1994
Chassis: E320
Engine: M104.992

Just thought I'd post the way I changed out my water pump. Not that bad of a DIY job if you take your time.





1. Disconnect the ground cable.

REFIT: Reconnect.



2. Drain the coolant.
Open the expansion tank cap. Place a hose on the drain outlet of the radiator
at the bottom left of the unit.(about 3/8” OD vinyl hose will work, might need to
cut a small slit to get it to fit the drain outlet). Open the drain plug slowly and
gently.
Drain the engine block from the bolt which is located on the left bottom side of
the engine near the exhaust pipe. This is not absolutely necessary since most
of the block will drain when you pull the pump off.....although a bit messy.

REFIT: Use a 50/50 mix of Mercedes Anti-freeze (DO NOT use any other
types...unless you want to do this all again next year) and water. Make sure the drains
are closed. Add to the expansion tank. When it shows full, run the engine with the cap
off, with the heat on, until the temp raises to the point the thermostat is set for. Put the
cap on and continue running a few minutes. You will likely need to add more later.



3. Remove Fan Shroud
Unhook the center clasp and turn the narrow circle shroud to unlock, lay it over
the fan.
Remove clips on the shroud, pull up and then remove the circle.
Remove the black plastic cover at the front of the valve housing. (just behind the
fan)

REFIT: Lay the circle shroud over the fan. Reattach the shroud and connect the
circle to it. Replace the black plastic cover at the front of the valve housing.



4. Remove Fan with Visco Clutch
Make a “pulley securing tool” using a 3/16” x 12+” steel rod with a 45 degree
angle, 3/4” from the rod end.
Insert the 3/4” bent end behind the fan pulley, into the pre-cast groove, slowly
turn the fan by hand until it locks in place.
Take a long neck 8mm Allen Key and insert it into the hex bolt on the front of the
fan. Put a 3/4” x 18” pipe over the long part of the Allen key for leverage. USE
CARE NOT TO DAMAGE THE RADIATOR FINS.
Unscrew (normal turn) the hex nut...lean on it if necessary. Make sure the rod
keeps the pulley locked.
Remove the fan.

REFIT: Secure the fan well. You may or may not need to use the tool at the pulley
while reattaching.




5. Remove radiator hoses and thermostat housing.
Remove those which will obviously be in your way. Replace those that are hard
or cracked.

REFIT: Replace thermostat. Re-attach all hoses.


5. Remove the Serpentine Belt
Loosen the 10 mm Allen keyed bolt on the tension pulley by 1-2 full turns. This
is located to the right of the water pump pulley...about 4 o’clock position.
Use a 10mm hex socket for this....also might require some torque to bust loose.
Loosen the 13mm adjusting nut 1/2 turn on top of the tension adjuster. Its a long
bolt with a hollow interior located just to the right of the thermostat housing.
You should now be able to remove the belt. If it shows wear, replace it.

REFIT: Put the belt on the pulleys correctly. Turn the long 13mm tension nut
adjuster until there is 3/8 to 1/2” belt deflection between the long run of the pulleys. Do
not over tighten. Reset the white pointer on the pulley to the solid line at the left on the
indicator. Tighten the 10mm Allen bolt near the water pump pulley.


6. Remove the water pump and power steering pulleys.
These are 13mm hex nuts. Use a second wrench to counter the pulley from
turning while loosening.

REFIT: Bolt the pulleys back in place.



7. Remove the tension adjuster mechanism.
Completely remove the 10mm Allen keyed tension pulley bolt (this is the first
one you loosened in Step 5.)
Remove the “Y” bracket in front of the tension pulley.
Unscrew the hex bolt at the top of the little shock absorber on the tension system.
Remove the entire unit. If it is tough to get out of the space, hold off until you
loosen the power steering pump in the next step.

REFIT: Place the long tension nut through the bracket opening, bolt the shock
absorber in place, refit the Y bracket and put the 10mm Allen bolt back in. Make sure the
white pointer is in the marked area of the housing...don’t set it at this time.



8. Loosen the Power Steering Pump and move it to the right a little.
Unscrew the 4, 13mm hex bolts on the front face of the power steering pump.
They are the ones which make a square under the PS reservoir. One of these bolts
has a nut on the back side.

REFIT: Re-secure the PS pump with the proper bolts. ( you may want to first
re-install the tensioner device before tightening down the PS...allows a bit more room)



9. Remove the Water Pump.
Remove the solid heater pipe from the front of the pump. Leave this solid pipe
attached at the other end.
Use a 6mm Allen key and Allen socket to get to the 4 bolts holding the pump to
the block. They should now be accessible using a ratchet extension and/or
the Allen key levered with a small closed end wrench.

REFIT: Clean off the surface of the engine block. Insert O ring into the pump and
give the O ring a light layer of grease. Insert the weep drain tube to the bottom of the
pump. Mount the pump to the block.
Place the small O ring on the heater pipe (might want to also add some
grease to it and/or gasket gel). Reconnect it to the pump.