3500 4x4 Pickup L6-359 5.9L DSL Turbo (1996)
Vacuum Pump: Customer Interest
A/C - Vacuum System Contaminated By Engine Oil
NO: 24-16-96
GROUP: Heater & A/C
DATE: Oct. 11, 1996
SUBJECT:
Vacuum System Contaminated By Engine Oil
MODELS:
1995-1996 (BR) Ram Trucks
NOTE:
THIS TECHNICAL SERVICE BULLETIN APPLIES TO VEHICLES EQUIPPED WITH THE 5.9L CUMMINS DIESEL ENGINE WITH
ENGINE SERIAL NUMBERS (ESN) 56230585 THROUGH 56293178 OR 45232867 THROUGH 45360437. THESE ENGINES WERE
INSTALLED IN VEHICLES BUILT BEFORE JUNE 1, 1996 (MDH 06-01-XX).
SYMPTOM/CONDITION:
When the vacuum supply is contaminated by engine oil, any or all of the following may be customer concerns.
^
Inoperative HVAC controls (i.e. airflow through defroster ducts only)
^
Oil dripping from HVAC control head or the actuators onto the floor mat or carpet
^
Speed control inoperative, slow to engage, or will not remain at a constant speed
^
Unable to engage/disengage four wheel drive
DISCUSSION:
Some Ram Trucks equipped with the 5.9L Cummins Diesel engine were produced without a check valve on the vacuum pump. Without the check valve,
oil may enter the vehicle's vacuum system during extended engine idling conditions, accumulating in areas of the vacuum harness that are lower than the
suction port on the vacuum pump. With the engine OFF, this accumulation of oil can be pulled through the vehicle's vacuum system, contaminate
vacuum actuated devices, and eventually cause the device to malfunction.
DIAGNOSIS:
Any customer concern related to the previous Symptoms/Conditions should have the ESN inspected to verify whether or not the engine is within the
suspect range. The ESN can be found on the Engine Data Plate, located on the left side of the timing cover housing, next to the oil fill tube (Figure 1).
The ESN (also known as the Engine No) is located to the right of the Timing TDC Specification.
If the ESN is within the suspect range, perform the following Repair Procedure. Also, a complete visual inspection of the vacuum system should be
performed. Visually inspect the following vacuum actuated systems for contamination of engine oil at each vacuum port.
