A navistar engineer told me that the new fuel is messing with the fuel o rings on the 7.3 causing fuel leaks. Usally the fuel drain valve will be first then probally the o rings on the injectors. Just a little bit of info to pass on. Also wondering if anyone else has heard this?

 

It's the "then probably the o-rings on the injectors" part that has me worried.

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Is it the fuel or is it the fact that most of our trucks are going on 5 or 6 years old now?

My drain valve orings started leaking this past summer about 1 month (2 fillups) after they started weaning the ULSD into the supply around here so its hard to say if it was fuel or just old man time. Now if fuel shows up in my coolant in the next few months that is just to much of a coincidence and i have to lean towards the fuel.

BTW: As a part of my weekly maintenance checks I now sniff the coolant.

 

On the other hand, my drain-valve o-rings leaked about two years ago and I replaced them with the buna Danco 90's. Though I now have some Viton rings in hand (thanks to Daryl Newkirk), I don't fix it if it's not broken.

The Danco's have not given me a bit of trouble with the new fuel, and we've had it here for a while.

Who knows?!?!

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