odd problem with power steering

[JonathanT]

I've got a '99 450 with PAS which is behaving oddly/inconsistently at the moment. For the last few outings, it feels like there is little/no power assist for large scale movements, and some assist for finer inputs. Basically, the steering is really heavy. The PAS is clearly doing something, because I can turn the steering wheel when the car is stationary (though it's rather heavy).

Last night, the PAS seemed to be working exactly as it should be through all ranges of input. This morning, it was back to the odd behaviour.

There's a slight weep from what looks like around the steering rack area, but I can't tell from where exactly. I'm not losing a noticeable amount of PAS fluid.

Any ideas?

[SSPPGG]

you may have gaiters full of steering fluid, check those

[JonathanT]

looking from above, there's no evidence of ballooning of the gaitors, nor am I losing a noticeable amount of fluid in the header tank.

[SSPPGG]

in that case, pump flow is most likely to be compromised . ive not had one apart, so dont know if it is rebuildable,

[peaktorque]

Try draining the old fluid out and refilling with new.

More than likely there is plenty of crap that has accumulated in there over time.

[JonathanT]

sounds plausible and a good idea.

[potato muncher]

I was having a problem with mine, it turned out to be a hose from the fluid tank to the rack had perished and kinked.
New hose - sorted.

[JonathanT]

so, I've noticed two things now - the additional "heaviness" reduces with time/use/temperature. Yesterday when it was really cold, it was almost impossible to turn, but this morning which was warmer, it was not so heavy.
Also, I get a little region of "normal" steering around the last bit of steering that I've done. A little hard to describe sensibly.

I'm popping into the garage today, fingers crossed it's something simple/cheap!