1991 Mercedes-Benz 190E (W201) Service & Repair Manual

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text 1991 Mercedes-Benz 190E For 1 Copyright © 1998 Mitchell Repair Information Company, LLC Friday, May 06, 2011 10:23PM ARTICLE BEGINNING 1990-93 ENGINE COOLING Mercedes-Benz Specifications & Electric Cooling Fans MODEL IDENTIFICATION NOTE: The following tables identify applicable models covered in this article. MODEL IDENTIFICATION (1990-1993) Year/Model Chassis Number 1990-93 190E 2.3L ................................ 201.028 DESCRIPTION & OPERATION The cooling system consists of a radiator, heat exchanger (heater core), coolant expansion tank, thermostat, belt driven coolant pump and associated coolant hoses. Belt driven coolant pump is always engaged. The cooling fan is engaged and disengaged through a solenoid clutch mounted onto fan pulley. On vehicles equipped with automatic climate control, when solenoid clutch is energized, a 2-stage auxiliary cooling fan is also energized. On all vehicles, solenoid clutch is controlled by a temperature switch located on cylinder head. Thermostat consists of a main valve and a bypass valve. Cooling system is vented through a ball valve located in thermostat valve. Cooling system is vented at the thermostat valve housing through a vent line connected to the coolant expansion tank. COOLANT LEVEL SWITCH Coolant level switch is located in coolant expansion tank. When ignition is turned on, coolant indicator light will dimly light as a bulb test, then goes out when engine is started providing coolant level is sufficient. Coolant level indicator is sealed with an "O" ring and held in position with a circlip. If coolant level is sufficient, a permanent magnet in the float and a permanent magnet in the sensor will hold a contact open. If coolant level is too low, the float moves down and the permanent magnet closes the contact in the coolant level switch. This will brightly light the coolant level indicator on the instrument panel. A permanent ground is present at all times for coolant level indicator. When coolant level switch contacts close this completes the ground circuit causing coolant level indicator light to illuminate. FAN SOLENOID COUPLING

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text (p. 2) 1991 Mercedes-Benz 190EFor 1 Copyright © Cooling fan is engaged when ignition is on with coolant temperature more than 208-216 F (98-102 C). When coolant temperature is less than 208-216 F (98-102 C), cooling fan is disengaged and only continues to rotate because of airflow or inertia. On vehicles equipped with A/C or automatic climate control, the cooling fan (belt driven) and electric auxiliary cooling fan (electric) is energized by a double contact relay which is activated by a triple temperature switch located in cylinder head. See Fig. 1. Fig. 1: Identifying Solenoid Fan Clutch Components Courtesy of Mercedes-Benz of North America. THERMOSTAT Depending on engine temperature, thermostat controls engine cooling through the following valve positions: * When coolant temperature is approximately 189 F (87 C), thermostat main valve closes and bypass valve is open. This stops coolant flow to radiator and allows coolant to circulate in engine block and cylinder head. In this valve position no coolant is routed to radiator, all coolant is recirculated (bypassed) back to engine block and cylinder head. See Fig. 2.

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text (p. 3) 199 * When coolant temperature is approximately 189-216 F (87-102 C), thermostat main valve opens and bypass valve is open. This allows coolant to circulate in engine block, cylinder head and through radiator. In this valve position thermostat allows some coolant to recirculate (bypass) back into engine block and cylinder head, while also allowing some coolant to flow to radiator for cooling. * When coolant temperature is more than 216 F (102 C), thermostat main valve opens and bypass valve is closed. This allows coolant to circulate through engine block, cylinder head and radiator. This type of coolant flow is for optimum engine cooling. In this valve position all coolant is routed through radiator. No coolant is recirculated (bypassed) back into engine block and cylinder head. Fig. 2: Identifying Thermostat Valves Courtesy of Mercedes-Benz of North America. TESTING COOLANT LEVEL SWITCH Coolant Level Indicator On Constantly 1) Disconnect coolant level indicator electrical connector. Coolant level indictor is located at coolant expansion tank. Using a DVOM, check resistance between coolant level indicator terminals. DVOM should indicate infinite resistance. If infinite resistance is present, go to next step. If infinite resistance is not present,

