Power Steering Pump

[Alistair E]

Does anyone have any details on the internals of the pas pump? I've now got the pump off the car and have split it into it's three main body parts. However, I still can't see anything wrong. No bits of spare metal flying around.
The pump was rattling, not groaning. The fluid level was fine and there were no visible leaks. The spindle feels fine to turn, no bearing grating. There is no sidewards play in the spindle, but there is endfloat. I don't see how the endfloat could cause the rattling.
Does anyone know exactly how the pump operates? From what I can see, there are three hose connections, a floating-vane fan and a spindle with a cam which operates two pistons. I haven't tried to split the pump any further than this. Maybe there is something more I need to strip down in order to see the problem.

Any advice gratefully received.

Alistair

[91_S2]

Finally somebody attacked one of these and tore it down. Mine clatters - like valve clatter or rattling might be close - but it is too cold to tear it down just now. Be interested to hear what you find out.

[s2driveruk]

I seem to remember there was an exploded diagram of a p/s pump in a Haynes manual for the 80, 90 and Coupe.

Cheers,

David

[Graham]

If there is end to end float wont the spindle with the slots for the vanes in it have side to side clearance allowing leakage??

[Alistair E]

David
The diagram in Haynes is not the same pump, although quite similar. It doesn't have the cam on the spindle with the two pistons. I've attached a pdf file of the actual pump. Still don't understand exactly how it works and my pump is with a hydraulic company for them to have a look at. It would be helpful to have it in my hands to compare to the diagram.

Graham
Do you mean external leakage? There was none. The spindle is splined and fits into an splined disc which has the slots cut into it for the vanes. Hope that makes sense. This disc, about 10mm thick (guessing from when I had the pump in my hands), is held in place by a cover plate/chamber which is clamped up between two sections of the pump body. I don't think endfloat in the spindle would cause endfloat in the disc. I can't see how the endfloat would cause the noise, but I just can't see anything wrong.
Hopefully the hydraulic co. may have more of an idea.
Apologies to everyone for my appauling description of the internals of the pump. Just can't think of any better words to describe them.

Alistair

[Graham]

The 2 pistons must be an intensifier unit for the bomb as a vane pump is limited in its pressure output but high in flow (for steering etc.)where as a piston pump is much more suited for developing pressure with low flow capabilities (brakes etc). So does one hose go to the bomb and the other go to the steering? If this is the case then the chances are the line to the steering comes from the vane pump and the line to the bomb comes from the piston pump. So the unit is a twin pump, both pumps independant of each other except for drive and supply. The rattling might be off the pistons, see how much play they have within their bores also there must be a valve setup for a piston pump, one input valve and one output valve, (probably spring loaded so one opens on suction and one opens on compression as the drawing below indicated). Hope this helps

[s2driveruk]

yes there is a line off the pump direct to the bomb

[Alistair E]

Graham

Would appear to be as you describe. The line for the bomb comes from the piston end of the pump. The two other lines are one from the resevoir and the other disappears towards the bulkhead which I assume is the one for the steering. You may be right about it being the pistons. I haven't checked the play in the bores yet, but I do get the brake warning light just after starting the car after it has stood overnight. I suppose this could be low assistance from the pump. If it is play in the bore, I guess I'm looking at a new pump. Can't see how you could repair it unless you could have oversize pistons made.

Alistair

[Graham]

Take it to a hydraulic specialist who will re-seat the valves, and possibly even make a new piston for them out of phosphor bronze or cast iron (both self lubricating metals), or have the bores sleeved. I work as main fitter in the heavy hydraulics department on Teesside Corus site, so have problems like this quite often. If the valves are not machined discs they could be something as simple as ball bearing check valves, one in one out. If anyone has an old fooked one i might be able to get it overhauled for (dirt)cheap. Do a strip down overhaul Guide. As long as the vanes are plastic/bakelite,(metal vanes wear the bore quicker) and the bearings can be removed it should be straight forward.

[waveydavey]

Take it to a hydraulic specialist who will re-seat the valves, and possibly even make a new piston for them out of phosphor bronze or cast iron (both self lubricating metals), or have the bores sleeved. I work as main fitter in the heavy hydraulics department on Teesside Corus site, so have problems like this quite often. If the valves are not machined discs they could be something as simple as ball bearing check valves, one in one out. If anyone has an old fooked one i might be able to get it overhauled for (dirt)cheap. Do a strip down overhaul Guide. As long as the vanes are plastic/bakelite,(metal vanes wear the bore quicker) and the bearings can be removed it should be straight forward.

Graham. Let me know how you get on with this possible rebuild. My PS pump is chattering and although I'm going to try a fluid change I am expecting the worst.

I am quite local to you. I live in Ingleby Barwick and work as a freight train driver. I normally visit the Lackenby railway grids several times a week. The sight of the slag ladles being tipped out near the BOS plant during the middle of the night really is something special to watch.

[bob69]

I have the very same problem and it seems worse when cold, noise like a rattle which dies down as engine warms up, i was going to get a new one sometime in the new year but if it can be easily reconed i would certainly be interested...
Mine had been leaking ever since I bought the car until one day it dumped its contents all over the engine bay but sorted that thanks to this forum and this thread http://www.s2forum.com/forum/showthread.php?t=4138 cheers all who helped...

[Alistair E]

Take it to a hydraulic specialist who will re-seat the valves, and possibly even make a new piston for them out of phosphor bronze or cast iron (both self lubricating metals), or have the bores sleeved. I work as main fitter in the heavy hydraulics department on Teesside Corus site, so have problems like this quite often. If the valves are not machined discs they could be something as simple as ball bearing check valves, one in one out. If anyone has an old fooked one i might be able to get it overhauled for (dirt)cheap. Do a strip down overhaul Guide. As long as the vanes are plastic/bakelite,(metal vanes wear the bore quicker) and the bearings can be removed it should be straight forward.

Graham

Tried to get the plugs out which keep the pistons in, cross head plugs. Just a bit tight. I read a bit on another thread which said that some people have used a hammer and chisel to get them started. Not sure if that's such a good idea, but may have no choice.
Problem with getting hold of an old unit is that they are an exchange item with a £50+ surcharge.
If I have no joy with the plugs I think I will have to bite the bullet and by a new one. There was one on e-bay recently but the seller refused to sell after the auction finished. Said he thought he had set a reserve price but it didn't take effect.
I'll keep you informed.

Alistair

[Graham]

My pump is ok at the moment, so i dont have a spare to work from, but i have sent a few e-mails to specialists to see what they can come up with. If they return nothing i will twist the arms of a few reps at work, or strip it down myself, overhaul it and rebuild then test it at work- boss wouldnt be too happy though, were very busy at the moment.

[Jas11n]

Graham

Tried to get the plugs out which keep the pistons in, cross head plugs. Just a bit tight. I read a bit on another thread which said that some people have used a hammer and chisel to get them started. Not sure if that's such a good idea, but may have no choice.Alistair

I used the hammer/chisel combo to remove one of those leaking plugs, works fine,,,,,,,,,,,,,but later found this tool which is better to use..

[Alistair E]

Bleeding the pas & bomb hydraulics

Does anyone have a guide on how to bleed the system after the pump has been removed?

Thanks

Alistair