Ok, of all the things to stop working my heater seems to be on it's way out. It's been raining all day and the temps are pretty cool, in the 40's. When I left work I turned on the defroster and moved the temp slider all the way over to hot. After a couple of miles I noticed that the air blowing off the windshield was still pretty damn cold. Now I know that the windshield is pretty cool, but I've driven the car in much colder temps, something wasn't right.

I hit the button and switched fromd defroster to vent. I was greeted by cold air coming out of the vents. I slid the temp slider all the way to the cold side and I got cold air, just like one would expect for the outside temps. I slid it back to the hot side and I got only slightly warmer cold air. I fiddled with it all the way home and couldn't ever get any heat out of it.

I did notice that if I put the slider all the way towards cold for a few seconds and then move it back to hot I'll get a brief moment of warmer air, then it cools back off. It's almost as if the fan is cooling off the heater core so much that it can't keep up, when I divert the air from it for a little bit it heats back up again.

The car's running just fine, both temp gauges are right where they should be, full operating temp. Is it possible that the heater core is clogged up, not allowing warm coolant to pass through it? I've had the car for 3 winters and for 2 of them the heater never seemed less than adequate. In fact I was running a 160 thermostat for one of them. This winter I swapped back to a 180 because I didn't feel like it was getting very warm with my 160. I just chalked it up to possible cooler temps and part of it being in my head. Now I'm thinking that my heater has just been getting less and less efficient. Even with the 180 I don't feel like it was blowing as warm as it should. Now it's putting out next to nothing.

Any thoughts, ideas, experience with this sort of problem? Is there a good way to flush just the heater core? For those who might not know the car's a 1992.

 

I'm not sure about the LT1 cars, but on my L98 it is relatively easy to flush the core. On the engine side of the firewall, there should be two hoses going to the heater core. I would start by squeezing these hoses when cool, if on or both are crunchy the core will probably be clogged. Then, run the car for awhile and feel both hoses, they should both be warm. If one is significantly cooler than the other, you have a clogged core. With as much work as it is to change one of these, I would definately try flushing before replacement if the core is not leaking. Be wary of highly acidic flushes that could eat the solder holding the core together.