Mercedes-Benz Water Pump Replacement

Plan on 8 to 12 quarts of Mercedes coolant, because the system has to come out and go back in properly rather than be topped up. This covers the M112, M113, M272 and M273 V6 and V8 gasoline engines from roughly 1998 to 2013. A water pump that is only weeping now usually announces itself first as a noise from the front of the engine, which is worth catching before it turns into an overheat.

How to Replace Mercedes-Benz Water Pump

Symptoms

• Coolant Leak
• Engine Overheating
• No heat from the vents
• The temperature gauge goes too high in traffic.
• Squeaking Noise
• Low coolant light on
• Bearing Noise
• Play on the water pump pulley
• Whining noise at low and high engine speed
• A leak developed near the lower radiator hose and engine block

Water Pump Noise

The easiest way to check for a bad Mercedes water pump bearing is to use a mechanic’s stethoscope and check for noise near the water pulley.

One way to check if your water pump is failing is to remove the serpentine belt, check the water pump for play, and inspect for coolant leaks. You can start the engine for up to one minute to determine if the engine noise is gone without the water pump running.

Do not continue to operate your car if the water pump fails. If you continue to drive your Mercedes-Benz, you risk causing severe damage to your engine, including blowing the head gasket, cracking the cylinder head, or seizing the engine. All these are costly repairs and, in some cases, may require the engine to be replaced entirely. If your Mercedes water pump fails, it is better to get the car towed than to risk causing additional engine damage.

Common Causes

The primary purpose of a water pump on a Mercedes-Benz is to circulate the coolant in the cooling system of the engine. The most common symptoms of a failed Mercedes-Benz water pump are engine overheating or a small coolant leak.

Mercedes-Benz water pumps suffer from two main issues.

1. Water pump bearings
2. Water pump seals fail / leak

• When the seal fails, it will cause the coolant to leak. If the bearing fails, it will cause abnormal engine noise.

What you will need

• Mercedes Water Pump + Gasket
• Mercedes Engine Coolant
  • You need between 8 and 12 qt.
• Female Torx Socket Set
  • For M272 and M273 engines
• Torx Bit Set for M112 and M113 engines
• Mechanic Toolset Metric

Procedure

Removing the radiator cooling fan is recommended to have more room to work. The fan is straightforward to remove. Disconnect the wire harness, remove the clips or bolts that secure the fan to the radiator, and pull the cooling fan shroud up.

1. Park the Mercedes-Benz in a work area and allow the engine to cool down.
2. Disconnect the battery or batteries if your Mercedes has two.
3. Next, drain the coolant using the drain plug at the bottom of the radiator.
4. Remove the serpentine belt. Use a 17mm socket and breaker bar to remove the drive belt. Next, you must move the tensioner up and use a 5mm Allen wrench to lock the tensioner in the pre-loaded position.
5. We are ready to remove the bolts from the water pump housing. Inspect all the bolts. For example, in some engines, such as M273, you must remove the idler pulley to remove one of the bolts behind it. In older cars, you may need to remove the bolt that secures the water pump to the alternator, for example.
6. Disconnect the radiator hose from the water pump housing. Newer MB engines have a C clip that needs to be moved slightly to pull out the hose. Use a flathead screwdriver to push the C clip to the unlock position.
7. Next, remove the water pump from the engine block. Note that you will get some coolant leaking from the pump even if you drain the system.
8. Clean the perimeter where the water will be installed. If you skip this step, you will have a coolant leak.
9. Install the new water pump and gasket.
10. Torque all the bolts to specification.
11. Install the serpentine belt and all other parts that you removed.
12. Add engine coolant mixed 50/50.
13. Start the engine and check it for leaks.

Torque Specifications

You must verify Mercedes water pump torque specifications by calling your dealer. Torque values vary between engines. The values below are for the M112 and M113 engines.

Alternator bolt	40 Nm
M6 Bolts (not pre-tapped)	15 Nm
M6 Bolts (pre-taped)	10Nm
M8 (Not pre-tapped)	35 Nm
M8 (pre-taped)	25Nm
Idler Pulley	10 Nm

Notes

• If your Mercedes-Benz has a viscous fan (pre-2000 models) and clutches, you will need the Mercedes Fan Clutch Tool to counter-hold the pulley and remove the fan.
• Consider replacing the belt tensioner, serpentine belt, and idler pulley if your Mercedes-Benz has high mileage and has not been replaced.

Safety

• Work only on a cold engine; the cooling system is under pressure when hot.
• Catch and dispose of old coolant properly; it is toxic to people and pets.
• Disconnect the battery before removing the fan or any electrical connectors near the pump.

After the Repair: Bleed the Cooling System

Air trapped in the system causes overheating and a cold heater. Fill slowly with the coolant Mercedes specifies for your car, run the engine with the heater on full, and keep topping up as the level drops. Many Mercedes models also have a bleed procedure using the auxiliary coolant pump, run from the climate control or with a scan tool; check the procedure for your model.

Frequently Asked Questions

How do I know my Mercedes water pump is failing?

Coolant drips or crusty residue near the pump, a whining or grinding noise from the front of the engine, a wobbling pulley, or the temperature rising. Some newer models use an electric pump that sets a fault code instead.

Should I replace the thermostat at the same time?

On higher mileage cars it is a good idea, since the system is already drained and the thermostat is a common failure on many Mercedes engines.

Can I drive with a leaking water pump?

Only a short distance while watching the temperature gauge. If the engine overheats, stop right away; overheating can damage the head gasket.

Check these troubleshooting and repair guides for more help on your Mercedes-Benz.

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