Servo pump rebuild

I did notice that the servo pump is pretty dirty and I suspected that the shaft seal is no longer what it should be. So, time to disassemble! There are a lot of toughts and believes about servo's out there, and I think it's time to demystify the poor little bastards.

First of all: Yes, they are units possible to service!

Secondly: It's just a matter of having patience and a clean desk.

Third: It's way easier to disassemble a pump than for example a turbo.

It's really important that the pump is clean before you split it. The smallest sand or dirt can destroy it or make it leaking before you even put it back in the vehicle. In the past I've been using diesel, oil cleaning spray and blah blah blah, but guess what - the hand cleaning soap I have in the workshop is the best dirt killer ever! One pile of the cream and a brush, swipe the part over and rinse. It's clean in a couple of minutes.

The pump is a rotor with a bunch of square shaped loose metal pieces that are pushed out against the elliptic housing (acting like sliding doors), the volume between the clips decreases when the shaft is rotating and the liquid is pressurized and pushed into the oil channel. The flow and the pressure capacity is a combination of the housing itself and the power put into the shaft.

The entire assembly is held together with a single clip. Remove it and you can pull out the shaft. The rotor is usually stuck though because of the oil film on the backside. After the shaft is removed you can push the impeller sideways.

The shaft is surrounded by the pressurized oil and doesn't have a needle bearing or similar. If the shaft sealing is worn out, it will leek immediately as the oil is filling up the housing with pressure all the way up to the sealing.

Now, what I found on my pump is that there's noticeable wear on the shaft. I have to find a new sealing that has a slightly smaller diameter, the sealing itself is pretty odd sized so lets see if I can find a replacement. 

To be continued...