Ok here goes. I have a 96 Blazer. Thecooling systemwas just flushed at a reputable local shop. I put in a new t-stat and rad cap. It will heat up to about 195 and then the t-stat opens and it cools down a bit. Now my actual problem, The heat will blow warmenoughto keep it comfortable but it never really gets warm at all. Is there a speacial way to bleed the air out of the cooling system? Also, I have read about a heater control valve, where is it and how hard to change it? Any info would be greatly appreciated. Thank you all.

 

There is no heater control valve in the traditional sense. There is an air door internal to the HVAC housing that controls air flow over the heater core itself.

When they flushed the cooling system, did they do the core separately? If not, that is where I would start.

Why did you have the cooling system flushed in the first place?

 

I have owned the blazer for about two months now. The flush was done the day before I bought it, at a Jiffy Lube. They told the guy the antifreeze was weak so it should be flushed so he had them do it. I changed the t-stat and all of that myself. Now I forgot to mention that even with the new rad cap, when it's up to temp I can still take the cap off and not get the normal hot spray of antifreeze that one would expect with a operating temp vehicle. Could that be an indicator of air in the system, and if so is there a certain way to bleed the air on these blazers? I don't know what else to try if the heater core flush doesn't work.

 

This is an indication that the system is not holding pressure properly. The stock cap should be 16psi. Air in the system would still allow for pressure holding. I would bet you have a leak somewhere.

 

I thought I might have had a leak also but levels in the rad and the overflow tank have not dropped a bit.

 

i have the same vehicle and the same problem..i think ill have to pull off the heater core hoses in springtime-and run agarden hose to power flush the heater core [which may be plugged from that DEX COOL KRUD] a new rad cap and new thermostat will follow...my last 2 vehicles never had heat so i am somewhat satisfied with what heat i have for now at least...ive always had problems with water -pool problems,taps leaking ,roof leaks,dishwashers leaking,hot water tank failures,im just glad i dont live near a DAM....[8D]

 

The new cap I bought for it two days ago is a 16 lb cap. Only problem with trying to flush the heater core right now is that with the wind chill where I am at it is about -40 below zero. Garden hoses don't like working when its that cold which kind of sucks.

 

Yeah, weather rarely cooperates with you. I am used to working outside in the cold so it does not bother me so much. My garden hose is inside and fed by mixing valves so I can go full hot for good winter washing!

Anyway, if you do not have any pressure in the system when warm, that is a clear indication of a leak.

The transfer of coolant from the overflow tank requires a sealed cooling system on the radiator side. As the coolant inside the radiator cools, the pressure drops and will drop back past zero, actually creating a vacuum in the system which pulls in coolant from the overflow bottle to make up the difference. If you have a leak, the overflow level may never drop.

 

Why don't you just switch the lines at the heater core and let the water run backwards and flus itself?

 

That could work, or it could plug up the rest of the system...