These were some good instructions, thanks for posting them. I flushed mine today and got alot of 'gunk' out of the core.
The only issue for me is, after flushing the core, I still had the same problem of lukewarm heat. My temp stays steady at 160 degrees at idle. Driving its about 170 and a tiny bit more heat comes out.

I'm thinking its the thermostat. Could I be correct? How could i check that?

Thanks,

J

 

Sorry for the delay, I am out of town. Yes, the thermostat sounds like it could be stuck open. I would replace it and see if that takes care of your problem.

 

It is the t-stat for sure I had one fail on me and I had a freeway drive home at night. It wouldn't go above about 150 beause of the high airflow through the radiator.

 

I need to do this pronto. It takes a really long time for my truck to heat up. And even when the temp guage gets up there it still blows hot air. Now, if I'm on the highway, or it has been running for more then an hour at a decent speed I will sometimes get luke warm air, but it never is hot.... time to find a friend with a heated garage.

 

Hi, I just joined this forum. Thanks for the great info! I just back in the house from flushing my cooling system. I used the prestone kit and ran it until it was clear. I refilled everything, yet my heater is still barely lukewarm. The inlet hose to the core is HOT, the hose going to the water pump is still cool(?) What is going on??? Do I need to do it the opposite way, flush from the water pump hose, back. Thanks a million!!

 

yes, I would do a reverse flush on the heater core. that way all the debris comes out of the core, not plugged further in it. I jut did my 88 dak yesterday for te hell of it and I couldnt believe how much crap came out. I had good heat before but now its amazing

 

Ok, weird things are going on. Yesterday I did the Prestone complete system flush. Today I backflushed the heater core...twice. I took it for a spin and it really acted up. I started to get warm and I am thinkind what I did worked. Then it got ICE cold and began to overheat (it is15 degrees outside). I barely made it back in the driveway, then as I pulled in the driveway, the temp started to go way down and the heater started to blow lukewarm air again(????) HELP!!!! Is this a thermostat issue? I changed that once but bought it from Napa, the same place I bought some sh***y spark plugs. Does anyone have any ideas???

 

sounds like you have an air pocket in the engine. I would take the rad cap off and fill the rad up as full as you can get it. then start the truck up and rev it between 1200-1500rpm and keep filling the rad up as it's going down. and that should do it.

remember that you will have to wait for the truck to warm up before the coolant starts flowing.

 

Great!!! It must have been the air bubble!! I went from none to hot. Thanks for all the help, now I have a super clean cooling system with all the hot air I need. I am not out of the woods yet however. I have a condensor that is leaking. So come late spring, I will be working on that. Does anyone know if there is a thread for that somewhere?

 

It is done pretty much the same way you change out a heater core.