Coolant Pump Replace (M276)

Brand: Mercedes-Benz

Model: R350

Chassis: W251

​Engine: M276 DE35

Transmission: 722.9

Project: Repair

​Labor: 3 hours

Water Pump Location
Water Pump Location


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Water Pump
Water Pump


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Parts relations
Parts relations


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Water Pump Location
Water Pump Location


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The vehicle's engine water pump is responsible for keeping coolant flowing through the engine. As water pumps get old the internal bearing can go bad causing noise and a coolant leak. A good indicator that your water pump is failing is if you see coolant leaking through the water pump "weep hole".

Engine Water Pump Failure Symptoms

  • Coolant leak through weep hole

  • Play at water pump pulley shaft indicating a bad bearing

  • Squeaking noise coming from the pump at idle

  • Overheating conditions

  • Low coolant light on instrument cluster indicating a cooling system leak


Step 1  Open The Engine Hood


1.1 Pull lever (1) in the left side of the footwell to unlock the engine hood (2) Engine hood jumps open; lift engine hood slightly if necessary

1.2 Raise handle (3) and open engine hood. Windshield wiper arms must not be folded forward;​

1.3 Press the red release button (4) on the gas-operated strut and position the engine hood vertically.

Step 2 Lift Vehicle


2.1 Jack front vehicle at front central jack point;

2.2 Support vehicle at front side jack points with jack stands;

2.3 Jack rear vehicle at rear central jack point, if w/o rear central jack point, jack at the bottom of differential sell which  fixed at subframe carrier directly;

2.4 Support vehicle at rear side jack points with jack stands.

Step 3 Remove bottom engine compartment paneling


3.1 Remove bolts (4) (8 bolts).​

3.2 Remove rear engine compartment paneling (2) Do not lose washers(5) When installing ensure the washer(5) is seated correctly

3.3 Remove bolt (3) (6 bolts).​

3.4 Remove front engine compartment paneling (1)

Step 4 Drain Coolant from Radiator


4.1 Unscrew cap for coolant expansion reservoir (1) Unscrew cap slowly and relieve excess pressure;​

4.2 Slide collector siphon hose onto fitting (6) at the radiator, The fitting (6) is located at the bottom left of the radiator. 

4.3 Loosen siphon hose (5) at the radiator and drain the coolant. Observe regulations for disposal of coolant.

Step 5 Disconnect battery ground line

Disconnect-connect battery ground line-1


5.1 Move the right front seat completely to the rear;​

5.2 Switch off all electrical consumers to prevent damage;

5.3 Switch off ignition and remove; On vehicles with Keyless Go, Press the start/stop button repeatedly to switch off. Keep the transmitter key away from the vehicle at least 2 m;

5.4 Using a suitable tool moves into the opening of the rail cover (1) (arrow A) and unclip rail cover (1) and move forward (arrow B);

5.5 Lift up the floor covering (2) upwards (arrow C);

5.6 Remove nut (5) to battery negative pole circuit, detach ground line (6) of battery (G1) Ensure that no jumper start device is connected to the vehicle. 6Nm (53 lb-in) for installation.

Step 6 Drain Coolant from Coolant Pump


6.1 Loosen drain screw (7) on the coolant pump (8) until it can be turned by hand, 6Nm (80lb-in) +90° for installation;​

6.2 Push drain hose (9) onto the drain screw (7);​

6.3 Unfasten drain screw (7) further by hand and drain off coolant.

Step 7 Remove Belt