BJ73 1985 Power steering pump rebuild (1 Viewer)

Sep 11, 2020
Leverkusen , Germany
Now for hydraulic oil change and bleeding...
I constructed some aids to limit the mess..

You need to disconnect the return line and block the respective reservoir outlet. I used some 8mm PVC tube that I heated and molded on one end.
The return pipe comes from the bottom, so this copper angulated tubing comes handy. I actually made that for oil filling on axels and transfer case...

The power steering system takes mineral DEXON II fluid.

Regarding the fluid change, my 1st insight was: 1.5l of fluit at hand is not enough.
The system takes ~800 ml for a complete exchange. The reservoir holds about 300ml, so in theory about 3 turns are required.
The issue with having had the pump out is that you need to remove the air from the system. I discarded the used oil (actually only about 0.5I from the steering box and return line was left), which came out straight. The return line will spit out lots of foamy oil then.
I eventually endet up with 2l of new but foamy oil and air in the system, still.
The oil could be poured in again, but it takes hours for the foam bubbles to surface and the oil to clear. So either take your time or have about 3l of oil ready.

For the exchange/ filling procedure:
The engine needs to crank or run in order for the pump to work.
The manual says: "When return line starts to discharge fluid, stop engine IMMEDIATELY'.
This is absolutely essential! The pump suckles out the reservoir in less than 5sec!
Although stopping immediately at beginning of discharge, you will end up with almost the filling of the reservoir being discharged in total.
If you run the engine any longer, your reservoir is empty in no time and air is sucked in again. That sucks.
Forget about turning the wheel lock to lock at this stage. No time at all. For some lame engines even cranking may be enough...
It took me 6 reservoir fillings to get to oil with some bubbles, but not milky or foamy. That makes almost 2l of foamy oil discharged.
You can reconnect the return hose to the reservoir then. Make sure the return hose is full when reconnecting!

Bleeding the system is easy, as it is essentially self bleeding.
Top up the reservoir, start engine and now turn steering lock to lock several times.
Check the reservoir for level and foam. On excess foam you either need to wait for the foam to settle, or take it out using a syringe and replace with fresh oil.
But if oil was almost clear when reconnecting the return line, foam shouldn't appear any more.
Repeat procedure about 5 times.
Check reservoir level often on the first miles.
DONE :bounce::beer:

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