Coolant additive required for 7.3L IDIs.Ford neglected to put that in the owners manual and caused a lot of untimely engine failures.The Cylinder walls are thin since the 7.3 is a bore out 6.9.The walls of the Cylinders bow out durring compression and on the exhaust stroke they snap back to size.The movement causes tiny cavitation bubbles on the outside of the Cylinders in the water jacket.These vacumn bubbles collapse almost instantly and over the years(some as soon as 20K miles,Some 200K miles) the coolant will jackhammer though into the Cylinder.Only way to fix the damage after it has happened is a full rebuild with Boring and sleeving the Cylinders.You can get the stuff at Napa or any diesel place.Dealerships used to have it.There are test strips to check the DCA levels.Make sure before adding any that it is compatible with what is in there.Some brands if you mix them turn into a brown sludge.

 

ok thanks for the advise

 

what is CA ?

 

Stuff you add to the coolant to stop cavitation.Called Diesel Chemical Additive.Also called SCA or Supplimental Coolant Additive.You can buy precharged Coolant at Napa,Straight DCA/SCA you add to your antifreeze,and Test strips.Can't check it via a traditional floater tester.Test strips work better anyway.Shows you the freeze point,Boil point and the SCA/DCA levels.