While the Eheim Pro II is one of the most reliable filters in the hobby it is subject to wear and tear just like any other. An area of concern is the primer. Often the primer may become stiff or even stuck completely or the o-ring which which seals the motor/primer may cause slight leakage after years of use. Unfortunately the o-ring is not available from Eheim separately and would require purchase of a new pump head assembly.
I found an easy fix to both problems using o-rings I have sourced from theoringstore.
The sizes you will need are 4.5mm X 92mm for the motor/primer and a 2.5mm X 12mm for the flow control indicator.
This is what I ordered:
N4.50X092 Metric Buna-N 70 O-ring $2.80
2.5mm X 12mm Metric Buna-N 70 O-ring $0.22
The replacement is simple and can be done with basic hand tools. You will need a #1 Phillips screwdriver, a #2 Phillips screwdriver, a small flat blade screwdriver and a standard pliers. You should also have some silicone grease on hand to lube the o-rings and gaskets during installation.
Here's a step by step instruction with photos
1. Remove pump head from your filter and set it on a clean work surface.
2. Remove the Eheim logo cover plate using the small flat blade screwdriver
3. Remove impeller cover and impeller assembly.
4. Turn the pump head over and using pliers to depress the retainer tabs, remove the flow control valve. It may need a little wiggling to get it free. Be gentle and patient.
5. Lift out flow control valve.
6. Turn the pump head over and remove the two Phillips head screws as shown using the #1 Phillips screwdriver.
7. Turn the pump head over and remove the four Phillips head screws as shown using the #1 Phillips screwdriver.
8. Remove the top cover to expose the motor housing, motor, and primer. (NOTE: I have already removed the flow control indicator in this photo)
9. Remove the two Phillips head screws holding the motor cord to the lower housing.
10. You can now lift out the motor/primer assembly and will see the o-ring just under the cover. Be careful to watch the springs so they don't go flying.
This is the flow control indicator. It just pops out when releasing the two tabs.
11. Remove the three Phillips head screws from the motor cover using the #1 Phillips screwdriver.
12. Remove the o-ring from the motor. Clean the motor as best you can being sure to clean out all the gunk (factory grease) from the o-ring land. Thoroughly clean the lower pump housing especially the areas where the o-ring will be contacting. Once clean and dry, install the new o-rings with a light coating of silicone grease. Replace the o-rings on the motor and the flow control indicator.
This is what I use.
Motor o-ring (Note: The factory o-ring is orange. The replacement from theoringstore will be black)
Flow control indicator o-ring.
13. Install flow control indicator by sliding it into place
14. Install motor cover to motor with the three screws. Just snug the screws, do not over tighten them.
14. Install the four primer springs
15. Install motor back into lower pump housing being careful to allow the o-ring to slide in smoothly.
16. Install the motor cord to the lower housing using the retainer and two screws.
17. Install the top cover over the lower housing and install the four small screws at the corners with the pump head upside down. Apply a little pressure to the primer to hold it down against the springs just enough so the top cover and the lower housing meet (a helper is handy). tighten the screws snug, not too tight as it is plastic and you don't want to strip it.
18. Turn the pump head over and install the two larger screws. Again make them snug, not too tight.
19. Install impeller and impeller cover.
20. Install Eheim logo cover plate by snapping it into place
21. Install pump head back on the filter. Connect your water lines. Depress the primer button (it should now move like new again). Let water fill the filter and turn it on. If you did everything correctly you should have years of use left in your Eheim Pro II.
I found an easy fix to both problems using o-rings I have sourced from theoringstore.
The sizes you will need are 4.5mm X 92mm for the motor/primer and a 2.5mm X 12mm for the flow control indicator.
This is what I ordered:
N4.50X092 Metric Buna-N 70 O-ring $2.80
2.5mm X 12mm Metric Buna-N 70 O-ring $0.22
The replacement is simple and can be done with basic hand tools. You will need a #1 Phillips screwdriver, a #2 Phillips screwdriver, a small flat blade screwdriver and a standard pliers. You should also have some silicone grease on hand to lube the o-rings and gaskets during installation.
Here's a step by step instruction with photos
1. Remove pump head from your filter and set it on a clean work surface.
2. Remove the Eheim logo cover plate using the small flat blade screwdriver
3. Remove impeller cover and impeller assembly.
4. Turn the pump head over and using pliers to depress the retainer tabs, remove the flow control valve. It may need a little wiggling to get it free. Be gentle and patient.
5. Lift out flow control valve.
6. Turn the pump head over and remove the two Phillips head screws as shown using the #1 Phillips screwdriver.
7. Turn the pump head over and remove the four Phillips head screws as shown using the #1 Phillips screwdriver.
8. Remove the top cover to expose the motor housing, motor, and primer. (NOTE: I have already removed the flow control indicator in this photo)
9. Remove the two Phillips head screws holding the motor cord to the lower housing.
10. You can now lift out the motor/primer assembly and will see the o-ring just under the cover. Be careful to watch the springs so they don't go flying.
This is the flow control indicator. It just pops out when releasing the two tabs.
11. Remove the three Phillips head screws from the motor cover using the #1 Phillips screwdriver.
12. Remove the o-ring from the motor. Clean the motor as best you can being sure to clean out all the gunk (factory grease) from the o-ring land. Thoroughly clean the lower pump housing especially the areas where the o-ring will be contacting. Once clean and dry, install the new o-rings with a light coating of silicone grease. Replace the o-rings on the motor and the flow control indicator.
This is what I use.
Motor o-ring (Note: The factory o-ring is orange. The replacement from theoringstore will be black)
Flow control indicator o-ring.
13. Install flow control indicator by sliding it into place
14. Install motor cover to motor with the three screws. Just snug the screws, do not over tighten them.
14. Install the four primer springs
15. Install motor back into lower pump housing being careful to allow the o-ring to slide in smoothly.
16. Install the motor cord to the lower housing using the retainer and two screws.
17. Install the top cover over the lower housing and install the four small screws at the corners with the pump head upside down. Apply a little pressure to the primer to hold it down against the springs just enough so the top cover and the lower housing meet (a helper is handy). tighten the screws snug, not too tight as it is plastic and you don't want to strip it.
18. Turn the pump head over and install the two larger screws. Again make them snug, not too tight.
19. Install impeller and impeller cover.
20. Install Eheim logo cover plate by snapping it into place
21. Install pump head back on the filter. Connect your water lines. Depress the primer button (it should now move like new again). Let water fill the filter and turn it on. If you did everything correctly you should have years of use left in your Eheim Pro II.