Adding a Coolant Filter to the IDI Cooling System

Many people who aren't used to diesels may not know of the concept of filtering engine coolant. This is something that is almost never seen in passenger vehicles, and is typically deemed to not be necessary. However, it is becoming increasingly common among medium-duty and heavy-duty trucks to see a filter plumbed into the engine cooling system, and some people who own diesel pickup trucks have opted to follow suit. The picture below is of a disassembled coolant filter element after being installed in a Ford diesel pickup. Considering that the orange visible in the picture is the paper that comprises the element, I feel that this picture speaks for itself regarding why, really, EVERY cooling system should have a filter. Without a filter to remove these contaminants, these particles will find a place to reside in the cooling system. This can lead to cooling system issues that include a clogged radiator, a blocked water passage, or even a prematurely failed water pump bearing. The water pump bearing speaks for itself, and the other issues mentioned can lead in reduced cooling system performance, resulting in an overheating engine. After seeing pictures such as this, I decided that adding a coolant filter would be an excellent investment in my truck, particularly since it is relatively inexpensive to acquire all of the parts.

A picture of a different coolant filter element. As the original accompanying text describes it, "Contaminants collected in the coolant filter, about one teaspoon in total. Note how the filter medium appears to be collapsing, and the amount of sludge on the filter medium itself. I could scrape it off with my finger, suggesting it definately was something circulating in the coolant."

Note that both of these pictures come from members on As of this writing, I have not yet needed to replace the filter element in my coolant filter; when I do, I will take the old filter apart and take pictures, so I can give a firsthand account.

There is an added benefit for Ford diesel owners who need to maintain a level of Diesel Coolant Additive (DCA or SCA) in their cooling system in order to prevent cavitation. Many coolant filters come with a certain amount of DCA added in, negating the need to pour liquid additive in. While it is still a good idea to use coolant test strips to keep an eye on the level of DCA in the cooling system, one can simply replace the filter with a fresh filter with the proper amount of DCA already installed when it is time to replentish the DCA level.

I decided to go with Napa Auto Parts' coolant filter kit, part number 4019. The above picture shows everything that came in the kit, along with the filter I chose to use. I opted to use Napa's kit primarily because I wasn't sure how readily available filters would be for other kits, and I live in an area where heavy truck parts sources are relatively sparse. I figured that Napa Auto Parts stores are common enough that getting replacement filters for this filter head shouldn't be an issue. Note the part number on the filter itself. Napa offers five different coolant filters. The part numbers for the filters are 407X, with X being a number between 0 and 4. Each filter has the same dimensions and will fit on the same filter head, but the level of DCA added into the filter is different with the different part numbers, allowing the buyer to get as much or as little DCA as the cooling system needs. The last number of the part number represents how much DCA is built into the filter, with the amounts as follows (from this site):

The 6.9l and 7.3l IDI cooling systems require approximately 8 units of DCA. I chose part number 4070, because I'm using Caterpillar Extended-Life Coolant (ELC), which has an appropiate amount of DCA built in, and I didn't want to over-charge my system. Note also that I did not use all of the parts that came with Napa's kit.



Why Install a Coolant Filter?

Making and Installing Filter Head Bracket

Painting and Installing the Bracket and Filter Head

Plumbing Coolant Hoses


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Page updated November 13th, 2005

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