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TSB 07-01-96

Low Heater Output In Cold Temperatures

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Date: Feb. 3,1997

Models: 1994 - 1997 (BR) Ram Trucks

NOTE: THIS BULLETIN APPLIES TO RAM TRUCKS EQUIPPED WITH THE 8.0L ENGINE BUILT BEFORE OCTOBER 1, 1996 (MDH 10-01-XX).

Symptom/Condition:

Low heater output during cold ambient conditions.

Diagnosis: 

NOTE- THE FOLLOWING DIAGNOSIS MUST BE PERFORMED WITH AMBIENT TEMPERATURES BETWEEN 20° F TO 32° F.

Using the Scan Tool (DRB III) and appropriate Diagnostic Procedure Manual or Mopar Diagnostic System (MDS), verify that all engine systems are functioning correctly. If Diagnostic Trouble Codes (DTC's) are present, record them on the repair order for future reference and repair as necessary. Drive the vehicle a minimum of ten minutes while monitoring the Engine Coolant Temperature (ECT) sensor with the DRB III using the SENSOR display screen. If the ECT sensor temperature reading does not rise to or remain above 180° F. during the ten minute road test, perform the Repair Procedure.

Parts Required:
Qty. Part No. Description
1 53006047 Thermostat Housing
1 55035944 Heater Supply Fitting
1 53005868AB Thermostat Housing Gasket
1 53021074AB Water Pump Assembly
1 53021072 O-Ring, Water Pump
AR (1) 04318034 Mopar Thread Sealant With Teflon

Repair Procedure: 

This bulletin involves replacing the thermostat housing and water pump assembly with revised parts.

NOTE: ALL 1994 8.0L RAM TRUCKS AND 1997 8.0L RAM TRUCKS BUILT BEFORE OCTOBER 1, 1996 ARE EQUIPPED WITH THE REVISED THERMOSTAT HOUSING AND GASKET. THESE VEHICLES WILL REQUIRE THE REVISED WATER PUMP ASSEMBLY TO BE INSTALLED ONLY.

1 . Record all radio station presets.

2. Disconnect and isolate the battery negative cable.

WARNING: DO NOT LOOSEN THE RADIATOR CAP OR DRAIN COCK WITH THE SYSTEM HOT AND PRESSURIZED. SERIOUS BURNS FROM THE COOLANT COULD RESULT.

3. Drain the coolant from the cooling system into a clean container for reuse.

4. Remove the upper radiator hose from both the radiator and thermostat housing.

CAUTION: CONSTANT TENSION HOSE CLAMPS ARE USED ON MOST COOLING SYSTEM HOSES. WHEN REMOVING OR INSTALLING, USE ONLY TOOLS DESIGNED FOR SERVICING THIS TYPE OF CLAMP, SUCH AS SPECIAL TOOL 6094. SNAP-ON CLAMP TOOL HPC-20 CAN BE USED FOR LARGER CLAMPS. ALSO, A NUMBER OR LETTER IS STAMPED INTO THE TONGUE OF CONSTANT TENSION CLAMP. IF REPLACEMENT IS NECESSARY, USE ONLY ORIGINAL EQUIPMENT CLAMPS WITH A MATCHING NUMBER OR LETTER.

WARNING: ALWAYS WEAR SAFETY GLASSES WHEN SERVICING CONSTANT TENSION CLAMPS.

5. Remove the washer hose from the washer pump and drain the washer fluid from the reservoir into a clean container for later use.

6. Unplug the wire harness connectors from the washer pump and the washer fluid level sensor (if equipped) (Figure 1).

7. Pull the reservoir upwards and away from the radiator fan shroud to disengage the mounting tabs of the reservoir from the mounting slots in the shroud.

8. Remove the four fan shroud mounting bolts at the radiator (Figure 2). Do not attempt to remove the shroud from the vehicle at this time.

9. Remove the fan/fan drive assembly from the water pump by using a 36mm fan wrench (Snap-on Special Tool SP346) and turning the mounting nut counterclockwise (as viewed from the front) (Figure 3). Threads on the fan drive are right-handed. Place a pry bar between the water pump pulley bolts to prevent the pulley from rotating.

  

10. Remove fan blade/fan drive and fan shroud as an assembly from the vehicle.

CAUTION: DO NOT PLACE THE THERMAL VISCOUS FAN DRIVE IN THE HORIZONTAL POSITION. IF STORED HORIZONTALLY, THE SILICONE FLUID IN THE VISCOUS DRIVE COULD DRAIN INTO ITS BEARING ASSEMBLY AND CONTAMINATE THE BEARING LUBRICANT.

11. Relax the spring loaded automatic belt tensioner by rotating the tensioner counterclockwise (as viewed from the front) (Figure 4) and then, remove the accessory drive belt.

12. Remove the four water pump pulley hub bolts (Figure 3) and remove the pulley from the vehicle.

13. Remove the lower radiator hose at the water pump.

14. Remove the heater hose at the water pump fitting.

15. Remove the seven water pump mounting bolts (Figure 5).

  

16. Loosen the clamp at the water pump end of the bypass hose. Slip the bypass hose off the water pump while removing the water pump from the vehicle and discard the water pump assembly. Do not remove the clamp from the bypass hose.

CAUTION: DO NOT PRY BETWEEN THE WATER PUMP AND THE TIMING CHAIN CASE/COVER. THE MACHINED SURFACES MAY BE DAMAGED RESULTING IN LEAKS.

