Just bought another 7.3 excursion. This summer I will flush and put in elc. In the meantime, it is a bit low and what should I top it off with? It looks green, seller told me it isn't original, and had been a bit low like that for some time. I have some of the basic 50/50 premixed but not sure if that is diesel rated or compatible with what is in there.

 

Without the MY or Build Date; you'll get the long answer to digest..

The cooling system on any diesel has special concerns. It's possible for the coolant to cavitate--produce tiny bubbles--that can with time because pin holes through the cylinder walls from the water jackets. For this there is an additive; Ford P/N FW-15 or FW-16, Fleetguard P/N DCA4; that needs to be maintained in the coolant. Generally this means installing 8 to 10 oz. of the additive to the cooling system every 15000 miles. Another method is to monitor the cooling system with Fleetguard's DCA4 test kit P/N CC2602 or CC2602A.

This measures the level of DCA4 in the system, then you add the amount of SCA/DCA as required to reach a nitrite level of 1.2-3.0 PPM. The cooling system should be drained (and flushed if you live in an area with specially alkaline water) and refilled with a fresh 50/50 mix of coolant/distilled or demineralized water and one pint of the additive for every two gallons of coolant/water at 30,000 miles. Use only an ethylene glycol-based coolant, preferably low-silicate.

•Ford or Motorcraft Premium Antifreeze •Texaco Antifreeze/Coolant •Texaco Antifreeze/Coolant Pre-diluted 50/50 •Zerex 5/100 (white bottle) Antifreeze/Coolant •Zerex Ready To Use Antifreeze/Coolant (premixed 50/50 with demineralized water) •Zerex Heavy Duty Precharged Formula •Shellzone Premium Quality Antifreeze •Prestone Heavy Duty (black bottle) Antifreeze/Coolant with SCA •Fleetguard Complete EG--precharged at 1.5 units/gallon DCA4
Also available premixed 50/50 with water with the same DCA4 level •Pyroil Heavy-Duty Antifreeze/Coolant--Low Silicate •Peak Full Force or Advance •Fleet Charge Antifreeze/Coolant--precharged with Pencool •Wal-Mart Super Tech2002 model year trucks use any of the above if your truck came filled with green coolant.

If it came from the factory with yellow coolant, only use Motorcraft Premium Gold Long Life Antifreeze, Zerex G05 (gold bottle), Peak Global Lifetime (gold bottle) or Peak Extended Life CF-EXL (silver bottle). These coolants are fully-formulated using hybrid organic acid technology (HOAT) and do not require SCA/DCA. Recommended service interval with the gold coolant is 5 years or 100,000 miles. Test the gold coolant periodically for pH balance and freeze protection.

* Trucks originally filled with Gold coolant: All 2002 F-Series built at the Kentucky Truck Plant (VIN 11th digit "E") 2002 F150-550 built in Cuautitlan (VIN "M") from 2-4-02 2002 F650/750 built in Cuautitlan from 1-28-02 All Econolines built from 7-15-02 Ford has approved using the gold HOAT coolants in their vehicles as far back as the 1999 model year, providing the cooling system has been thoroughly flushed to remove all traces of the green coolant.

If regular tap water is used instead of distilled or demineralized water, the recommended service interval is only 50,000 miles. Ford does not recommend using propylene glycol-based coolants in any of their vehicles, or "universal" coolants that claim to be a replacement for any color antifreeze. They also have not approved the use of any organic acid technology (OAT) extended life coolants (ELC) in the Powerstroke cooling system.
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BTW, this is the procedure I used to replace the coolant last time and it worked perfectly! It can be found on this site. I didn't have the guts to try any new type of coolant so I went with Ford's (undiluted) Gold, 4 gallons of it and of course, lots of distilled water to flush and finally mix with the new Gold coolant.




Gooch's Radiator Flush Procedure