Changing coolant in a 2004 Tahoe z71 with rear heat

[Red Rider]

Hi have to change the coolant in a 2004 Tahoe z71 with rear heat. In order to properly drain the truck, do i need to do anything to open up valves for heater core (front and rear) prior or during draining?

The FSM says to pull the lower radiator hose off radiator. I have also seen posts about a valve to open on radiator? I looked for valve but did not see anything. Is the lower radiator hose best option?

I picked up an AirLift system for draining the truck. Should make life easier.

 

[treehan77]

Most people don’t use the valve, cause it may break, and you’ll need a new radiator. Some years don’t even have one anyway

 

[Fless]

And there aren't any valves in the heater hoses. Just flush with water (distilled preferred) and you could use some LOW air pressure in the heater hose system to blow out the water. Or not.

 

[Red Rider]

Ok. Thanks. I thought there may be some mechanical valves that would prevent the draining of the cores.

 

[rockola1971]

Ok. Thanks. I thought there may be some mechanical valves that would prevent the draining of the cores.

No valves on or inline with heater cores. The heater cores are always warm (once vehicle is warmed up). Its the blend doors in the ductwork that prevent the vehicle from being heated when you are running the a/c in the summer. The blend door isolates the warm from the cold side (evaporator).

Nothing like the old cars/trucks back in the 80's and before that actually had a vacuum controlled coolant valve that stopped the coolant from going to your heater core. The heater controls on the dash are what sent vacuum to the valve for opening when heat was selected.

 

[Red Rider]

I remember it is better to lift the rear of the truck to drain?

 

[clandr1]

I remember it is better to lift the rear of the truck to drain?

Yes, if you can park nose downhill or lift the rear, that will be better for draining. Similarly, it would help to have the nose uphill/front end lifted when you're burping the system.

 

[SnowDrifter]

They did away with the drain valve on the radiator in 2004, iirc.

For standard service, honestly.... Take off the lower radiator hose, then remove the 2 coolant lines coming off the side of the water pump. THose are your heater core lines

You'll get 80% of the coolant out of the system just by doing that.

It's my opinion that if you need to remove more than that, fill the system up with distilled water, run it for 45 seconds, then drain it again.

 

[Red Rider]

Did it Saturday. It took forever to get the damn clamp off the lower radiator hose. It is a big one. Luckily I had bought a tool that keeps it open for duration of the operation. I did not know about water pump hoses. Keep that for next time. But the coolant was nice a clean coming out. I only changed it because I tested it and the test came out needing to be replaced.

It took forever to drain out. I lifted rear and that helped a bit. the AirLift worked great. sucked the new coolant in in no time after
I confirmed that there were no leaks (held vacuum).

 

[gooffeyguy]

What is the AirLift system?