When you open up your engine you will note the three reservoir tanks on the left side of the engine. SLS, Coolant expansion, and the Windshield washer reservoir tank. After 20 years on most cars these items are severely discolored and dirty. Unless you have a low mileage garage collectable E500E and want to maintain original tank patina, you probably want to clean up your engine bay by replacing this reservoir trinity. This HOW-TO covers the Windshield Washer reservoir. There are other great threads and HOW-TOs on the other two.
Parts to order ahead of time:
- my effort focused on the reservoir, washer pumps, caps and grommets o-rings
- Here is a snapshot from EPC that drove my selection of parts (I used Parts.com & Pelican Parts to order what parts.com didn't have)
Washer Reservoir Removal:
- first siphon out all remaining washer fluid in the reservoir
- it is also helpful to remove the air intake hose and the plastic cover behind the headlight assembly to increase your working area
Then you can work on the topside of the reservoir and:
- loosen washer heater hose clamps and remove rubber hoses from heater coil tubes
- disconnect washer level sensor
- unscrew the large white reservoir retention nut
- next I disconnected the electrical connector on both washer pumps
- then I removed both pump motors by lifting up & out
- you don't have to disconnect the washer pumps from their hoses at this time
Now the reservoir is ready to be lifted up and out of the car. Set that aside as now it is time to disconnect the washer pumps from their hoses.
The hoses are secured by two small spring loaded pinch clamps. I used needle nose plier to pinch open and slide it down the hose.
You are now ready to rebuild your new reservoir on your workbench but before doing that I was warned that the new reservoir tank is NOT an exact match of the original reservoir. The problem is there is a large boss at the base of lower reservoir alignment plug. (See picture below and how I modified it). Some have advised to modify the metal bracket on the car side by cutting it and lowering it a bit. This to me is nuts. Do not cut into your car. The tank is a glorified milk jug and with carefully use of a MAP torch I was able to heat up the boss and push it into the tank a bit and not distort any other portion of the tank. The tank is cheap so you can screw this up and order another. I didn't screw it up and never compromised the integrity of the tank to hold water. My reservoir sits perfectly in my car after this mod. In fact, I did a test fit while the boss was still a bit hot and was able to distort the tank to exact position required. Then I poured cold water into the tank to set the plastic in its new position. No one can see the distorted ugliness of the tank after it is installed.
Now you are ready to rebuild your tank.
- remove screw on cap & cover and remove heater tube assembly
- the old heater tube o-rings will probably disintegrate in your hands and then its easy to remove the heater tube assembly from the cap.
- remove the washer level sender
First step is to rebuild the new cap parts with the new heater tube o-rings (A little Dow 111 lube makes o-ring and grommet installs easy)
- a little tip I found out later, the heater tube o-rings are conical on the inside portion, I had to cut this down a little bit to get the o-rings to sit properly after installation. Otherwise they kept pushing out with the cover cap screwed on.
- another tip, I found it impossible to install the little strap holding the washer lid onto the screw off lid. A little exacto knife and some trimming of the plug part on the screw cap helped it go into the hole of the strap. Just take your time and don't force anything.
Prior to putting the tank back in, installed the new pump motors and clamps, put the motor grommets into the tank first, and then install the motors and connectors.
- a note on connecting the washer hoses to the motors. These tubes were pretty brittle on the ends. On headlight washer hose I clipped off the very end to make a fresh connection with the motor for a better seal.
Same thing for the washer level sender, install the o-ring first and then, install the sender.
Finally install the new rebuild lid with heater hose back into the tank and connect the hoses back to the heater tube.
And finally on my car, I have achieved the holy trinity of three clean tanks! From now on I will only use Mercedes washer fluid in my car. need to go to dealer to pick some up.
