I have a 89 ,4.0 auto. I have a new rad.water pump, thermostat 195.but when it starts hittin freezing out side all I get is warm air.I don,t have a temp gauge just a idiot light.I know the engine is nice and warm and the water is hot.I do have a mechanical fan on the engine and wondering if this is my problem as it,s always sucking cold air,or is there some other reason for this like heater trap door not opening or what.

 

Odds are your heater core i s plugged. A proper back flush of the entire system would probably help greatly.

 

If you get warm air i think your blender doors are okay. it sounds like your heater core is clogged like toaster knight said. this can be an easy fix or a hell hole. depends on how bad it is. but what i would first start by doing is running some prestone cleaner through your coolant and flushing the system. there a million people who have had this problem and a million fixes. some work some dont. but start with that. just dont add radiator stop leak or anything like that, that makes it worse. but clean out your coolant. and if that doesnt work, google or youtube how to unclog it. hope this helps.

 

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Yep. Flush that beast. Once you've done that, toss in a quarter cup of Amway's SA8 laundry detergent. You can find a dealer online. That stuff will clean your cooling system thoroughly, and will not harm anything. You can leave it in there for months on end, so if you get busy and forget about it, no harm done.

I have heard folks say that Dawn dishwashing liquid will do the same thing. Dunno, haven't tried it, but it's probably cheaper and easier to get. Can't hurt to try.