Worn or incorrectly installed belts and tensioners, as well as a misaligned pulley, can cause the belt to come off.
This can cause a reduction in the speed of the coolant pump and/or the fan, leading to engine overheating.
When diagnosing engine cooling system faults, the radiator cap/expansion tank cap is usually given the least attention.
The cooling system uses a sealed radiator cap to prevent the coolant from boiling.
Incorrect selection of the cap or a faulty cap can also lead to coolant leakage and engine overheating.
The technical specifications of the radiator cap are given in the documentation for the complete equipment.
The air passing through the radiator fins due to the vacuum created by the fan draws heat from the coolant, which is pumped through the radiator by the water pump.
Foreign objects (pieces of paper, dry grass, fabric fibres, dust, etc.) can become trapped between the fins, obstructing the passage of air. This reduces the efficiency of the radiator.
The radiator must be checked periodically for bent or broken fins and coolant leaks.
If the fan is belt-driven, belt slip can reduce the fan speed and reduce the efficiency of engine cooling.
The problem may also be related to a fault in the automatic belt tensioner.
Check the bearings in the fan hub and the other pulleys and make sure they do not cause excessive vibration and belt slip.
Insulating covers can be used to reduce engine warm-up time and help retain engine heat in cold-climate regions.
Insulating covers should cover only part of the radiator at the front, leaving space for air passage.
If part of the front of the radiator is not left open to the air flow, or the insulating covers are not removed when the ambient temperature rises, this can lead to engine overheating.
If the radiator is combined with a charge air cooler, fitting a cover without an opening will result in poor charge air cooling.
Do not fit homemade cardboard covers, as the degradation products of such insulation will cause heavy contamination of the radiator and charge air cooler.
If the vehicle is equipped with thermostatically controlled shutters, check the coolant temperature at which the shutters open and close.
Compare the result with the value indicated on the shutter control device.
Cummins recommends opening the shutters when the coolant temperature reaches 85 °C.
If the engine is fitted with a thermostatically controlled cooling system fan clutch, check the coolant temperature at which the fan clutch engages.
Cummins recommends engaging the fan when the coolant temperature reaches 96 °C.
If a viscous fan clutch is installed on the engine, check the coolant temperature at which the fan engages.
Note: some models of viscous fan clutches may have electronic control.
If the air temperature reaches the set level determined by the temperature setting of the sensor used, the thermosensitive element moves the actuator, which allows the viscous fluid to engage the fan drive and increase its speed.
Cummins recommends engaging the fan when the coolant temperature reaches 96 °C.
Removal and installation of the coolant pump
Caution! If there is a permanent coolant leak, replace the coolant pump.
- Drain the coolant.
- Remove the accessory drive belt.
- Unscrew the 8 mounting bolts and remove the coolant pump. Tightening torque: 8 N·m.
Fig. 6. Removal of the coolant pump.
Clean the surfaces of the coolant pump.
Installation of the coolant pump is carried out in the reverse order of removal.
Inspection
- Make sure the coolant pump impeller has no scoring or damage. If damaged, the impeller must be replaced.
- Make sure the coolant pump seal is not damaged. If damaged, the seal must be replaced.
Thermostat
Note: the thermostat housing is part of the intake manifold. If the thermostat housing is damaged, the intake manifold must be replaced.
Pre-removal check
After closing the thermostat for 1 minute with the engine running, do the following:
- connect the diagnostic tool to monitor the coolant temperature.
- Disconnect the radiator hose from the cooling system outlet union.
- Fit the hose to the cooling system outlet union, tighten the clamp and lower the free end of the hose into a measuring container.
Fig. 9. Fitting the hose into the measuring container. - Start the engine and warm it up at rated speed for one minute while monitoring thermostat opening.
- If the thermostat opens during this check, repeat it. Permissible coolant temperature: 38 °C.
- Stop the engine and measure the coolant volume in the measuring container.
If the volume of fluid collected exceeds the permissible value, the thermostat must be replaced.
Permissible volume: 100 cm³.
Removal and installation of the thermostat
- Disconnect the lead from the battery negative terminal.
- Drain the coolant.
- Unscrew the mounting bolt, remove the cooling system bypass union and the O-ring.
Fig. 11. Removal of the bypass union. - Disconnect the upper radiator hose from the cooling system outlet union.
- Unscrew the mounting bolts of the cooling system outlet union.
- Remove the cooling system outlet union.
Fig. 12. Removal of the outlet union. - Remove the thermostat.
Fig. 13. Removal of the thermostat.
Installation of the thermostat
- Install the cooling system outlet union and tighten the mounting bolts. Tightening torque: 7 N·m.
- Connect the upper radiator hose to the cooling system outlet union.
- Install the cooling system bypass union:
- install a new O-ring;
- install the cooling system bypass union and tighten the mounting bolt. Tightening torque: 24 N·m.
