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Pelican Technical Article:

Coolant Pump Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$150

Talent:

****

Tools:

Set of sockets T50 Torx, 10mm, 17mm, E10, E12,

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Water pump, hoses, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Car will cool down again

Complementary Modification:

Change serpentine belt, radiator hoses

Your cooling system is critical to extending the life of your engine. While the engine lubrication system is very important, your cooling system keeps the engine running at the correct temperature while you are driving. If the engine is running a little hot from a bad coolant pump not circulating enough coolant, the oil will start to break down from the additional heat and provide less lubrication. This is known as thermal breakdown of the engine oil. The coolant pump is the heart of the cooling system. It pumps cooled coolant through the cylinder jacket and the heads to control engine temperature. The coolant gets circulated through the block, head, heater system, radiator and finally returns to the coolant pump.

When a water pump begins to fail, you'll notice that the car tends to overheat at low engine speed, such as sitting at a stoplight. When you accelerate, the engine temperature will drop. Now, this is not always indicative of a water pump, but a good starting point. You may also want to try squeezing the top radiator hose with the engine warmed up and running. You should feel pressure build up on the back of the hose and surge once it is released. If you feel no pressure, it's a fair bet that the water pump is failing. Sometimes, you can also see a slight drip coming from the water pump housing itself. These weep holes are cast into the pump housing and allow excess coolant to drain out if it has leaked past the various seals in the pump. The bearing can fail creating a grinding noise or creating free-play in the shaft, also resulting in a coolant leak.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

In this article, I'll go over the steps involved with replacing the water pump on Mercedes-Benz W211 models with a 6-cylinder engine. Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening the cooling system.

Drain the cooling system. See our tech article on the cooling system draining and filling.

The water pump on W211 models with a 6-cylinder engine is mounted to the front of the engine (red arrow).
Figure 1

The water pump on W211 models with a 6-cylinder engine is mounted to the front of the engine (red arrow). To access this, begin by removing the engine covers.

Working at the engine cover (red arrow), pull off the two front air duct hoses (green arrows).
Figure 2

Working at the engine cover (red arrow), pull off the two front air duct hoses (green arrows).

To detach the ducts, pull them straight off the engine cover/air filter housing.
Figure 3

To detach the ducts, pull them straight off the engine cover/air filter housing. Then pull the front of the duct out of the radiator support and remove it from the engine. Repeat this step for each duct.

Lift up and remove the front engine cover.
Figure 4

Lift up and remove the front engine cover.

Then, pull the engine cover/air filter housing straight up to remove it.
Figure 5

Then, pull the engine cover/air filter housing straight up to remove it. Four metal clips that grab onto rubber mounts hold on the cover. The front two are shown (red arrows). The rear of the cover has two as well. Once detached, remove the engine cover/air filter housing from the engine.

Before removing the engine drive belt, loosen the four 10mm water pump pulley fasteners (red arrows).
Figure 6

Before removing the engine drive belt, loosen the four 10mm water pump pulley fasteners (red arrows). Do not remove them yet.

Locate the accessory drive belt tensioner (red arrow) on the left side of the engine.
Figure 7

Locate the accessory drive belt tensioner (red arrow) on the left side of the engine.

Using a ratchet with a long handle and a 17mm socket, rotate the drive belt tensioner counterclockwise to release tension and slide the belt off the pulleys (red arrow).
Figure 8

Using a ratchet with a long handle and a 17mm socket, rotate the drive belt tensioner counterclockwise to release tension and slide the belt off the pulleys (red arrow). Remove the engine drive belt. See our tech article on engine drive belt replacing for detailed information.

If the pulley was spinning and you couldn't break the bolts free, hold the pulley still using a flathead screwdriver.
Figure 9

If the pulley was spinning and you couldn't break the bolts free, hold the pulley still using a flathead screwdriver. Then loosen the four 10mm water pump pulley fasteners (red arrow).

Locate the accessory drive belt tensioner and remove the dust cap (green arrow) using a flathead screwdriver.
Figure 10

Locate the accessory drive belt tensioner and remove the dust cap (green arrow) using a flathead screwdriver. Then remove the water pump pulley. If the pulley is stuck, gently lever it off using a flathead screwdriver. If you have to lever it off, be sure it is not bent when reinstalling. Replace if necessary.

Using a T50 Torx socket, remove the idler pulley fastener (red arrow).
Figure 11

Using a T50 Torx socket, remove the idler pulley fastener (red arrow).

Slide the idler pulley out of the water pump with the bolt.
Figure 12

Slide the idler pulley out of the water pump with the bolt.

Working at the bottom of the water pump, loosen both hose clamps.
Figure 13

Working at the bottom of the water pump, loosen both hose clamps. Then remove the coolant hoses (red arrow) from the water pump.

Working at the top of the alternator, remove the E14 bolt (red arrow).
Figure 14

Working at the top of the alternator, remove the E14 bolt (red arrow).

Remove the two E10 solenoid bracket fasteners (red arrows).
Figure 15

Remove the two E10 solenoid bracket fasteners (red arrows). Then move the bracket aside and remove the E12 water pump fastener behind it. Then remove the E12 fastener closest to the alternator (yellow arrow).

There are 13 remaining water pump fasteners, 10 of which are E10 and three are E12.
Figure 16

There are 13 remaining water pump fasteners, 10 of which are E10 and three are E12. Remove them all, using this gasket as a guide. Note the position of each fastener, as they are almost all varying sizes.

Remove the water pump from the engine by pulling it straight off.
Figure 17

Remove the water pump from the engine by pulling it straight off. If the water pump won't budge, you have a fastener remaining. Do not lever on the pump. They always fall right off, when the fasteners are removed, due to the metal gasket. Once off, remove the gasket (green arrow) and clean the sealing surface.

Install the new gasket to the pump.
Figure 18

Install the new gasket to the pump. Slide two E12 bolts (green arrows) through the water pump to hold the gasket (red arrow) in place. Install the pump to the engine. Guiding the fasteners into the housing, be sure that the gasket doesn't slip. Hand tighten the fasteners in a crisscross pattern slowly. Tighten one a few turns, then the next and so on. Install the water pump pulley and tighten the fasteners. Install the engine drive belt and fill and bleed the cooling system. Once complete, check the cooling system for leaks and top up the cooling system. 

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Comments and Suggestions:
abemiami Comments: I have an E320 W211 6 cylinder, but it's a CDI not a V6, very different engine, do you have the technical article for it?
Thanks in advance.
April 18, 2016
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

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