No heat at Idle.

I dont know if this is a common problem but here it goes. Above 1000 rpm I get great heat out of the heater. However at an idle its a different situation. Antifreeze levels are gook and the heater supply and return lines are not kinked. Heater control valve works fine. As soon as i raise the rpm I develop heat again. Needless to say I'm stumped. Any help would be great.

2005 TRD Off Road

 

Reported for racial slur.
















Also, bump.

 

What?

 

Is this only at startup? I always have this problem. Works fine after I run it for at least 30 min. It always will feel either colder or warmer when you're moving.

x2 ?

 

Get used to that guy haha. About half of his posts are kinda useless but amusing. As are about 90% of the people around here. I'd start with checking out the thermostat. Had the exact same problem last winter with mine. And that did the trick
Edit: Don't know if you meant thermostat by heater control valve. If you did then best of luck fixing the problem, heat can be a real PITA sometimes.

 

Yours is an 03 2.7, his is an 05 4.0, how are they similar?

 

They both have thermostats don't they.....

 

And you think my posts are silly and useless?!

 

I'll check the thermostat haven't done that yet. It does it even after driving for an hour doesn't seem to be a start up issue.

 

What he said, I guess it wasn't useless after all. You did bump it Sorry.

 

One has substantially more heat coming from it. We are talking about 2 more cylinders pumping away.

 

You also live in Grand Junction Colorado... Its 47 F. with 97% humidity right now. Your engine is trying...

 

Yeah good point, never know though. Worth a shot, don't know how difficult the 4.0 is to work on. But I'd assume a thermostat is probably one of the easier things. Unless they buried it somewhere that's a pain to get to. I know diddly squat about the 2nd gens. Gonna have to browse around and learn a little.

 

sounds more like air in the system. park it heading uphill or on ramps. open rad cap, start engine run till it burps out the radiator.

 

Belt is new and the temp has never been above the normal range. Water pump is original so I suppose after 178k miles it could be straining at idle. Thanks for all the input everyone.

 

a. weak water pump
b. partially clogged heater core
c. air in system - mentioned above

 

Have you ever replaced your cabin filter? It could help...
I have the 2.7 and on cold mornings here in california (below 40 *F, rare but it does happen) it takes awhile before I starting feeling heat through the vents. It might just be normal...

 

Update and not what I wanted to hear. Bad head gasket, upon startup of the truck the cooling system immediately builds pressure. The mechanic that diagnosed the issue has seen it before. The head gasket is compromised just enough that combustion gasses are making it past the head gasket into the cooling system creating an air pocket. When the truck is at an idle the water pump is unable to overcome the air pocket being generated. As soon as the RPM are raised the water pump is able to push coolant and overcome the air pocket. My mechanic did state this leak is very minor but it doesn't take much to create the problem. The truck does not burn antifreeze or have the usual markers of a head gasket issue. (Swinging temps, low compression) He did perform a compression check and everything looked fine. It wasn't until a bleed down compression test was performed the issue was found. Cylinder 5 seems to be the issue.