Cooling system problem, no circulation/heat..??

Hi all, my taco was in a front end accident and I replaced the radiator and expansion tank, filled up the radiator and about half the expansion tank, hooked up the hoses and fired it up.

Sounds good and healthy, but after she got up to temp I turned on the heater to check that I had heat and circulation through the heater core, but got cool air. The temp gauge continued to rise. The upper hose is hot and stiff, the lower hose is cool and easily squeezable, no coolant seems to have left the radiator, no bubbles or anything when I remove the cap, I’ve tried getting it up to temp and removing the cap several times, there is always a ton of pressure let off, but never any bubbles once I can look in.

It seems the coolant is totally stuck in the radiator and not circulating through the system. Unfortunately I can’t drive it to assist in burping because I’m also installing a lift and refreshing suspension components, can’t put on the wheels and lower it to roll at the moment (read in another thread that driving it was a good way of burping the system).

I do have a spare thermostat.. should I replace that or does this sound like another issue? Am I burping the system correctly by letting it get to temp and then removing the cap?

I have a feeling it is the T-stat, but I’m really hoping I’m just being dumb and over looking something simpler. Thanks all

 

Replaced t-stat.. warming her up now..

 

I think you're on the right track, but let the truck get to temp with the radiator cap off. You should see bubbles and then a rapid decrease in coolant once you get to operating temp. Be ready with coolant to pour in the radiator so you dont suck more air in.

 

Still no heat, but I did just now try taking the cap off and letting it run, while massaging the upper hose I thought I may have heard something, thought maybe the level went down a hair.. so I started adding some coolant and got some EXPLOSIVE burps lol, like duck and cover level burps..

Thing is.. it’s still not circulating, no heat, and the radiator is still sitting full.. am I just not being patient? Do I just need to continue this process until things fall into working order? I only have about 2/3 more of a gallon of coolant (out of 2ish, loss some to the t stat change). Gonna get back out there and try more burping

 

It can take a while......and it doesn't generally all happen at once.

Sometimes its damn near impossible to get air out without a spill free funnel. Local parts stores carry them and they work great. If you have more trouble pick up the Lisle Spill Free Funnel kit when you go out for more antifreeze

 

Always turn heat to on before starting engine after radiator drain and fill.
Waiting till engine reaches temp then turning on heat can create air lock.
Let engine cool, turn heat on, start engine, wait at least 10 .min.

 

Roger that, I’ve had the heat on the entire time, ill worded previously.

Just went to pick up more coolant, gonna give it another go now.

 

Should I have the expansion tank empty, half filled, etc?

 

It won't draw from there with the radiator cap off....wait and be on the ready with coolant for when your radiator level drops.

 

Once your bubbles stop and you have heat top off the radiator, cap it, then worry about the overflow tank

 

you can fill the block from the upper hose that should get coolant on both sides to the thermostat.

 

Ok.. here’s where I’m at:

I filled the block from the upper hose, had the heat on, cap off, and turned it on. I’ve been idling for about 40 minutes and the temp is rock solid just below the half way mark on the temp gauge, so that’s good. Haven’t gotten any discernible burps..

I still don’t have heat. After 40+ minutes of being up to temp and stable.

I’ve tried to common sense troubleshoot.. I felt the hoses going into the heater core valve (pardon me if that’s the wrong term) from the engine and to the heater core, both are hot. The hose returning to the engine is cool.

I disconnected the hoses at the heater core valve and confirmed flow, coolant is pushed out both from the engine and from the valve.

I get no flow from the heater core to the engine.

So two questions come to mind..

A.) How do I restore flow within the heater core? Earlier I had poured coolant in one hose and it flowed out the other.. so I’m at a loss as to why it’s not flowing right now.

B.) Is the engines coolant flow affected by the heater core not flowing? I would think not given I’ve idled at stable and good temps on a warm day for so long.. but I don’t want to assume it’s safe to drive even without heater core flow if it’s going to lead to me overheating.

 

Here’s an image of what I mean.



As mentioned above, I had earlier poured coolant from the intake side and gotten coolant out of the return side of the core. The flow from the engine and valve isn’t the most powerful in the world, but its definitely moving, so I’m not sure why I’m not getting anything.

I also check in the cab to make sure I wasn’t leaking under dash, no leaks.

 

I just inspected everything to make sure I don’t have any small leaks introducing more air into the system. No leaks or weeping anywhere I can see, dry as a popcorn fart.

 

in your picture the "In" flow comes from the thermostat bypass tubing that on the 3.4 sits under the lower intake manifold which comes from the back of the thermostat housing in the block, on the 4 cyls I believe it comes from an external tube on the D/S of the block... it sure does sound like your heater core has air trapped or is plugged. I would take a garden hose and back flush the heater core with both lines disconnected and see if water comes out the "In".

 

The flow through heater core will probably clear itself while driving and no it won't blow a head gasket because of the heater cores lack of flow.
Finish the other repairs and test drive it

 

Gonna try the hose back flush really fast because it’ll only take a minute, if that doesn’t get it then I’ll just let it go and finish buttoning up the rest of the stuff so I can drive it. Will report back shortly.

 

Ok, I’m happy to report all systems are go!

I disconnected both hoses at the heater core and grabbed my hose, shot through for a back flush first, then in the regular flow direction after that for good measure. Then I connected the heater core inlet hose, and left the return hose disconnected so I could watch for flow exiting the heater core. Fired the truck up and watched.. as the truck got up to temp I wasn’t seeing anything coming out, then I saw a slight movement inside the tube the hose connects to.. it looked like it wanted to go but it was just kind of pulsating there, so I grabbed the throttle cable and gave it a tug, and BOOM, flow! Hooked up the hose, topped off the radiator, and went inside to check if I had I heat, which I am extremely happy to report I did.

Thank you @Natermator, @Black DOG Lila, and @Glamisman for helping me figure it out

 

Glad you fixed it
Always good to report the cure here it will help many in the future

 

The Toyota Repair Manual doesn't say you need an elaborate procedure to get air out of the system. The air will come out on its own.

The lower radiator hose is supposed to be cold. If the engine is idling only a very small amount of cold coolant needs to be circulated into the engine to keep it at normal temperature, so it may seem like coolant isn't flowing into the radiator.

The water pump circulates coolant through the heater core even before the thermostat is opened, as long as the heater valve is open. Revving the engine will increase the flow and pressure and will push out any air.