Fuel in Coolant, Cummins TSB170004

[Hamish]

Thanks for letting me know how long yours lasted for. Mine is a CM870, a newer model engine is modified with a special ring and tool, a different TSB, 170002 if I recall. I didn't need any special tools to do this one. Didn't take that much longer than just doing an overhead set. I think they changed the o-ring composition to something that withstands coolant as originals weren't intended to be exposed to coolant if the cups would have held out. My o-ring shop tested the composition of the original o-rings, likely Viton, and I'm guessing the blue upgraded o-rings are low-temp Viton which is more resistant to coolant, or maybe something even fancier.