QSB After Cooler O-Rings

[Scott Lambert]

I am about to service my QSB 5.9 380 after cooler. Trouble is I am confused about whether to use the thick or thin O rings. From the pictures in your article “B Series After cooler O-Ring Identification” I should use the thin ones, but the Cummins spare parts website shows thick rings for my engine serial number. My boat was built in 2008, engine serial number 46824262. Any Ideas?

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[Scott Lambert]

Thanks Tony, you are right as always and the spare parts web site is wrong. I have now pulled my after cooler apart and my O rings are definitely the thin ones.
The story is that I serviced my after cooler about 18 months ago but I noticed I was getting a bit of grease bleeding out under the end caps, I also noticed a tiny bit of corrosion which is visible in the photo just under the water outlet. It occurred to me that the turbo air pressure may be pushing the grease out and that maybe my O rings hadn’t sealed as well as they should have. When I saw that the Cummins spare parts website specified the thick rings I thought that might be the cause.
Seems I was panicking about nothing (pretty standard for me), my after cooler is on the bench now and in very good shape. So my question now is is it usual to get a bit of grease bleeding through under the cap?

[Tony Athens]

You cannot go by the engine serial number.. It all depends on the size of the “cap bevel”..

“O-ring” squash in in the 1mm range..

ps://www.sbmar.com/articles/b-series-aftercooler-o-ring-identification/

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