E30 Zone

The other day my power steering failed suddenly so I assumed the belt had snapped, but it is there and tensioned OK. The pump spins OK even if I take the belt off and turn it by hand.

The liquid is quite new and at the correct level.

If I turn the wheel from lock to lock with the engine running though, there is absolutely no movement in the fluid reservoir.... which makes me think that either the pump is doing nothing internally, or the rack is totally blocked up and not allowing the pressure to circulate.

Any ideas on how to check what's going on without randomly throwing expensive parts at it?

New one on me, but I don't think the pump is working and the circulation blocked. This would be the same as happens when you turn the steering wheel fully one way or the other on a working system - The pump groans, belt protests, and the engine noticeably works harder.
Based on pure guesswork, I'd expect the problem to be with the valve assemblies in the rack pinion housing, but if you want to check something, then the pump is fairly simple inside. If you open it up, it should be fairly simple to see if anything is broken.

Thanks for the feedback.

I did some preliminary checks yesterday (turning lock to lock with the motor at tick over, then with the motor off) and have concluded that it is not actually a total loss of power to the rack, there is still some assistance, but it is minimal.

I drove the car a bit and searched for evidence of a leak from the high pressure parts of the system but can't find any.

I have no idea how to check a rack, but I do have a spare pump kicking around so I might make sure that it looks OK internally and swap it over and see what happens. The only other thing I can think of is changing the fluid, but I can't really see the benefit of that?

Dirty fluid may be the cause of the problem, but changing it now is unlikely to help.
If you have a spare pump, swapping them over would be a easy way of confirming where the fault is.

Swapped the pump and now I have a working (but leaking ) system.

I might open up the old pump to see what I can see because it's annoying to be unsure if it was the changing of the pump which solved the problem, or the new fluid. But priority now is to stop the leak!

I'm hoping its just a banjo bolt neding tightening, I used new crush washers.

Update and oddness....

Stopping the leaks was easy, new crush washers and replacing the hose clamps solved it completely, so I went on my merry way with PAS again and drove it for about a month.

Then the other day I started the car in the morning and as I went to turn to leave the garage, the steering had gone heavy again... but as I turned the wheel more I felt (more than heard) a "click" and the steering freed up again, but now the steering is even lighter!

Been driving a few days with nice light steering and no issues...

What do you think? The new clean fluid and "better" pump pressure has freed up a sticking valve in the rack? Its the only thing I can think of.

Yes, quite possibly.

Now it does this every day (possibly due to the cold temperature?)

Is there a "thinner" ATF I could use for a while to try to flush the system?

I'd be wary of using anything other than the specified PAS fluid, else you may damage the various seals.

Understood. There are a few "flushing additives" available for PAS systems, but I am always wary of snake oil fixes..

I was wondering if different versions of Dexron may have different viscosities, but as far as I can see only Dexron 6 has a slightly lower viscosity. Probably not worth trying.

Just seen that Brian says NO to Dexron 6 in another thread... so that's a NO then!

Have you opened up the old pump yet?
I am thinking that if there is visible damage then maybe you have "swarf" in your rack?
I dont know if there is a filter of any sort in the PAS system?

Carmo13 wrote:Have you opened up the old pump yet?
I am thinking that if there is visible damage then maybe you have "swarf" in your rack?
I dont know if there is a filter of any sort in the PAS system?

No. I`m still at project phase of "mount my bench vice onto my bench" before I can open up the old pump...

But yes, there is a filter in the bottom of the reservoir. I back-flushed that and made sure it was unobstructed. No swarf came out, just a bit of sludge, but nothing really worrying.