Heater and Cold Air Problem

[04MRADR]

First let me say thanks to all those members who helped me with a recent problem where the heat was coming thru my vents and no place else. As suggested by various members and confirmed by my mechanic the blend door was broken. A heating and air conditioning shop he sends his work to removed and replaced the Heater Plenum door assembly, HVAC Blend Door Actuator and the Heater Core on 12/22/17. Everything was working fine for a few days when all of a sudden I had to drive several miles before the car threw heat and then okay. Turned out my radiator was leaking and had to be replaced on 12/29/17 and for extra measure thermostat was replaced since I had the original. Everything was working fine until the past couple days when an old problem I had for years popped up again. The problem was whenever I came to a stop in the cold weather the heater would blow cold air. After I gave it the gas and drove for about 5 seconds the hot air came on again. I lived with the problem for the past few years. My mechanic felt it was probably a heater core problem.

About two days ago this problem started again. But also if I coasted down a hill without pressing the gas the cold air came thru as well. However the heat came on instantaneously when I pressed the gas with no 5 second delay as prior years. By the time I got home (about a 7 mile trip this morning) the heater blew hot air even when at a stop.

Any idea what could be causing this ? It's been in the single digits on the east coast here the last few days with the extreme cold. Didn't have this before this cold snap where temperatures are in single digits overnight and in the teens during the day with wind chills below zero. Is it possible new parts aren't quite broken in yet or is this something else ? Appreciate help on this. Thanks in advance.

[Turbov6Bryan]

I would encounter this every friday and sunday night sitting at the same stop light with my heat on full blast, just to realize it dwindled down to cold air.

You need to add more coolant to the cot, the cross over tube.

You have just enough coolant to keep the car working, but when you stop, there isnt enough coolant to push thru the core.


Please park the car nose up, like a very steep driveway. Fill the cot and squeeze the heater hoses to bleed the air out.

100% the issue you are having is not enough coolant.

[04MRADR]

First let me say thanks to all those members who helped me with a recent problem where the heat was coming thru my vents and no place else. As suggested by various members and confirmed by my mechanic the blend door was broken. A heating and air conditioning shop he sends his work to removed and replaced the Heater Plenum door assembly, HVAC Blend Door Actuator and the Heater Core on 12/22/17. Everything was working fine for a few days when all of a sudden I had to drive several miles before the car threw heat and then okay. Turned out my radiator was leaking and had to be replaced on 12/29/17 and for extra measure thermostat was replaced since I had the original. Everything was working fine until the past couple days when an old problem I had for years popped up again. The problem was whenever I came to a stop in the cold weather the heater would blow cold air. After I gave it the gas and drove for about 5 seconds the hot air came on again. I lived with the problem for the past few years. My mechanic felt it was probably a heater core problem.

About two days ago this problem started again. But also if I coasted down a hill without pressing the gas the cold air came thru as well. However the heat came on instantaneously when I pressed the gas with no 5 second delay as prior years. By the time I got home (about a 7 mile trip this morning) the heater blew hot air even when at a stop.

Any idea what could be causing this ? It's been in the single digits on the east coast here the last few days with the extreme cold. Didn't have this before this cold snap where temperatures are in single digits overnight and in the teens during the day with wind chills below zero. Is it possible new parts aren't quite broken in yet or is this something else ? Appreciate help on this. Thanks in advance.

Thanks Bryan about the lack of coolant but when my mechanic replaced my radiator last week he filled it with coolant. He ran the car for about 15 minutes, revved up the engine for long periods to heat the car up and I presume make sure the coolant level was where it was supposed to be. So I wonder if I lost some coolant over the last few days and I actually have another leak somewhere else ? I had a intake manifold gasket leak in a 1980 Mercury Marquis I owned so I know leaks can occur in places besides radiators and hoses. I'll be looking forward to other responses but will pass along what you advised to my mechanic also.

[Turbov6Bryan]

He didnt do it correctly. There is a procedure on how to do it.

I clamp the big hose on the overflow, then pull the plug on the cot tube and fill while squeezing the hoses.

You are missing about 2-3 quarts. If you had a leak, you would smell it.

Take it back to him and tell him the heater core is fine because you have heat when the coolant sloshes back with gravity.

GO park on a steep driveway and fill it.

[fastblackmerc]

The correct way to burp the cooling system:

http://www.reischeperformance.com/refill.html

[RF Overlord]

^^^what Bryan and Jim said