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Pelican Technical Article:

Coolant Pump Removal

Kerry Jonsson

Time:

4 hours4 hrs

Tab:

$250

Talent:

***

Tools:

10mm, 13mm sockets, 6mm Allen head bit with ratchet and extensions

Applicable Models:

Mercedes-Benz 500SL (1990-93)
Mercedes-Benz SL500 (1994-02)

Parts Required:

Coolant pump, thermostat, thermostat housing, coolant

Hot Tip:

Drain the cooling system from the block to prevent a coolant mess

Performance Gain:

Repair over heating condition from low coolant flow

Complementary Modification:

Flush the cooling system and replace the accessory drive belt

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. Coolant pump failures can be caused by the impeller on the inner part of the water pump to not spin with the outer drive pulley or the bearing failing allowing the pulley and impeller to "wobble" around in the pump housing. As a side note the coolant pump also houses the thermostat. Unlike other cars you cannot remove the thermostat to temporarily improve cooling flow. The Mercedes Benz design requires a thermostat and the car will overheat without one. In this tech article we will go over all the steps to remove the coolant pump.

In order to remove the coolant pump you will need to remove the cooling fan shroud, cooling fan and accessory drive belt. See our tech articles on cooling fan and shroud and accessory drive belt for more detailed instructions on removal.

This picture illustrates the front of the engine compartment.
Figure 1

This picture illustrates the front of the engine compartment. Remove the cooling fan and shroud. See our technical article is on cooling fan and shroud removal for further instructions.

Remove the accessory drive belt.
Figure 2

Remove the accessory drive belt. See our tech article on accessory drive belt removal for further instructions.

Loosen the clamp on the upper radiator hose and remove the hose from the neck.
Figure 3

Loosen the clamp on the upper radiator hose and remove the hose from the neck.

Remove the water pump pulley by removing the four 10 mm fasteners (green arrows).
Figure 4

Remove the water pump pulley by removing the four 10 mm fasteners (green arrows).

Also remove the idler pulley by removing the four 10 mm fasteners (green arrows).
Figure 5

Also remove the idler pulley by removing the four 10 mm fasteners (green arrows).

You do not need to remove the entire alternator.
Figure 6

You do not need to remove the entire alternator. You only need to remove the top mounting bolt. I suggest you remove the alternator because it gives you more room to work. See our technical article on alternator removal for further instructions.

If the vehicle has cruise control remove the three 10 mm fasteners (green arrows) that hold on the actuator.
Figure 7

If the vehicle has cruise control remove the three 10 mm fasteners (green arrows) that hold on the actuator.

Use a straight blade screwdriver to lever off the cruise control actuator linkage.
Figure 8

Use a straight blade screwdriver to lever off the cruise control actuator linkage. You do not have to unplug the actuator simply move it out of the way.

This picture illustrates the right side of the water pump.
Figure 9

This picture illustrates the right side of the water pump. Loosen the two hose clamps (green arrows) for the thermostat hose and lever out the hose.

Once the hose is removed, remove the two 13 mm fasteners (green arrows) that hold on the top of the coolant pipe.
Figure 10

Once the hose is removed, remove the two 13 mm fasteners (green arrows) that hold on the top of the coolant pipe.

This picture illustrates the bottom of the coolant pipe.
Figure 11

This picture illustrates the bottom of the coolant pipe. Remove the single 13 mm fastener (green arrow) that secures the bottom of the cooling pipe.

Note the coolant pipe is still attached to the air pump.
Figure 12

Note the coolant pipe is still attached to the air pump. Push the cooling pipe ports to the right side of the car until it clears the water pump (green arrow). It will pivot off of the air pump mount.

This picture illustrates the top front of the engine.
Figure 13

This picture illustrates the top front of the engine. Lift the wire plastic sheathing or off of the throttle linkage bracket

Remove the four 5 mm Allen head fasteners (green arrows) that mount the bracket to the cylinder head.
Figure 14

Remove the four 5 mm Allen head fasteners (green arrows) that mount the bracket to the cylinder head. You will need a long swivel 5 mm Allen socket or shortened 5 mm Allen key to loosen the lower bolt (yellow arrow) on the left side cylinder head. If you do not have either you will have to remove the power steering fluid reservoir. See our tech article on power steering fluid reservoir removal.

