Hydraulic system problems ('85 5000 turbo)

[Huw Powell]

> Thanks for the responses. The pump was a rebuilt one from ebay. 
> It's definitely in better shape than the original.

> So in normal operation, should the fluid level change that much?

Again, saying this not as an expert on that system, but, no, it
shouldn't.  If anything, it might rise slightly as the fluid heats up.
Basically it's a sealed system, so the rach, pump, 1/2 the bomb, and the
hoses, should all be full of fluid only, the reservoir is the only place
there should be air.

> If not, it does sound like air in the system. Air can be compressed, 
> making the fluid go down when pressurized.

Yes, exactly.

> I used the Bentley procedure for bleeding the system: front wheels
> off the ground and turning lock-lock, as Huw mentioned, but it
> didn't seem to do too much.

Interesting, perhaps it needs to be done for longer?  Or preceded by
some "open system" (ie, undo a connection or two) topping up?

> The highest point in the system is the reservoir, servo or the pump 
> itself. Do you think it would be safe to crack open the banjo bolts 
> while running the engine to see if air is stuck there? Thanks again.

I wouldn't want to say yes or no to that, but I don't see why opening
them with it *not* running would hurt - although you might want to use 
new crush washers when retightening.

If you feel the need to run the pump while doing this, you can always 
try spinning it by hand just to move things around.

It would be nice to see the connections at high points overflowing with 
fluid on both sides while reassembling, wouldn't it?

> > The power assist does seem to randomly change.
> 
> > Also, I noticed that the fluid level in the reservoir changes a 
> lot.
> 
> Without being an expert on this particular system, I would have to 
> say my first suspect here is a lot of air still in the system. It 
> probably moves around, and ends up cavitating the pump while its 
> running, killing, or at least randomizing, your pressure and assist.
> 
> I do believe I have read here that bleeding the system is a complex 
> process (but that might have been the cooling system!).
> 
> I don't know if you need to elevate one end of the car at all, 
> but I'm sure you have to turn the steering (with system running) 
> from lock to lock several times.
> 
> Looking at it, you might be able to see where the high points, etc., 
> are and determine the best way to make sure it is air-free.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/