COOLING SYSTEM SPECIFICATIONS - 2.3L Articl replace coolant level switch. 2) Remove instrument cluster. Disconnect 15-pin connector on back of instrument cluster. See Fig. 3. Using a DVOM, check resistance between 15-pin connector terminal No. 12 (Brown/Green wire) and ground. DVOM should indicate infinite resistance. If infinite resistance is present, replace coolant level switch. If infinite resistance is not present, repair short to ground on 15-pin connector terminal No. 12 (Brown/Green wire). Coolant Level Indicator Does Not Light As Bulb Test 1) Remove instrument cluster. Check coolant level indicator bulb. If bulb is okay, go to next step. If bulb is not okay, replace coolant level indicator bulb. 2) With instrument cluster removed, disconnect 15-pin connector on back of instrument cluster. See Fig. 3. Using a DVOM, check voltage between 15-pin connector terminals No. 6 and 9. DVOM should indicate approximately 12 volts. If approximately 12 volts is present, replace coolant level switch. If approximately 12 volts is not present, repair wiring harness as necessary. Fig. 3: Identifying Instrument Cluster Connector Term Courtesy of Mercedes-Benz of North America. Coolant Level Indicator Does Not Light When Coolant Level Is Below Minimum NOTE: For this test procedure to be valid, coolant level must be below minimum. 1) Disconnect coolant level indicator electrical connector. Coolant level indictor is located at coolant expansion tank. Using a DVOM, check resistance between coolant level indicator terminals. DVOM should indicate approximately 5 ohms. If approximately 5 ohms is present, go to next step. If approximately 5 ohms is not present, replace coolant level switch. 2) Connect a DVOM between coolant level switch harness connector Brown wire and battery positive terminal. DVOM should indicate approximately 12 volts. If approximately 12 volts is present, go to next step. If approximately 12 volts is not present, repair wiring harness as necessary. 3) Using a jumper wire, jumper coolant level switch harness connector wires. Turn ignition on. Coolant level indicator should light. If coolant level indicator lights, circuit is okay. If coolant

COOLING SYSTEM SPECIFICATIONS - 2.3L Artic level indicator does not light, repair wiring harness as necessary. COOLANT TEMPERATURE SWITCH With Automatic Climate Control Vehicles equipped with automatic climate control have a 3-pin coolant temperature switch located in cylinder head. See Fig. 1. When coolant temperature reaches 230 F (110 C), coolant temperature switch closes energizing cooling fan solenoid clutch. Verify coolant temperature switch closes when coolant temperature reaches 230 F (110 C). If coolant temperature switch does not complete circuit for cooling fan solenoid clutch, replace coolant temperature switch. When cooling fan solenoid clutch is energized, a 2-stage auxiliary cooling fan is also energized. Without Automatic Climate Control Vehicles not equipped with automatic climate control have a 2-pin coolant temperature switch located in cylinder head. See Fig. 1. When coolant temperature reaches 212 F (100 C), coolant temperature switch closes energizing cooling fan solenoid clutch. Verify coolant temperature switch closes when coolant temperature reaches 212 F (100 C). If coolant temperature switch does not complete circuit for cooling fan solenoid clutch, replace coolant temperature switch. FAN SOLENOID COUPLING NOTE: When cooling fan is disengaged, it may continue to rotate due to airflow or inertia. If cooling fan solenoid is suspected of failing, turn engine off. Disconnect fan solenoid 2-pin connector located behind cooling fan pulley. See Fig. 1. Connect a jumper wire to each terminal of fan solenoid coupling connector (component side). Connect one end of a jumper wire to battery positive terminal. Start engine and idle. Connect other jumper wire to ground. Cooling fan solenoid coupling should energize. If cooling fan solenoid coupling does not energize, replace components as necessary. If cooling fan solenoid engages, verify coolant temperature switch operation. See COOLANT TEMPERATURE SWITCH. Verify wiring harness integrity. Repair as necessary. REMOVAL & INSTALLATION BELT TENSIONER Releasing Belt Tensioner Loosen tensioner pulley bolt 1/4 to 1/2 turn. Turn tensioner adjusting nut until accessory drive belt can be removed. See Fig. 4.

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text (p. 6) 1991 Mercedes-Benz 190EFor 1 Copyright © Fig. 4: Identifying Belt Tensioner Components Courtesy of Mercedes-Benz of North America. Applying Belt Tensioner Install accessory belt onto pulleys. See Figs. 5, 6, and 7. After installing belt onto pulleys, rotate adjusting nut until tip of pointer is over the thick line on adjusting scale. Tighten tensioner pulley bolt to 55 Ft. Lbs. (75 N.m) for 19 mm bolt or 59 Ft. Lbs. (80 N.m) for 17 mm bolt. Fig. 5: Belt Routing Without Power Steering Courtesy of Mercedes-Benz of North America.

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text (p. 7) 1991 Mercedes-Benz 190EFor 1 Copyright © Fig. 6: Belt Routing With Power Steering Courtesy of Mercedes-Benz of North America. Fig. 7: Belt Routing With Power Steering & A/C Courtesy of Mercedes-Benz of North America. WIRING DIAGRAMS

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text (p. 8) 1991 Mercedes-Benz 190EFor 1 Copyright © Fig. 8: Cooling Fan Circuit Wiring Diagram (1990 2.3L) Fig. 9: Cooling Fan Circuit Wiring Diagram (1991-92 2.3L) Fig. 10: Cooling Fan Circuit Wiring Diagram (1993 2.3L)

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text (p. 9) 1991 Mercedes-Benz 190EFor 1 Copyright © Fig. 11: Cooling Fan Circuit Wiring Diagram (1990-91 2.6L) Fig. 12: Cooling Fan Circuit Wiring Diagram (1992 2.6L)

COOLING SYSTEM SPECIFICATIONS - 2.3L Article Text (p. 10) 1991 Mercedes-Benz 190EFor 1 Copyright Fig. 13: Cooling Fan Circuit Wiring Diagram (1993 2.6L) END OF ARTICLE

1991 Mercedes-Benz 190E (W201) Service & Repair Manual

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