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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 989
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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May Cat 311B has hydraulic fluid in the motor oil. Can you

Customer Question

May Cat 311B has hydraulic fluid in the motor oil. Can you advise what may be causing this?
JA: What is the complete model and serial number of your machine?
Customer: I don't have it with me.
JA: Are you fixing this yourself? What have you tried so far?
Customer: At first we thought it was fuel, we installed a new injector pump, e
JA: Anything else you want the construction mechanic to know before I connect you?
Customer: sorry...hydraulic pump has been rebuilt. if I use it hard it will make 1/4 to 1/21/2 to a full gallon of oil a day. we pulled the starter and bell housing is all dry. We are being told it is going through the rear main seal of the motor, my mechanic wants to replace the pump.
Submitted: 2 months ago.
Category: Construction and Road Equipment
Customer: replied 2 months ago.
We have put in new injectors, rebuilt the hydraulic pump, pulled the starter and it is dry behind there. If I work the machine hard I can make 1/2 to a full gallon of fluid in the motor oil and have to drain it. I have been told it might be the rear main seal.
Customer: replied 2 months ago.
Hello???
Expert:  Bradley Martin replied 2 months ago.

The only place hydraulic oil can get into the engine is through the hydraulic pump through the rear main seal there is nowhere else it could gain hydraulic oil from. How do you know it is gaining hydraulic oil?

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