Update: Today I started poking around testing things and I believe I found the problem. I took off the duo-valve and it appears to be stuck shut. I don't have a t-10 handy to take it apart so I have to run to the store and buy one.

Details later...

OK, it's now about a quarter to 5 PM and I finally have heat!

This morning it was about 65 deg here at 8 AM so I swore to myself that I would fix the heat before it gets cold again.

I started with the aux water pump. It was running but I took it off to make sure everything was in place and nothing was broken inside. Turns out it's a very robust design with a magnetically coupled impeller and there's not much chance it's not pumping if you can hear it running. However, the impeller can be jammed with a foreign object and the motor will still sound like it's running fine.

Just for giggles, I used the "rest" button and ran the pump with the hose off that runs to the engine. Curiously, it did not produce the geyser of water that I would have expected, rather it just sort of bubbled over the edge.

Next, I moved on the the duo-valve. Upon opening the bottom part, I imediately saw the problem. The two "floating" brass plungers were fused to the rubber seals, effectively blocking 99% of the water flow. I dug a little further into the valve and began to find large chunks of torn rubber as well as most of the other rubber seals displaying signs of dry rot.

I believe what happened is that during the 3-4 months the car sat idle, the water level was somewhat lower due to me removing the rear water feed line. This allowed the duo-valve to dry out and the rubber seals to disintegrate.

Anyway, it's working now temporarily and I'll be ordering a rebuild kit if it's available or possibly, just the seals.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250