Anyone have any idea why my heater will only blow out hot air when my car is moving? If I stop at a red light or such, then it blows out cold air. It's an almost instantaneous switch from hot to cold.
isn't that dangerous? I would think that while the coolant is hot and under pressure it would be a bad idea to loosen the cap....There's air in the line. It doesn't matter that you flushed it. Whomever did the flushing got air in it.
Fill the radiator at the cap while it's hot and running, and then burp it.
If that doesn't work, start worrying about other causes.
Bitter is right. The radiator cap needs to be the highest point in the system for the air to come out. The way the car sits the heads are higher than the radiator. A steep hill with a curb on the side works great. Just pull the passenger side front tire onto the curb. Also, make sure the heater is on in the car when attempting to burp the coolant.you run the car upto temp with the cap off and the front of the car raised slightly.
To my knowledge you just squeeze the lower hose. Just grab it and squeeze it several times with the engine running. This will basically push the air pockets out of the system (the air will leave through the open thermostat hole).You squeeze the hell out of the upper and lower hose with the radiator cap off when the car is warm to get air bubbles out.
Yes, there is air trapped in your heater core.Anyone have any idea why my heater will only blow out hot air when my car is moving? If I stop at a red light or such, then it blows out cold air. It's an almost instantaneous switch from hot to cold.