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.

I'm about to do a flush of my cooling system and came across this post. This guy should win the Pulitzer prize for literature. Nice of him to go to the trouble.

BTW, I can't find the drain plug for the block. Any hints?

I went ahead and called the local dealer. They were more than nice. Said pulling the drain plug can be a job trying to reinstall since it is a little difficult to access. Advised since I am going to change the t-stat and flush to do the following:

Drain the radiator and remove the stat.

Replace the housing without replacing the stat.

Detach the heater hose coming off the rear drivers side of the engine and flush from there.

Also said I could go back the other way and flush the heater core.

I am scared. Any comments?

I used this set of instructions to replace the water pump on my 1993 300E last weekend. Wanted to add one comment/correction for any future users.

Step 8 says to remove the four hex bolts on the front of the power steering pump, below the reservoir. Don't do it! These hold the nose of the pump to the body of the pump, when you remove them the nose comes off and all your power steering fluid dumps onto the floor of the garage! Don't ask how I know this.

On my car, the PS pump is mounted via four bolts. Two of these are shared with the tensioner, and two are unique to the PS pump. After removing the tensioner assembly, remove the two PS bolts *from behind the PS pump*. The pump may then be moved to the right for better access to the water pump.

Other than that one minor quibble, everything was spot on. Took me about 4 hours of labor to do the whole job. Not a bad way to save six hundred bucks.

- JimY

Just finished this job and thought I would post some comments based on my experience... My notes are in brackets below the original poster's instructions ...


Some final notes .. pay close attention to the path of the serpentine belt .. there is a diagram here: http://www.peachparts.com/shopforum/attachments/tech-help/12017-1993-300se-belt-tensioner-adjustment-running-diagrams-m104.jpg
... it is easy to mess this up and as a result never get tension on the belt .. the lower right bolt on the Y bracket is a long bolt and a nut so you must have a socket for each end and it is easy to get the back socket on the PS bolt rather than on the nut since you can't see them at all ... as a matter of fact most of this job is done 'in the blind' with many things you cannot see.

and to rant in closing .. I have owned new MB's since the early 70's .. I bought them becaused they were durable, well engineered and held their value well .. this car is my wife's and I have an '03 E model as well .. I can no longer say they are well engineered .. no wonder the shop hours on this job are 5!!! .. there appears to be little thought to after the sale service or to durablility (the '03 has already had more than it's share of problems in very few miles) .. so as much as I would like it to be otherwise I see no reason to continue with MB .. the litany of problems with the '94 is endless and I will dump it real soon ... apologies for the rant ..

is this replacement procedure also applicable for 1990 300CE with engine M104.980? Thanks!

__________________
1996 E320 since 1/16/08, 171K miles as of Feb 2011

---------------------------------------------------------
1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE

Looks the same to me.







Have a great day

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Will this procedure work on a W210 with the M104 engine?

__________________
2010 W212 E350 Sport
1996 W210 E320 (220K miles)

It should be the same.

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Thanks for the great advice on replacing my coolant pump. I appreciate everyone"s comments. The job went smoothly and the car is running fantastic. That car sat for 10 months in Phoenix until I was able to work on it. It started on the first try. Amazing luck or what. I am now in the process of changing the oil, spark plugs, fuel filter, and researching how to fix the AC. My daughter drives the car and was away at college since it first began spewing coolant out the weep hole. It has 150.000 on it and still looks and drives as well as my new cars. I'm sure something will need repair soon, but what a car when it's running. My next purchase is going to be a 1991 420 SEL that has been taken care of like it should have been. Thanks for the help!

On the 104 engine, the use of Snap On number FLX13 will help alot. It is a flex, universal joint with a 1/4" shaft that will get at the water pump bolts with not nearly as much accessory dismantling. I think I paid less than $30 for mine, but that was probably 10 or 12 years ago now. Even if it were $50, I would pay the money to keep from having to do so much field stripping.

The thin shaft on the tool will make you think you are going to twist it in half before the bolt comes loose, but just keep torquing on it. It won't break.

Hope this helps,

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

On a '93 104.942, was able to change out coolant pump without moving the PS pump. Delicate maneuver getting the old out and the new in, but do-able.

Green coolant is a curse. Had a green blob accumulated in the inlet. Stopped the radiator up. Flushed system with citric, refilled with G-05. PO relied on Jiffy Lube for maintenance.

I will also say that this series (104.9XX) is a bit under-cooled IMHO, judging by the size of the radiator. It is a delicate balance, and requires regular maintenance to keep the system operating consistently. UPDATE - The thermostat must be re-installed with the small hole/ball valve at the highest position in the recess housing. This prevents air-lock. Otherwise vacuum will be present via thermal expansion/contraction and the engine may overheat.

__________________
327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

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