Reddit reviews WIX Filters - 24019 Heavy Duty Filter Mounting Base, Pack of 1

The IDI's have really really high compression, much more than DI diesels and when they fire the cylinder walls throb. This is especially the case with the thinner walled 7.3L IDI, the 6.9L has less issue with it.

What happens is the coolant gets kicked away from the walls of the coolant passages. The engineering word for that is cavitation, it means that there a little bubbles, liquid free zones in the coolant passages. Shake a capped water bottle and you'll see what I mean.

Over time, because of exposure to air they can rust and form a pin hole leak from the coolant passage into the cylinder, at which point the engine block is ruined.

Cavitation especially happens if you have a weak coolant to water mixture, a failed or improper (too low) pressure rad cap, and if the truck is used for lots of little trips and not allowed to get up to operating temperature.

International's solution to this was to add a phosphate coating to the coolant. A "Supplemental Coolant Additive." It coats everything, and stops the rust.

Problem is it eventually flakes off, and the little particles can kill your water pump bearings.

IH changed the water pump for one that has a filter built into it, while Ford just recomened getting the coolant changed at regular intervals and to add SCA when needed.

Myself, and a lot of other IDI owners don't care for this arrangement so the coolant bypass filter is a pretty popular mod. Just goes in parallel with the heater core, and the filters come pre charged with the SCA. Extends the change intervals indefinitely.

filter

plumbing

Mine is a little more complicated than it needs to be. I put a valve that lets me run 100% heater flow through the filter for extra cleaning before I swap it out.

A lot of the kits offered by diesel shops are way over priced, Wix makes the filter head I used filter head for 35$.

It's about the best mod you can do to an IDI.


edit: one last thing, I think, but am not 100% sure than you can also solve this by switching to a waterless polypropylene glycol coolant. Note this is not the same as modern OEM coolants. They're the industrial ones the ones that are billed as being much less toxic. They also cost a fair bit more per gallon.