I've been running my '84 300D on WVO for a couple of years. My system is basically the same as the Greasel setup. For the coolant lines, I put the "coolant out" (hot coolant to WVO tank) tee in the heater hose coming off the back of the block, over the oil filter housing. Return from tank is "tee'd" in right behind the auxilary (electric) water pump on right fender well, across from the turbo. Coolant will circulate through your WVO loop whether you have heat on or not. Flows through the stopped aux pump back into the water pump when heat's off.

Just switched over my "new" 83 SD. Used a 6 port solonoid valve this time so excess diesel returns to stock tank, excess veg oil loops into intake (makes it easier to purge air if you run a tank dry by switching to the diesel side and using the hand pump). I also added a 12V electric fuel pump between WVO tank and the solonoid, switches on when you select WVO. Stock lift pump was having trouble pulling veg oil through the filters.

...I run my WVO through my diesel filter after the lift pump too. Works fine. Boost on both cars turned up to 12.5 psi, Alda opened 1/2 turn. So far so good!

fmb