C15 coolant flow

You need to shut off both ends to stop it from leaking. No harm in blocking both ends of the bunk lines, the cab has separate lines and will still work, just make sure you get the right valves for the bunk.

Our drivers always get confused about this. We spray painted the cab valves white, the bunk valves black and the coolant filter valves red. When a driver calls and says his bunk heater is leaking, I can tell him to close the black valves.

 

If your APU circulates coolant through the heater core hoses, make sure that you don't block them off. The APU pump still needs a complete circuit to flow. I don't know how it's plumbed. If it's in series with the bunk heater core, then you'd need to bypass only the heater core by connecting the hoses together with a hose barb.

 

From the looks of things his APU is plumbed in series with the heater core hoses. Look on the outside of the frame rail. In pic 1 you can even see 2 lines going into the 1 fitting both with shutoffs. They put shutoff valves past it to where he can close off the heater core without closing off flow to the APU. The hoses and locations are exactly like what's on mine - excepting the APU lines.

 

My cascadia has a apu. Leaking minor. 2 valves. So if i close the valves the apu coolant should shut off right

 

On a c15 accert, can i shut off both bunk and cab heater cores, say for the summer? If so, do I just shut of the valves at rhe waterpump?

 

Yes.
Why would you want to shut down the lines in summer?
There will always be an occasion where you need some heat.
The blend door in my heater box once failed in the open position and supplied continuous heat in summer. I've tried to control the heat with the shut off valves. It was a nightmare. Opened the hood maybe ten times a day.

 

You can. Shutting off the valves by the water pump will stop flow through them, so the heater cores will not get hot. Newer trucks have much better HVAC systems, so it's really not needed. At least I never noticed much of a difference, not like older trucks anyway. It's a good idea to close and open all the valves once in a while, so you know they work and are east to shut off to stop a leak. Our 379 Pete's with Acerts have the rear valves in a very crappy location behind the turbo, not something you want hard to turn on a hot engine, so I close them and open them on oil changes to keep them working good.

 

05 Columbia. Coolant leaking from bottom of heater core? Below bunk. No shutoff valves. Can I bypass by tying the two lines together?