- Fill with coolant.
- Connect the lead to the battery negative terminal.
- Start the engine and check for leaks.
Thermostat inspection
Note: as a rule, the thermostat housing bears numbers indicating the valve opening start temperature.
Clean the contact surfaces using an abrasive sponge.
Make sure the thermostat seal is not damaged. If damaged, the thermostat must be replaced.
Check the thermostat opening temperature.
Immerse the thermostat and thermometer in a container of water and heat slowly.
Note: the thermostat and thermometer must not touch the side walls of the container.
Check the thermostat valve opening temperature.
- Opening start temperature: 79–83 °C.
- Fully open temperature: 94 °C.
Check the cooling system bypass union:
- clean the union with soapy water;
- dry it with compressed air.
Clean the O-ring grooves.
Make sure the O-ring groove is not damaged. If damaged, the bypass union must be replaced.
Removal and installation of the coolant heater
- Disconnect the lead from the battery negative terminal.
- Drain the coolant.
- Disconnect the wiring from the coolant heater.
- Disconnect the coolant heater. Tightening torque: 55 N·m.
Fig. 19. Removal of the coolant heater.
Apply a layer of sealant to the heater thread. Sealant: 3375066 or equivalent.
Installation of the coolant heater is carried out in the reverse order of removal.
Heater inspection
Clean the coolant heater mounting bore.
Make sure the thread is not damaged.
Clean the heater with a cloth.
Make sure there are no deposits or cracks on the heating element and O-ring.
Check the coolant heater resistance. It must be within the permissible limits.
- Minimum value: 18.2 Ω.
- Maximum value: 21.1 Ω.
Removal and installation of the cooling system fan
- Disconnect the lead from the battery negative terminal.
- Remove the accessory drive belt (article — Replacement of the accessory drive belt).
- Remove the fan shroud.
- Unscrew the 4 fan mounting bolts, remove the fan and the spacer.
Caution! Do not hold the fan by its blades.
Tightening torques:
- M6 — 10 N·m;
- M10 — 43 N·m;
- M12 — 77 N·m.
- Remove the fan pulley.
Fig. 23. Removal of the fan. - Unscrew the four fan hub mounting bolts and remove the fan hub. Tightening torque: 33 N·m.
Fig. 24. Removal of the fan hub.
Installation of the cooling system fan is carried out in the reverse order of removal.
Inspection
Clean the pulley, spacer and fan hub with solvent and dry them with compressed air.
Make sure the fan pulley has no damage or cracks.
Make sure the fan hub and hub chamfer are not damaged and check the fan hub for signs of seal leakage.
Rotate the fan hub and make sure it turns freely and silently.
Check the fan hub bearing:
- check the bearing for wear;
- check the radial and axial play of the bearing. Replace the fan hub if the axial play exceeds the maximum value.
Maximum axial play of the fan hub: 0.15 mm.
Make sure the cooling system fan has no damage, loose bolts, bent or poorly secured blades.
If necessary, replace the fan. When replacing the fan, use a part with the same catalogue number.
Caution! Do not straighten a bent fan blade; replace the cooling system fan.
Make sure the fan shroud is not damaged.
Check the gap between the fan shroud and the fan; it must be within the permissible limits.
Permissible gap limits: 5.08–10.16 cm.
Radiator
Cleaning the radiator
Blow the radiator with compressed air to remove dirt from its core. Air pressure: 552 kPa.
Note: keep the hose nozzle at least 15 cm away from the radiator core to avoid damaging the radiator.
Radiator and cap inspection
Check all hoses for cracks, cuts and crushing. Replace the hoses if necessary.
Make sure the radiator and radiator gasket are not damaged and do not leak.
Remove the radiator cap.
Caution! With a hot engine, this operation must be carried out with care, as water and steam are under pressure.
Check the radiator cap using a radiator tester.
Note: if traces of fluid and/or foreign deposits remain on the cap, rinse and blow out the cap.
By moving the tester plunger, apply pressure evenly and slowly (1 tester plunger stroke per second) to the steam valve of the radiator cap and make sure the valve opens under air pressure.
The radiator cap must ensure tightness within 14 kPa of the value indicated on the cap.
If the valve opening pressure is below the minimum, replace the radiator cap.
Check the cooling system for leaks.
Fill the system with coolant and connect the tester via a hose to the radiator filler neck, as shown in the figure.
- Warm up the engine.
- Using the tester, create a pressure of 138 kPa in the system and make sure the pressure does not drop.
If the pressure drops, check the hoses, radiator and pump for leaks.
Install the radiator cap.
The above materials cover the diagnostics of the Cummins ISF3.8 engine cooling system: checking the radiator cap, radiator, fan and its drive, thermostat, coolant heater, as well as the removal and installation procedures for the listed components. The material is intended for diagnostics, fault-finding and repair of the cooling system.
