A/C - Vacuum System Contaminated By Engine Oil
NO: 24-16-96GROUP: 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.
HVAC Control Head
HVAC Vacuum Harness
Floor Duct Door Actuator
Vent/Defrost Door Actuator
Fresh Air Door Actuator
Engine Vacuum Harness
Speed Control Servo
Speed Control Servo Vacuum Reservoir
Speed Control Servo Vacuum Harness
Four Wheel Drive Mode Switch
Four Wheel Drive Axle Disconnect Motor
Axle Disconnect Motor Vacuum Harness
Any portion of the vacuum system contaminated by engine oil should be repaired or replaced. Refer to the 1996 Ram Truck Service Manual (Publication No. 81-377-6108),
Group 24 for servicing of the HVAC vacuum system, Group 8H for servicing of the speed control system, and Group 3 for servicing of the front axle motor disconnect.
NOTE:
ALL VACUUM ACTUATED COMPONENTS MUST BE INSPECTED FOR CONTAMINATION FROM ENGINE OIL AND PROPERLY SERVICED PRIOR TO RETURNING THE VEHICLE TO THE CUSTOMER.
PARTS REQUIRED:
1 04883793AA Check Valve Package
REPAIR PROCEDURE:
This bulletin involves installing an external check valve onto the vacuum pump and replacing the main vacuum harness.
1. Disconnect the 1/8 in. diameter HVAC vacuum supply hose from the in-line vacuum "T" connector on the main vacuum supply hose.
2. Remove and discard the 3/8 in. main vacuum supply hose.
3. Remove the vacuum nipple at the vacuum pump and discard the nipple.
4. Install the check valve onto the vacuum pump. Tighten the check valve to 52 Nm (38 ft. lbs.) of torque.
5. Install hose clamp onto main vacuum supply hose. Install main vacuum supply hose onto the vacuum pump external check valve. Properly position and tighten the hose clamp.
NOTE:
POSITION IN-LINE "T" CONNECTOR SO THAT THE HVAC PORT IS POINTING UPWARD BEFORE TIGHTENING THE CLAMP.
6. Route the main vacuum supply hose over the top of the power steering hoses and tie strap the vacuum harness to the engine wiring harness located near the rear of the fuel injection pump.
7. Install a hose clamp onto the main vacuum harness and connect the main vacuum harness to the power brake booster check valve. Tighten the hose clamp.
8. Connect the 1/8 in. diameter HVAC vacuum supply hose to the in-line vacuum "T" connector on the main vacuum harness.
POLICY: Reimbursable within the provisions of the warranty.
TIME ALLOWANCE:
Labor Operation No: 24-50-47-92 0.5 Hrs.
FAILURE CODE: P8 - New Part