This picture illustrates the left side of the water pump.
Figure 15

This picture illustrates the left side of the water pump. Start by removing the five 13 mm fasteners (green arrows) if on the left and right side of the water pump.

This picture illustrates the bottom of the water pump.
Figure 16

This picture illustrates the bottom of the water pump. There is one 13 mm fastener (green arrow) that needs to be removed. You can loosen the bolt with a wrench but you will not be able to pull the bolt out all the way because it will hit the crankshaft harmonic balancer.

Remove the 27 mm crankshaft bolt (green arrow).
Figure 17

Remove the 27 mm crankshaft bolt (green arrow). This will allow you to pull off the harmonic balancer and access the one water pump bolt hidden behind it. You will need a special tool to secure the crankshaft pulley in place when tightening and loosening. Click here for MBZ tools.  (A universal pulley holder may work too.)

This picture illustrates the top front of the engine looking downward.
Figure 18

This picture illustrates the top front of the engine looking downward. With a flat head screwdriver loosen the clamp to the water pump hose (green arrow).

Remove the three 5 mm Allen head fasteners (green arrows) that mount the bleeder screw housing.
Figure 19

Remove the three 5 mm Allen head fasteners (green arrows) that mount the bleeder screw housing.

Pull the bleeder screw housing out of the cooling hose and out of the way.
Figure 20

Pull the bleeder screw housing out of the cooling hose and out of the way.

Remove the last 13 mm water pump fastener found behind the bleeder screw housing.
Figure 21

Remove the last 13 mm water pump fastener found behind the bleeder screw housing.

Lift the throttle linkage bracket slightly and you can now fully remove the water pump from the engine.
Figure 22

Lift the throttle linkage bracket slightly and you can now fully remove the water pump from the engine. Clean the gasket surfaces on the timing case cover. You can use silicone or weather strip adhesive to glue the gasket either to the water pump or the timing case cover. Install the water pump and pull off its mounting fasteners. Install a new gasket for the bleed screw housing, tighten down the fasteners and the hose clamp. Position the cooling pipe bracket over the water pump and tighten the final fastener. Install the crankshaft pulley and torque down the crankshaft bolt. Install the throttle linkage bracket and tighten down the fasteners. Fit the water pump pulley and that the idler pulley and tighten down four fasteners. Install the accessory drive belt and radiator hose. Fit the mechanical cooling fan and shroud. Fill the cooling system with proper coolant and check for any visual leaks. Start the engine and follow our tech article on draining refilling and bleeding your cooling system. Verify the engine does not overheat.

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Comments and Suggestions:
Johnny Quest Comments: Thanks Nick. BTW I had not find the tiol to hold the pulley in front of the harmonic balancer the one on ebay are not for 1991 MB 500SL I have a 1999 and in that one will fit, don't have and idea of what it looks like !!!!
November 30, 2016
  Followup from the Pelican Staff: NP. I am having the factory tool info added to article, I can have them add generic pulley holder as well. - Nick at Pelican Parts  
Johnny Quest Comments: Nick I had gone krazy by trying to remove the 27mm bolt at the crankshaft I had tried to the left and right and I coyld hear the piston moving AND JUST FOUD OUT THRU A COMENT THAT YOU NEED A SPECIAL TOOL TO HOLD THE BALANCER AND THAT REQUIERES A 270 LB TORQUE !!! Thanks for not posting a piece of information so vital to the DYS mechanic to be lol..... Now by forcing the crankshaft have I taken damage the timeing on the car or is something that will automatically balence it self ???
Any way will call tomorrow.
November 27, 2016
  Followup from the Pelican Staff: I responded to a person in Jan regarding the special tool. I will be sure the info is added.

As long as you didn't rotate the engine (more than 30°) opposite direction of rotation, timing should b=not be affected. - Nick at Pelican Parts
 
Jack Comments: Hi Nick, where can I get a list of all torque specs regarding the replacement of the coolant pump and all the associated parts.
June 28, 2016
  Followup from the Pelican Staff: 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
 
Paul Comments: Don't you need to use a tool at the engines flywheel to stop the crank from turning when taking off the 27mm bolt and when reinstalling it? You have to torque this bolt about 275 ft. lbs.
January 23, 2016
  Followup from the Pelican Staff: You will need a special tool to secure the crankshaft pulley in place when tightening. I will see if I can have that info added to the article. - Nick at Pelican Parts  

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