17. Clean the water pump-to-timing chain case/cover o-ring mating surface.

18. Apply a small amount of petroleum jelly to o-ring (pin 53021072) and install the 0- ring onto the water pump.

19. Guide the water pump fitting into the bypass hose and install the water pump onto the engine. Install the seven water pump bolts (Figure 5). Tighten the water pump mounting bolts to 40 Nm (30 ft. lbs.) of torque.

20. Position bypass hose clamp to bypass hose.

21. Verify that the water pump impeller does not contact the timing chain case/cover by spinning the water pump shaft by hand.

22. Connect the lower radiator hose to the water pump and install the hose clamp.

23. Connect the heater hose and hose clamp to the heater hose fitting.

24. Install water pump pulley. Tighten the pulley mounting bolts (Figure 3) to 22 Nm (16 ft. lbs.) of torque. Place a pry bar between water pump pulley bolts to prevent pulley from rotating.

25. Relax tension from automatic belt tensioner by rotating the tensioner counterclockwise (as viewed from front) and install the drive belt.

CAUTION: WHEN INSTALLING THE SERPENTINE ACCESSORY DRIVE BELT, THE BELT MUST BE ROUTED CORRECTLY. IF NOT, THE ENGINE MAY OVERHEAT DUE TO THE WATER PUMP ROTATING IN THE WRONG DIRECTION. REFER TO FIGURE 6 AND FIGURE 7 FOR CORRECT BELT ROUTING.

  

26. Remove the two intake manifold to generator support rod mounting bolts and remove the support rod (Figure 8).

27. Disconnect the wiring connectors at both of the sensors located on the thermostat housing and the ground from the temperature gauge sending unit.

28. Tie strap the ground wire and connector to the main wiring harness.

29. Remove the heater hose clamp at the thermostat housing heater supply fitting. Remove the heater hose.

30. Remove the six thermostat housing mounting bolts (Figure 9). Remove the thermostat housing and discard it.

  

31. Remove the coolant temperature sensor and temperature gauge sending unit from the thermostat housing noting the location of each sensor (Figure 9).

NOTE: THE TEMPERATURE GAUGE SENDING UNIT HAS A SINGLE TERMINAL IN THE CONNECTOR AND A GROUNDING TAB ON THE BODY OF THE SENDING UNIT.

32. Apply Mopar Thread Sealant With Teflon (p/n 04318034) to the threads of the coolant temperature sensor and the temperature gauge sending unit.

33. Install the sensor, sending unit, and new heater supply fitting (p/n 55035944) into the revised thermostat housing (p/n 53006047) (Figure 10). Tighten each sensor to 3.5 Nm (30 in. lbs.) of torque. Make sure the coolant temperature sensor and temperature gauge sending unit are positioned into the new housing exactly as they were on the old housing and noted in step 31. Tighten the heater supply fitting to 16 Nrn (12 ft. lbs.) of torque.

NOTE: FOR PROPER OPERATION OF THE TEMPERATURE GAUGE SENDING UNIT AND THE COOLANT TEMPERATURE SENSOR IT IS IMPERATIVE THAT THEY ARE INSTALLED IN THE PROPER LOCATIONS IN THE THERMOSTAT HOUSING.

34. Clean thermostat mating area of the intake manifold. Install gasket (p/n 5300586BAB) onto intake manifold and over thermostat (Figure 10).

35. Install thermostat housing and the six thermostat housing-to-intake manifold bolts.

36. Tighten bolts to 25 NM (18 ft. lbs.) of torque.

CAUTION: HOUSING BOLTS SHOULD BE TIGHTENED EVENLY TO PREVENT DAMAGE TO HOUSING AND TO PREVENT LEAKS.

37. Connect heater hose to the heater supply fitting and install hose clamp.

38. Connect wiring to the coolant temperature sensor and temperature gauge sending unit.

39. Install support rod.

40. Position fan shroud and fan blade/viscous fan drive assembly to vehicle as a complete unit.

41. Install fan blade/viscous fan drive assembly to water pump shaft.

42. Install fan shroud to radiator. Tighten bolts to 6 NM (50 in. lbs.) of torque.

43. Install the washer reservoir onto the radiator fan shroud.

44. Connect the washer hose, washer pump wire harness, and washer fluid level sensor (if equipped).

45. Refill the washer fluid reservoir with washer fluid.

46. Install the upper radiator hose and hose clamp to the thermostat housing.

47. Fill cooling system. Refer to the 1997 Ram Truck Service Manual (Publication No. 81 -370-71 08), page 7-34 for information regarding coolant refilling procedures.

48. Connect negative battery cable to battery.

49. Start and warm engine. Inspect cooling system for leaks.

50. Reprogram the radio station presets to the values recorded in step 1 and reset the clock.

Notes: 

Policy:    Reimbursable within the provisions of the warranty.

Time Allowance:
Labor Operation No:    
07-50-01-91 Replace Water Pump Assembly, 1994 And 1997 Ram Trucks 1.0 Hrs.
07-40-05-93 Replace Water Pump Assembly And Thermostat Housing, 1995 - 1996 Ram Trucks 1.7 Hrs.

Failure Code:
P8 New Part

 


Thanks to Bob Bergevin and Barry Drodge for supplying this TSB information

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This page was edited on: May 3, 2004