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Replacing Your Water Pump
 
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Pelican Technical Article:

Replacing Your Water Pump

Tom Morr

Time:

4 hours4 hrs

Tab:

$70

Talent:

***

Tools:

8mm socket, E8, E10 Torx driver, flathead screwdriver

Applicable Models:

Mercedes-Benz SLK230 (1998-04)

Parts Required:

New water pump and gasket

Hot Tip:

Keep track of where the bolts go

Performance Gain:

Properly cooled engine

Complementary Modification:

Replace your radiator hoses

Most water pump failures result in coolant pooling beneath the car. Another sign that the pump is going bad is 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 (use a glove and watch for heat). 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.

Replacing the water or coolant pump on R170 is certainly a doable job for a DIY'er but it is not a quick job. If this is one of the first projects you are attempting on your car, give yourself at least four hours to get the job done and don't forget to refill the coolant.

There are several things that will need to come off or out of the car to replace your water pump as well as draining your radiator. Please see our articles on how to flush your cooling system for instructions on draining your radiator. Also, please see our article on removing your fan and shroud for instructions on how to remove the shroud.

This article picks up after you have preformed that work.

Loosen the four nuts on the pulley on the coolant pump before you loosen and remove the Poly-v belt.

You are going to remove the Poly-V belt from the water pump but you do not need to remove it completely from the engine unless you are going to replace it. There is a photo below that shows the routing of the belt.

If you want to replace the belt please see our article on replacing your belts as the belt for the Kompressor will need to come off first to completely remove the main belt. Inspect your belt and replace as needed. With an E10 (reverse Torx socket) and driver locate the tensioner and using the Torx driver turn it counter-clockwise. You can now slip the belt off the tensioner. You can also lock the tensioner into the open position if you need both hands to install the new belt. Turn the tensioner all the way counter-clockwise and insert a retaining pin between the rotating part and the tensioner base. If you do not have a retaining pin you can use a 5mm Allen key.

Use a flathead screwdriver and remove the hose clamps securing the two main hoses. The hose for the heater is easier to undo and remove after you have removed the coolant pump.

Remove the six E8 Torx and two E10 Torx bolts holding the pump to the engine. I like to use an old box and draw an outline of the pump on it. There are several different types and lengths of bolts holding the pump on and this makes it much easier to keep track of what goes where.

Pull the pump off the block; this will give you more room to remove the heater hose.

Inspect the pump area of the block for any deterioration or damage if the pump had a catastrophic failure. Some roughness in the housing is part of the casting process and normal.

Make sure you properly clean the mounting surface before you install your pump.

Remember to replace the gasket whether you are installing a new pump or putting the old one back on.

Installation is the reverse of removal and don't forget to fill up the system with coolant. Also, it is easier to finger tighten the water pump pulley then completely tighten to spec after you have installed the belt. Don't forget to do the final tighten on the pulley bolts.

This photo shows the routing of the main Poly-V belt (yellow area).
Figure 1

This photo shows the routing of the main Poly-V belt (yellow area).

Loosen the four nuts (yellow arrows) on the pulley on the water pump before you loosen and remove the Poly-V belt.
Figure 2

Loosen the four nuts (yellow arrows) on the pulley on the water pump before you loosen and remove the Poly-V belt.

You are going to remove the Poly-V belt from the coolant pump but you do not need to remove it completely from the engine unless you are going to replace it.
Figure 3

You are going to remove the Poly-V belt from the coolant pump but you do not need to remove it completely from the engine unless you are going to replace it. If you want to replace the belt please see our article on replacing your belts as the belt for the Kompressor will need to come off first to completely remove the main belt. Inspect your belt and replace as needed. With an E8 (reverse Torx socket) and driver locate the tensioner and using the Torx driver turn it counter-clockwise (red arrow). You can now slip the belt off the tensioner. You can also lock the tensioner into the open position if you need both hands to install the new belt. Turn the tensioner all the way counter-clockwise and insert a retaining pin between the rotating part and the tensioner base. If you do not have a retaining pin you can use a 5mm Allen key.

Use a flathead screwdriver and remove the hose clamps securing the two main hoses (red arrows).
Figure 4

Use a flathead screwdriver and remove the hose clamps securing the two main hoses (red arrows). The hose for the heater (yellow arrow) is easier to undo and remove after you have removed the water pump.

Remove the six E8 Torx (red arrows) and two E10 Torx (yellow arrows) bolts holding the pump to the engine.
Figure 5

Remove the six E8 Torx (red arrows) and two E10 Torx (yellow arrows) bolts holding the pump to the engine. I like to use an old box and draw an outline of the pump on it. There are several different types and lengths of bolts holding the pump on and this makes it much easier to keep track of what goes where.

I like to use an old box and draw an outline of the pump on it.
Figure 6

I like to use an old box and draw an outline of the pump on it. There are several different types and lengths of bolts holding the pump on and this makes it much easier to keep track of what goes where.

Here you can see how you would not want to mix up the bolts due to the different lengths.
Figure 7

Here you can see how you would not want to mix up the bolts due to the different lengths.

Pull the pump off the block (yellow arrow); this will give you more room to remove the heater hose (red arrow).
Figure 8

Pull the pump off the block (yellow arrow); this will give you more room to remove the heater hose (red arrow).

Inspect the pump area of the block for any deterioration or damage if the pump had a catastrophic failure.
Figure 9

Inspect the pump area of the block for any deterioration or damage if the pump had a catastrophic failure. Some roughness in the housing is part of the casting process and normal. Make sure you properly clean the mounting surface before you install your new pump.

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Comments and Suggestions:
khalil Comments: hello I am khalil i have slk 230 kompressor - 2000 - my cooling system is leaking from the thin hose of water vapor attached on the right of the coolant expansion tank,the temperature went higher than 90degrees and when i stop the car the water leaks out from that thin hose that it is should be open to the ground direction for evaporation.thats happen once the engine go high.but there is no other signs of leaking. please can you confirm to me if this problem is from the water pump or coolant flusher or something else that I should do. thank you
October 22, 2015
  Followup from the Pelican Staff: If the engine is overheating, coolant may be expelled. I would check the thermostat and water pump. - Nick at Pelican Parts  

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