Heater not working

The heater is not working. The air is moving fine. I have good flow out the dash vents, floor vents, and the defrost, but the air is not hot. The inlet hose to the heater core is hot and the outlet one is cold. I flushed the heater core, and a little bit of trash came out, but began flushing clear pretty quickly. Tried the heater again. Heat still doesn't work. Flushed it again for close to ten minutes, alternating between constant flow and bursts of water. Flowed water through both the inlet and outlet side. The heat still doesn't work, and the outlet line is still cold.

The truck is 2007 SR5 with the 4.7.

Any one have any ideas?

 

Air in the system. When was it last flushed or changed? Or the core is effectively blocked.

 

Not sure when or if it has been flushed or changed. The previous owner did not have much info to pass on to me. I have had the vehicle for about 5 months, and I haven't done it yet.

 

Find the coolant inlet line at the firewall. Then the outlet line. Without getting into the whole system I’d recommend flushing the heater core individually. I use my shop vac with a couple of smaller adapters to connect to the heater inlet hose. Have a capture hose running from the outlet side into a bucket. Two reasons, capture the mess but also to check the mess to see what’s coming out. Push the old out, measure it. Pour in a flushing agent with water and let it sit to dissolve any kind buildup. Then use your vac to push that out. This should give you a really good idea as to the contents and condition of the interior of your core. Fill it back up and reconnect. Drain the engine and fill with same flushing agent. Flush your whole system and add new coolant, but make sure you don’t get any air blocks. This should fix your problem.

 

^ and make sure you don’t have air in the coolant, after you flush bleed the coolant and see if that helps first

 

I believe you may have an issue with the blend door. The older Toyota trucks had a valve that would shut off flow to the heater core. But that's gone now. The waterline goes from the engine to the heater core then to the transmission then back to the radiator and always flows. If the hose that goes into the heater core (under the hood) is warm then most likely you are getting flow. I believe there's a blend door that moves to either force air to go through the heater core or around it. There's small electric motors that move it. The door could be stuck or something broken. If there is a blend door I don't know how easy it would be to see if it's working. If it needs to be repaired it could mean removing the dash to get at it. I believe the electric motor can be seen though.

 

If it’s a blend door then both hoses into and out of the heater would be hot, one is cold indicating there is a block

 

Why would one be hot and not the other? Both should be cold if it's plugged/not flowing. If it's plugged I wouldn't think it could be flushed. I guess if it's close, but not fully plugged enough some fluid could get through. Hot on one said and cold on the other sounds like the heater core is doing it's job and removing heat. That's why I was thinking the blender door could be the issue. It would be nice to know how freely the water flowed while it was being flushed. Also if the transmission part was also flushed or just the heater core.

 

The heater core is no different than the radiator. It receives hot fluid and cools it with a fan blowing through it. That doesn't mean it makes it cold. Both will have have hot in and warm out. If it's hot in and cold out there is no flow.
In the radiator that means engine overheating. In the heater core that means no heat.
I had a 2001 Silverado that when coolant got too low air got trapped in the heater core and the only way to get it to blow heat again was to pull the heater core lines and flush with water to get the air out. @Cruiserpilot stated the fix earlier.

 

@82nd Airborne is right