Quote:
Originally Posted by ike84
Fan, dude! You've seen inside the belly of the beast! Can you please explain to me how the overflow valve communicates with the main tank/coolant system? I hate not understanding stuff, and I can't find any diagrams or descriptions of what that tube actually does.
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Hey Ike! Yea, I have the Katalog as well and it doesn't go much into it. So far as I have gathered, it can (mis)function like a relief valve. I pulled the old one off of my original tank because it was working fine. It truly just bolts to the top of the reservoir with a small passage that allows it to act like "the highest point of the cooling system" similar to an old radiator cap so you can burp the system properly. However, the gaskets have been known to fail and there were a couple of threads (I cannot find them right now) that showed the valve allowing coolant out onto the top of the tank and that coolant would make it's exit out of the overflow tube. Here's a pic of my old one:
that black plug in the center is rubber and the spring force holds it closed until you use the metal tab on top to open it to evacuate air. Best I can tell from what I've heard, the rubber on the center plug gets tired or, as mentioned earlier, the rubber gasket can fail. The rubber gasket isn't shown in the pic because I disposed of it, expecting to order a new one if I ever needed to swap this valve in.
Let me know if you need more pics. I disposed of the old tank or I'd have taken a picture of the port where the expansion valve connects to the tank as well. Good luck!