AC has nothing to do with your heater core. so you dont have to mess with it at all when you flush your cooling system

 

The Chilton manual said that theAC systemhad to be depressurized before removing the heater core. That didn't make sense to me but I figured they probably knew what they were doing. So the AC definitely does not have to be depressurized??

 

ya, if your removing your heatercore, then you have to diconnect the AC.

 

Is there a reason you are replacing it? It is leaking? If it sin't leaking, I would just flush it. Save yourself quite a headache.

 

good info here, im gonna do this on my 97 this weekend, it blows heat, but not very good. and i just had the water pump and tstat replaced, so hopefully this fixes it.

 

Did this to my truck this morning. was super easy. not the heat is HOT! Lots of crap came out.

 

I back flushed my heater core today after reading theses posts. I flushed it 3 times each way from the heater hoses. Then I poured a bottle of Prestone flush in with a funnel and let it soak while I flushed the rest of the coolant system. Then I went back and flushed it both ways 2 more times just using a garden hose. Put it back together filled it up and I have the best heat I have had in years.

 

Welcome to the forum Dagger.

Glad it worked for you.

 

Question. What is the difference between pulling the lines and flushing the heater core, vs doing a radiator flush with the climate control turned to full hot? Shouldn't that run through the heater core too?

 

By disconnecting the line you are getting the full flow through the heater core. Not all the water is routed through the heater core by default. Think about the size of the lines to the core vs. the radiator. It's also why you won't overheat even if the core is clogged, or disconnected.

Turning the **** to high does nothing. Our trucks don't have a heater control valve.