Problem with B43M and B48M Onan engine dipsticks [Archive] - Case Colt Ingersoll Lawn and Garden Tractor Forum

View Full Version : Problem with B43M and B48M Onan engine dipsticks

Bob MacGregor
06-28-2020, 06:49 PM
Hi Troops,
As time passes, the dipsticks on these engines wear in a critical spot. These dipsticks, Onan P/N 123-1292 have been discontinued by Cummins/Onan and new ones are in very short supply!
The problem with these dipsticks is that the slot in the metal cap and the stampings on the dipstick that hold the cap in position wear against each other and in time the cap and the rubber plug slide up the dipstick. This causes a very incorrect engine oil level reading!
Some of you are aware of the correct procedure of installing this dipstick which is to push on the cap with two fingers when putting back into the tube, but some of you push on the loop on the stick which is wrong. The rubber plug on the stick pops into place to hold the dipstick in place. The reason for this is that these engines have a high crankcase pressure during part of the cycle in addition to splashing oil up into the tube while running.
These dipsticks can be repaired, I don't repair them but there is a member that does repair them and I will contact him to ask his permission to post his name.:geek: