Vehicle is a 2000 Sierra with the 5.3.

There is a heat shield on the firewall, mounted right behind the engine, and somehow Im leaking coolant from behind it. I took some picture so that will probably explain it better than words will...


My thought was that is was coming from the AC drainage tube, which it doesnt appear to be doing. I cleaned it up and watched it, nothing.


This is where its actually dripping from, the same place the AC ultimately drips from. When the truck is up to running temp its barely just a drip.


When I turn the truck off, it turns into a steady little stream, all the while watching the AC drainage tube, and still nothing.

I can smell coolant in my AC, just barely. I just dont know how else coolant could be getting behind that heat shield since its not coming from the drainage tube. No puddles on my floor, so I dont know if that completely rules out my heater core or not.

 

If I'm not mistaken, the AC evaporator and your heater core are located in a plastic case housing both of them. The blower motor would draw air through the case, for the heat exchanging. It would make sense that if you can smell coolant in the truck through the vents, it would be leaking at or around the heater core. The heater core is the only thing that is behind your firewall in the cooling system. Hope this helps

 

Right, but its not leaking onto the floor board inside, and its not dripping from the drainage tube, so Im at a loss as to how its even getting behind the shield on the engine side of the firewall.

Looks like I might bypass the heater core and see what it does. I cant see how it can be anything else, but I cant make sense of where its dripping from, so Im still not sure how it could be the core either. Im really not looking forward to the fix I think I have coming..

 

Most heater cores have plastic tubes for inlet/outlet. Sometimes those can crack. Not sure if it matters though, either way it sounds like you'll have to replace the heater core. You could take the shields off and see if it's something you could fix from the outside (at least temporarily).

 

Bypassed the heater core today, and all is well now. Ill add it to my to do list later

 

If you lived up here you'd be fixin' it now.