does anyone have a trick for getting air out of the heater core ,ive had this happen on other 2nd gen trucks before and it usally fixes itself after a while but this one wont bleed itself out so i have a lukewarm heater\defroster and i have the truck in Denver for this winter ,this happened after i replaced the coolant a few years ago .radiators full and truck never gets hot in Nevada summers and i checked heater doors and valve control .any advice appreciated . note : ive only had this happen on original A\C trucks perhaps the heater core is positioned differantly

 

One possibility is that the heater core has enough sediment or trash in it so that it doesn't exchange heat efficiently. You might want to consider doing a flush on the heater core alone to make sure this isn't the case. Here's a video about that:
My '78's cooling system will burp itself out with the radiator cap off, truck on level ground, start & run until thermostat opens, heater turned on, fan speed at low. It takes about 5-10 minutes of occasionally topping off the coolant until bubbles stop appearing and there is no drop in coolant level. If the cooling system will not burp itself out that way, one trick is to jack up the front of the truck & put it on jack stands or ramps. This puts the radiator at a higher level than the heater core, and the air in the system will more easily rise up & out the open radiator cap port. The engine has to be run like the "level ground" method, so make sure the truck has the parking brake on and/or the back wheels are securely chocked (I do both for safety). Also make sure you have sufficient coolant in your overflow tank and for god's sake be careful! Hot coolant is positively no fun to get splashed on you.

 

I've found that when "burping" the system like that, nose high on ramps, a hill, etc, you can put the radiator cap on to the first portion of it being tight. IOW: Place the cap on, give a slight, or 1/4, turn to it. That will keep it "on" the neck, preventing sprays/splashes, but not restrict the water from flowing back and forth to/from the recovery tank. Lets air bubble out, go to the recovery tank, and thus overboard, but not allow air to go back in. Just keep enough water/coolant in the recovery tank.

I let mine run like that for about 20-30 minutes, heater full hot, fan low. Shut down, and let it cool down until I can touch the radiator where the upper hose goes into it. Pull the radiator cap off and top the coolant, if required. Same for the recovery tank. Then I just put the cap on properly, ie: all the way tight, and drive it normally. Keep an eye on the recovery tank for a few trips, in case more air bubbles out of a corner someplace. And it will.

All else fails, IE: there's still air stuck in it someplace you just can't get to come out, which happens in my pickup all the time, but not the 4Runner for some reason, you can get a bottle of stuff called "water wetter" at most auto part stores. It essentially lowers the surface tension of the water, which is what holds bubbles in the little corners they like to hide in. The bottles don't hold a whole lot, so it's pretty easy to add into the system without taking much out. I just pull the radiator cap off, put my hand over the neck, and give the upper hose a few squeezes. Pushes the water out into the recovery tank, so I can add the water wetter. Just put the cap back on, and away I go. It take a bit to completely circulate the water wetter, but it will get the air out. Again, keep an eye on the recovery tank water level.
As I understand, it's safe for cooling systems, won't cause corrosion anyplace, or damage sensors/thermostats.

Good luck!
Pat☺

 

My burping setup. Everything is re-used. Not bought. Metal container may be better becoz it would not get soft.

 

My burping setup. Everything is re-used. Not bought. Metal container may be better becoz it would not get soft.

Chris Fix's flush method is thorough.

 

wanted to say thanks for advice , i parked truck with front end on hill ran it with radiator cap off till it started getting hot ,put on cap and vigorusly squeezed top radiator hose for a few minutes ,works now great.i forgot to mention when i started thread that i run a default open thermostat that may have added to the problem somehow

 

Umm...YEAH!
Always best to have a properly functioning tstat in. The truck will warm up faster, and on those cold days, it keeps the engine at the correct operating temp. Allows the ECU to set the mixture and timing correctly for optimum operation of the engine.

The system is also designed to have the restriction of the thermostat in it. It keeps the water from flowing through the radiator too fast. Yes, that's a bad thing. It runs through TOO fast, and it won't have time it needs to exchange the heat to the air flowing through the radiator. Thus, the engine will run hotter than without the restriction provided by the thermostat. Also, the thermostat will only open enough to allow the engine to operate at the correct temp. It will open and close as needed to keep the temp as close to it's design temp as possible. Very beneficial to the ECU, as described above.

I didn't believe all this when my mechanic friends I worked with told me that. They told me to try it. So I took a spare tstat I had, and ripped all the pieces off it. First, I ran my truck without a thermostat at all, and yeah, the truck wound up running too hot. So, I put in the modified thermostat I had created (destroyed??), essentially just the plate with the hole in it, and again, it ran too hot. Not as bad as wide open, but getting close. Then, I put in a new, tested, thermostat, and bingo, the temp gauge, for what good that is, locked in, and stayed at about 1/2, in my pickup. I was convinced.

All this was in the summer, in lovely (sarcasm!!) Yuma, AZ. Place where 110°F is a normal afternoon. Sometimes hotter, sometimes it even cools off to 100°F! My trucks always had correctly operating thermostats in them, and it was never the cause of an overheat. All summer long, you could see cars pulled off the side of the road, overheated. Mine, never.

Just my thoughts on thermostats. I get so few thoughts any more...
Pat☺

 

2ToyGuy i think your misunderstanding me .a default open thermostat is always open until engine warms up and then closes partialy to keep temp at 180 or whatever its rated for and if it fails it goes back to full open position saving a headgasket if your not watching the tempature gauge ,toyota put them in some years trucks .i highly recommend them to everyone ,theyve saved me a lot of grief over the years . I agree with you on keeping the cooling system up to snuff i live in nevada and i see a lot of broke down cars on the side of I 80 as soon as it gets hot every summer .as soon as it hits triple digits there is lots of blown tires and overheated cars