Custom Coolant Filter on my IDI F250

My 1992 F250's radiator failed and (as per the link) I replaced the radiator and installed a custom coolant filter at the same time. I used parts ordered from International, and plumbing parts from a local agricultural pump and plumbing supply. All connections were sealed with blue RTV silicone sealant for its ideal compatibility with coolant and its high grip strength. The output side of the filter is the one weak point in the design, but I hope that tightening the connections well, using brass to inhibit corrosion, and using plenty of RTV will keep it from disconnecting itself. I hoped to use street ells at the filter head, but there were none available in brass and I ended up with nipples and ells.

Coolant Filter Overview Coolant Filter Detail

I covered this in the blog entry already, so here's the story in short: The water pump takes water from the block and sends it to the radiator. Some of it flows out of the side of the block and heads to the heater core. Water returning from the heater core enters the water pump. On later models of IDI like mine, there is a bypass return on the return line which flows to the bottom of the radiator, for return to the engine through the radiator lower hose.

6.9 and 7.3 liter international/ford IDI diesel coolant flow diagram

Restriction of flow through the heater core causes a pressure drop on the return side of the heater circuit. The coolant filter is installed between the supply and return hoses for the heater core, and this pressure differential causes some fluid to pass through the filter. This is a "bypass" installation, meaning that only a small amount of the fluid sent to the heater core passes through the filter. Ball valves in the circuit permit changing of the filter without draining the coolant.