coolant
 

94 7.3 Idi is there something that needs to be added to the coolant

SCA = supplemental coolant additive. Should be used with a non-ELC coolant, after ph testing as per instructions for the SCA. I think ELC is good for about 3 years then the ph should be checked and a SCA used if required. I use red diesel coolant that is ELC. An alternative is to plumb in a coolant filter/conditioner.

Fleetguard has sca's in it already

What is the proper chemical SCA concentration for diesel engines?
Basically a chemical concentration of 1.5 - 3.0 UPG (Units Per Gallon) should be maintained in your cooling system at all times. How do you achieve that? Well, this depends on the capacity of the coolant system. For a reference, a 1 pint bottle of DCA4 additive is equal to 5 units.

We recommend that you add up to 2.5 UPG if you don't test the SCA as often as you should. Keeping the level this high will help ensure that the level is at least 1.5 UPG. Ideally you should test the SCA every 4-6 months. If you do, then you can keep the level at a lower level of 2.0 UPG. The benefit of a lower level will help prevent the buildup of particles that SCAs often cause. This buildup can become loose or flake off the water jacket walls, and because it can be abrasive, it will cause damage to your water pump or even clog certain parts of the cooling system like the heater core. A preventative measure that can be taken to eliminate this is the use of a coolant filter.

Fleetguard 14.99 gal x 3 gal = 44.97
Evens 50.00 gal x 5 gal = 250.00!

Don't go adding the SCA's to your coolant unless you know it is compatible. If you add the SCA's to standard green coolant, it can gel up creating a real mess in your cooling system. When I got my 93, I had to replace the water pump and radiator so I just bought 8 gallons of the premixed Fleetguard to fill it up.

fleet guard or napa has heavy duty coolant that's real good stuff...