1983 international 9670 coe

Funny you should say that. The only old truck we have that has the old 750-C hanging off the side for show and not plumbed in is a ‘71 359 we repowered with a Big Cam 3 that has the spin on bypass filter on the cooler. Leaving the Luberfiner woulda brought the oil pressure down too low for our liking.

 

The engine will not have a bypass filter. It should have a full flos spin on filter. Baldwin #B96. The bypass Lubrifiner is important on them old motors. It filters 2-1/2 almost 3 gallons extra oil at a finer micron then the fullflow. It also helps keep oil pressure in operating range. The old NH/ NTC’s up until the BC2 could run 80-100 psi when cold. Way to high for bearing longevity. That psi would wash the bearings out like a river when it floods. The bypass kept that in check.

 

What engine is in the truck?
It has to have a full flow filter on the engine somewhere.

 

Full flow should be on RH side oil cooler if an NTC. If it has an NHC could be horizontally mounted on LH side on back of oil pump or remotely mounted on engine block on that side. Either way, It should have a full flow and it will be a big one gallon size filter.

If you need pictures of what I’m describing let me know. I have all three examples in my stable.

 

What i have had success with is Drain, Remove fuel level sender, Plug all hose bungs and vents and put fill cap back on. Pour a gallon of Concentrated ZEP Ring Master toilet cleaner and fill with water all the way to the top thru the sender hole. Let sit and soak for a couple days. Drain again and spend a day flushing and flushing with fresh garden hose water till clean. Get some Diesel services biocide tank Cleaner. (Green label) auto zone and oriellys have it. Pour in whole 32oz bottle with fresh fuel and rock on. That should do the trick.
The Zep is Phosphoric acid. You can use something similar.