Hi, i need some help/ideas.

My heater blows cold air at idle. when driving, it blows plenty of heat, only to blow cold at the next stop light. idle is at 1000rpm

first some background info. I bought the truck a couple months ago, been busy fixing it up and insured it a couple weeks ago. It has been sitting for 4 years due to some frame rust, thats all fixed now. When i got it home(towed) i filled it with water as the rad was empty, found and fixed a couple leaks. it now has 50/50 coolant in it. its a 22re 5 spd

what i have done to it:
rad/cooling system flush
replaced water pump ( leaked)
replaced all 3 "rad" hoses.
replaced t stat
new rad cap
removed heater hoses from heater core and back flushed, it was clear and not restricted
water valve is opening fully, visualy checked operation with hoses off.
rad is full, right to the top. checked this numerous times.
air was properly bleed from cooling system.

what am i missing that would cause no heat when engine is idling?

 

also i was told it could be from the cooling system pressureizing from a head gasket leak or cracked head.
rad cap on or off, the problem is still there. (with or without cooling system pressurized)

the truck runs awesome, with no mixing of oil and coolant. there is a fair amount of steam out the exhuast in the morning, but clears up after 5min of driving. Im not to concerned with the steam as my 97 4 runner does the same thing.

 

Sounds like an air locked heater core.i could hear the air in mine after flushing mine but mine worked its way out. I have had to remove a hose from the heater core on other vehicles and raise it up higher than the heater core and fill it with antifreeze with a funnel and reinstall and drive it on the highway to bleed air out.a good way to check is feel the heater hose on the inlet and outlet of the heater core and see if their both getting hot

 

hi, thanks for the reply.

both heater hoses get hot. i dont have a temp gun but they feel the same.... hot to the touch lol

 

If both heater hoses get hot/warm evenly, then there is coolant flowing through the core. Possibly a bad thermostat mixed with an over-efficient radiator and fan? Meaning its cooling down a great deal when engine isn't running at higher RPMs. Does the temp gauge fluctuate?

 

the temp gauge does fluctuate, well, it has 2 positions, halfway or nothing. it did this with the original t stat as well. At cold start up it will jump right to the halfway point, then nothing, then back to halfway and then stay there. all that within the first 2mins of running. i suspect the gauge is faulty

the fan clutch functions properly
the rad isnt plugged, even tried a good spare i had

to me it seems like a "flow" problem.

 

So do you hear the blend door open and close moving the knob from got to cold?i easily removed the duct from the blower housing to the heater box in about 10 min and sprayed out my heater core with foaming ac coil cleaner you can get at homedepot or lowes .then sprayed liquid Lysol out out a spray bottle to clean the smoke smell out of mine and it made a big difference on heat out put.but even if the heater core was stopped up with dust you should still be getting some heat out .

 

Did u burp the system?

 

yes i have, numerous times

yes i hear the door moving. there is plenty of air flow, its just cold air at idle

 

The only other thing that I can think of is what temp t-stat are you running and if it isn't a oem with the little bypass in it did you drill a small hole in it so it has constant flow?next would be is the fan clutch working too much? I had to Bend the spring on mine a hair so it didn't run when it was cold .when I start mine it runs until I give it a few revs then the fan noise stops .last thing would be it wouldn't surprise me if there was a bit of buildup were the rubber hoses go into the steel lines

 

Between the fan clutch adjustment and the t-stat switch to 190 degrees and the little hole drilled in it I have heat were before I was lucky to get Luke warm after idling 20 min.oh and drilling the hole in it keeps it bleed out too

 

thanks for the reply.
i changed the t stat, i asked for a 190deg. so hopefully thats what it is.
the new t stat had the little air bleed. after i drove it for a few days and some research later i took it out and drilled the hole in it. it had no effect on heat.

 

I would almost pull the t-stat and check.The autozone here kept tryin to sell me on a 180 they said that was oem temp so I went to orilleys and they had a 190 in stock.The funny thing is the 1st one I bought from autozone in the summer was suppost to be a 190 but sure enough after i pulled it last month it was only a 180.I try to look on their screen when I can to make sure they give me the right part alot of dumbasses work at parts stores around here.Just last week I went to get a compression tester and the guy behind the counter corrected my 2x it was a piston ring compression tester and couldnt find it in his computer untill his manager told him to look up a compression tester.lmfao .Oh and before i fixed the fan clutch and swapped t-stats I had a piece of cardboard over a 1/4 of the rad and that helped alot.

 

Another thing it could be as you though is a flow problem.I replaced my headgasket yeaterday and noticed the old headgasket had build up in the coolant ports that were 50% smaller than they should have been.The smaller ports were prob 75% smaller than they should have been.I have only drove it once since then and it seemed to heat up quicker but im not for sure ill let you know how it goes after a few days of driving it.

 

well i havent driven it much, but the few short trips i did make everything was working normally. hopefully it was just an air pocket

thanks for the help

 

hopefully it works out for you

 

thanks, i hope so to. havent been driving it much , but that will change next week