In this guide, you will find step-by-step instructions on how to change a Mercedes-Benz water pump. 

The instructions in this guide apply to M112, M113, M272, and M273 engines, found on many models including C, E, S, CLK, ML, GL, SLK, CLS, G, R class, etc.

Symptoms

• Coolant Leak
• Engine Overheating
• No heat from the A/C vents
• Temperature gauge goes to 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
• Leak developing near the lower radiator hose and engine block

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 so that you can have more room to work. The fan is very easy 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 your Mercedes-Benz on 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 move the drive belt off. You will need to move the tensioner up, and use a 5mm Allen wrench to lock the tensioner in the pre-loaded position.
5. Now we are ready to remove the bolts from the water pump housing. Inspect all the bolts. In some engines such as M273, for example, you will need to 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 flat head 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 end up with 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 the engine 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 M112 and M113 engines.

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.

A common symptom that your Mercedes water pump is bad, is the engine overheating or coolant leak at the front of the engine. A water pump symptoms develop over time before the pump completely fails.

One way to check if your water pump is failing is to remove the serpentine belt and 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 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 risk causing additional engine damage.

Tips

• If your Mercedes-Benz has a viscous fan (pre-2000 models) and clutch you will need 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 those items have not been replaced.

FAQ

How do Mercedes-Benz water pumps fail?

The primary purpose of the water pump on your Mercedes-Benz it to circulate the coolant in your engine's cooling system. The most common symptoms of a failed Mercedes-Benz water pump is the 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. Below is a list of possible symptoms caused by a bad Mercedes water pump.