What is this hose ?

[Zimmermy]

Hello - I have a Chevy express 3500 4.8L V8 year 2009. I'm wondering what this hose is? One end is connected under the radiator cap and the other end seems to be connected just behind the water pump. Do you have any idea what it is? It's leaking at one extremity.

[MountainManJoe]

Welcome to the forum, Zimmermy.

I believe that's the engine block breather/vent, and I think it's there to allow air trapped in the cooling system to escape the engine block.

Here is my crude cooling system diagram for my 2013 5.3L. It should be similar to yours.

In any case, just cut off the leaky end, and re-clamp. If the hose is in too rough shape, (stiff/hardened/split/cracking/no longer supple) or too short, then just replace with hot water hose of equal inner diameter.

[MountainManJoe]

Is it this one? (#2)

GM calls it the "air bleed pipe" in the service manual (link here)

[Zimmermy]

Hi MountainManJoe - clear response thank you ! I'll try that for the hose, but there's a rigid line connected to it that seems to be in bad shape too. That could be the cause of the leak. It doesn't appear on the diagram you sent me. Do you know what it corresponds to?

[MountainManJoe]

OK I re-read the service manual (in the link I posted above), and in fact the part that you show in your photo is the "air bleed pipe". And it is on the drawing I posted. You just need to click on it to enlarge it.

They describe the rubber portion as "vent inlet hose"



Here it is magnified ...

[Zimmermy]

I see it now - thanks for your help !