Last summer my tower started to leak. Everyone knows the plastic distribution tower / manifold weakens with age. The 2 wd tower is different in size and shape but same thing happens to it.
What I posted to the vanagon mailing list:
A few months ago I swapped in an aluminum version of the stock plastic coolant distribution manifold. The 2wd and Syncro versions differ in shape but not in function.
I’d always wanted to do this but what got me off my duff was my manifold had the additional feature of a temp sensor plug in one end. This is for the optional webasto aux heater that warms the coolant and thus the heater box. It was fairly common on Canadian spec Syncro.
The temp sensor is very much like a temp II sensor in that it’s a push in device with an o ring and retaining clip.
The o ring on mine failed and leaked coolant. Temp fix was new o ring. The better fix was the aluminum manifold which was easier and less messy to install than I feared.
Bottom line is, if you have the webasto aux heater in the engine compartment of your Syncro, or if you had one and forgot about the temp sensor , check the sensor O ring.