and use OEM so I don’t have to fiddle with things. I buy Toyotas because I am a durability snob and also a space-shot so I need things to just work. So far this truck has done me right. I change the oil every 5000 mile whether it needs it or not and I wash it seasonally and I get the recalls done. But I can tell you there are no stains on my driveway that aren’t because of some GD carburetor and I did just have my mechanic go through it to help me decide weather I should keep it another couple years or consider something newer. He didn’t spot anything other than the suspension work I had done and a muffler/C.C.
So all told I feel it just evaporated after 15 years of use.
if in three weeks I learn something is wrong I will come back and eat crow for your satisfaction.
Again thanks for the input, worth the price of admission.

 

Simplest thing is likely low coolant (check the radiator, not just the overflow). If your coolant is low, you are leaking it somewhere. Adding more will fix the heat issue short term.

 

Your thermostat is stuck open. Cheap part and easy DIY project.

 

Get a clue. You don't know what you're talking about. Check the cabin air filter and engine thermostat.

 

ok.....