Parts to order ahead of time:
- my effort focused on the reservoir, washer pumps, caps and grommets o-rings
(I did not dive into rebuilding the thermostat in the washer heater tube assembly)
(I did not change the washer level sensor but I did change the rubber grommet for the sensor)
- on the advice of other I did invest in two new washer pump motors as mine looked original and was advised it is common leak point with age(I did not change the washer level sensor but I did change the rubber grommet for the sensor)
- Here is a snapshot from EPC that drove my selection of parts (I used Parts.com & Pelican Parts to order what parts.com didn't have)
Washer Reservoir Removal:
- first siphon out all remaining washer fluid in the reservoir
- it is also helpful to remove the air intake hose and the plastic cover behind the headlight assembly to increase your working area
Then you can work on the topside of the reservoir and:
- loosen washer heater hose clamps and remove rubber hoses from heater coil tubes
- disconnect washer level sensor
- unscrew the large white reservoir retention nut
- next I disconnected the electrical connector on both washer pumps
- then I removed both pump motors by lifting up & out
- you don't have to disconnect the washer pumps from their hoses at this time
Now the reservoir is ready to be lifted up and out of the car. Set that aside as now it is time to disconnect the washer pumps from their hoses.
The hoses are secured by two small spring loaded pinch clamps. I used needle nose plier to pinch open and slide it down the hose.
You are now ready to rebuild your new reservoir on your workbench but before doing that I was warned that the new reservoir tank is NOT an exact match of the original reservoir. The problem is there is a large boss at the base of lower reservoir alignment plug. (See picture below and how I modified it). Some have advised to modify the metal bracket on the car side by cutting it and lowering it a bit. This to me is nuts. Do not cut into your car. The tank is a glorified milk jug and with carefully use of a MAP torch I was able to heat up the boss and push it into the tank a bit and not distort any other portion of the tank. The tank is cheap so you can screw this up and order another. I didn't screw it up and never compromised the integrity of the tank to hold water. My reservoir sits perfectly in my car after this mod. In fact, I did a test fit while the boss was still a bit hot and was able to distort the tank to exact position required. Then I poured cold water into the tank to set the plastic in its new position. No one can see the distorted ugliness of the tank after it is installed.
Now you are ready to rebuild your tank.
- remove screw on cap & cover and remove heater tube assembly
- the old heater tube o-rings will probably disintegrate in your hands and then its easy to remove the heater tube assembly from the cap.
- remove the washer level sender
First step is to rebuild the new cap parts with the new heater tube o-rings (A little Dow 111 lube makes o-ring and grommet installs easy)
- a little tip I found out later, the heater tube o-rings are conical on the inside portion, I had to cut this down a little bit to get the o-rings to sit properly after installation. Otherwise they kept pushing out with the cover cap screwed on.
- another tip, I found it impossible to install the little strap holding the washer lid onto the screw off lid. A little exacto knife and some trimming of the plug part on the screw cap helped it go into the hole of the strap. Just take your time and don't force anything.
Prior to putting the tank back in, installed the new pump motors and clamps, put the motor grommets into the tank first, and then install the motors and connectors.
- a note on connecting the washer hoses to the motors. These tubes were pretty brittle on the ends. On headlight washer hose I clipped off the very end to make a fresh connection with the motor for a better seal.
Same thing for the washer level sender, install the o-ring first and then, install the sender.
Finally install the new rebuild lid with heater hose back into the tank and connect the hoses back to the heater tube.
And finally on my car, I have achieved the holy trinity of three clean tanks! From now on I will only use Mercedes washer fluid in my car. need to go to dealer to pick some up.
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The washer tube to the passenger headlamp washer is hard and black like a frostbitten toe, I had to cut a fair amount off to find softness. I am just reusing my old reservoir btw; it cleaned up nicely. I will still try the torch on the bottom boss tho on the new one I got.
![[500Eboard] IMG_0702.JPG](/forums/data/attachments/115/115666-9a51890551f60b9d22f6218d5c586667.jpg?hash=mlGJBVH2C5)
