Can anyone tell me the approximate cooling system capacity of a '91 F-250 with a 7.3 na? Thanks.

 

Don't have your exact truck, but I think about 5 gallons rings a bell. It is alot anyways.

The last time I changed my antifreeze I put in 2 gallons of pure antifreeze and still did not get a 50-50 mix.

 

Welcome to Ford Truck Enthusiasts Bigyellowcat.

I was thinking it was more than 5 gallons....like 26 quarts maybe?

 

29 qts (5qts in overflow bottle). 50-50 low silicate af with distilled water + 2 pints of sca FW 15. Or you a pre charged af.

 

I was going to use Cat extended life coolant, as it does not require regular additions of SCAs, only the addition of an extender at 300,000 miles. The additives deplete very slowly. It is a popular coolant among medium and heavy duty diesels. It uses carboxylates for protection of cooling system surfaces along with nitrites and molybdates, and is phosphate and silicate free. Has anyone heard of any particular problems with that coolant in this engine? One other thing...where is the block drain located? Thanks for replies.

 

Chilton's sez it's 18 quarts. I have a '89 7.3 na F-250 and it's coolant capacity is 18 quarts, as well. I use 2 gallons of antifreeze and one bottle of SCA.