Article by: Gerry at PhoenixMotorsport
Article applies to: BMW e31 models.
I suppose this could be a part 2 for the line filter post done recently but this is how to replace the filter in the bottom of the Pentosin reservoir.
Firstly, remove the cap . . .
to expose the gauze element. Under the top plate, there is a large fiber washer that hardens with age so its wise to have a replacement ready.
Using a 10mm deep socket or similar, undo completely, the nut retaining the gauze filter . . .
and lift away the gauze element, nut and small flat washer.
This will expose the spring, washers and tube that retains the filter in compression.
You can now remove these parts, noting which order they are fitted in as the washers are of different bore sizes.
Then using either a small hand, or a pair of long nose grips, lift out the filter together with its loose top plate and valve.
Here on the view from below, you can see the valve assembly and the lower large diameter rubber seal.
Assuming this was a pre-planned replacement operation, you will now have a shiny new filter ready. Note there are different filters for cars with and without AHK.
You can now insert the valve assembly into the new filter . . . ensuring the two large rubber seals are in position.
The valve assembly has a 3 pronged spring mechanism similar to brake pads to hold it within the filter element . . .
Here you can clearly see the difference between the filter on the left with 40000m on it and the new one . . .
Firstly using a siphon and then a clean rag, I cleaned-out the canister right to the bottom to remove all traces of dirt and a slight layer of sludge.
Before installing the new filter/valve assembly . . .
followed by the tube . . .
washer with LARGE bore . . .
spring . . .
standard M6 flat washer . . .
and the newly washed gauze.
Washed in brake cleaner and dried with an airline.
You can now refit the M6 flat washer and nut and as the nut pulls down, the gauze filter compresses the spring underneath and seats the filter under spring pressure.
The gauze filter will now sit down flush ready to refill the system . . .
with that lovely translucent green CHF11S Pentosin fluid.
So that’s two of the filters in my Pentosin system done, next will be the third in the trunk with the AHK pump.
Oh joy!!!