Rome

We went all last winter with no heat because I couldn't sort out this problem. This year it has to be fixed.

The heater began blowing hot and then cold intermittently at first, and then there was no heat. I had the coolant system flushed last year and that seemed to bring back at least some degree of heat for a small period of time, and then it was back to cold, cold, cold. My first assumption is that the heater core is blocked with something, and that maybe that first coolant system flush might have loosened up the blockage for a short period. The radiator is full, and the car exhibits no other symptoms.

Has anyone else lost their heater function, and what kind of repairs were required to fix the problem? Thanks!

96t-bird

Check your thermostat and the heater control switch.sound like valve is not opening door for the heat cycle.

Stevo86

If you suspect a plugged heater core you can take off the lines at the firewall and use a hose to flush it through. A regular garden hose isn't going to make enough pressure to hurt anything. Although it kinda sounds like a blend door issue.

petrock

A good way to test if the heater core is blocked is by getting the motor to operating temps and checking the two hoses coming out of the firewall on the passenger side from the heater core. If one is hot and the other is cold/warm, then the heater is blocked/restricted. If both are hot, then the heater core is fine, coolant is flowing through it nicely and the problem is somewhere in your dash. If both are cold, then the problem is somewhere between the firewall and the water pump.

If the core is blocked, back-flushing it is fairly simple and can be messy. There are a ton of video’s on youtube about how to do this. A regular garden hose will do just fine for this purpose. I would also recommend going to your locate auto parts store and picking up a couple feet of hose the same inner diameter as the hose coming out of the firewall. They are different diameters, so you need to buy two lengths of hose. This way you can route the extra hose out of your engine bay, and into a bucket so you don’t get coolant all over the place when you back-flush it. Makes cleanup a lot easier.

If the core isn’t blocked, then it could be a blend door as others suggested. Good luck...

uberstang1

Issue u described can also be a head gasket, does the car overheat?

mbeer

Also sounds like it could be an air pocket somewhere in the cooling system.
I'm fairly new to Mustangs but I know with some other vehicles there is a bleeder screw somewhere near the t-stat housing to let the air out otherwise it prevents the t-stat from coming up to temp.

uberstang1

You burp the 2v directly off the expansion tank