PAS Pump end float

quattro

quattro

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Staff member
I have never had a PAS P6 before Sparky, so am new to this bit.

I am in the process of stripping out the engine bay to paint it and have removed the PAS pump. I have noticed a sqeak from this area when running so had a good look at the pump. This is around 1mm end play on the pulley wheel, is this right? Seems a lot to me

Richard
 
Hello Richard,

My power steering pump has seen 226,000 miles of service and it too has a degree of end float on the pulley. I noticed it years ago when I changed the original belt and again when the 4.6 went in. I dare say mine is more than 1mm but it does not seem to effect performance and there are no oil leaks (touch wood) from that area.

All the best,
Ron.
 
I think you'll find they're all like it, due to the way the pump is constructed, in that the drive shaft is free to float in the gears, and all the endfloat is on the shaft not the pump gears. As an example, if you had the same amount of play on the end of a V8 oil pump drive it would be a problem as the gear is fixed to the shaft, so the endfloat would have to be between the gear and the casing, causing loss of pressure.

The PAS pump is constructed that way for a good reason, anyone care to hazard a guess at what that reason is?
 
harveyp6 said:
The PAS pump is constructed that way for a good reason, anyone care to hazard a guess at what that reason is?
Click to expand...

To make it squeak?

Seriously though, to allow it a little movement to line up with the belt?
 
Hello Harvey,

I have never pulled one apart to have a squizz inside, so I won't take a guess at this stage. I'll have a look at an exploded diagram and then see if i can formulate an opinion. I'll come back within 24 hours.

Ron.
 
harveyp6 wrote,...
I think you'll find they're all like it, due to the way the pump is constructed, in that the drive shaft is free to float in the gears, and all the endfloat is on the shaft not the pump gears. As an example, if you had the same amount of play on the end of a V8 oil pump drive it would be a problem as the gear is fixed to the shaft, so the endfloat would have to be between the gear and the casing, causing loss of pressure.

The PAS pump is constructed that way for a good reason, anyone care to hazard a guess at what that reason is?
Click to expand...

Hello Harvey,

I am going to have a stab in the dark,....the pulley is located on the shaft by a cam, behind which the bearing is pressed. Within the pump body the shaft rotates on bushes. At the other end and turned via a pin which locates on the shaft is the vane carrier. The carrier however is not a press fit onto the shaft so when the shaft moves axially so the carrier remains unmoved without undue pressure being placed upon it. The shaft floats if you like within the pump body, untethered at either end. Because the pump body is composed of three sections each of which is sealed against the adjacent side by one or more 'O' rings, the main shaft must have a degree of axial movement built in to accomodate such a construction.

Now,...have I missed the street altogether.. :?

Ron.
 
Do you know that for one moment I thought you had it then, I was thinking it was too easy, but luckily enough the question still remains unanswered. Still plenty of time for more theories to be formulated. Good Luck.
 
Hello Harvey,

It is nice to know that I am almost there, or maybe I am but I chose not to mention one of the other points that was going through my mind. I don't like to guess, that is my trouble. Everything I know about P6 Rovers is self taught, a combination of reading, listening, experience and common sense. I am actually a mathematician who branched out whist studying electrical engineering at University, so I am good at thinking. Now thinking cap on... :?

I shall return.. :)
Ron.
 
I can't (and don't intend) to give clues as there aren't really any that I could give without giving the game away, but I will say that I doubt you will find the answer in a book, sitting there ready for you to find, but all the info you need is out there, and if you interpret all of that correctly you can't fail to reach the correct conclusion. Happy hunting!
 
quattro said:
Hopefully quite quickly so I can mend my pump :?
Click to expand...

I don't see that you have a problem, and the answer to the question isn't a cure for that or any other problem, it's purely why the pump is constructed in the way that it is.

If you had a problem that needed an answer, in particular if that answer was the one we're looking for I wouldn't be keeping it from you. The end float is there on all the pumps,because the shaft isn't fixed into the vane, the question is why.
 
harveyp6 said:
quattro said:
Hopefully quite quickly so I can mend my pump :?
Click to expand...

I don't see that you have a problem, and the answer to the question isn't a cure for that or any other problem, it's purely why the pump is constructed in the way that it is.

If you had a problem that needed an answer, in particular if that answer was the one we're looking for I wouldn't be keeping it from you. The end float is there on all the pumps,because the shaft isn't fixed into the vane, the question is why.
Click to expand...

Cheers harvey

Do they all squeak like that?
 
Are you sure the squeak wasn't the belt? If you can spin the pulley and it squeaks then it could just be the seal, but other than that without hearing the noise it's a bit difficult to say. In my experience apart from minor leaks I've found them to give very few problems.
 
harveyp6 said:
Are you sure the squeak wasn't the belt? If you can spin the pulley and it squeaks then it could just be the seal, but other than that without hearing the noise it's a bit difficult to say. In my experience apart from minor leaks I've found them to give very few problems.
Click to expand...

Very difficult to say, but it is definately coming from that area.

It only does it until I get moving then it slowly stops squeaking. If I park it up for a week or so, facing downhill, it squeaks, if it is on the flat, it doesn't.
 
harveyp6 wrote...
I think you'll find they're all like it, due to the way the pump is constructed, in that the drive shaft is free to float in the gears, and all the endfloat is on the shaft not the pump gears.
The PAS pump is constructed that way for a good reason, anyone care to hazard a guess at what that reason is?
Click to expand...

Hello Harvey,

Well I do like a good puzzle and as I have not had the joy (so far) of pulling a pump apart I am making this more detailed view based upon further studying the diagram and from reading the reassembly instructions.

Now as the pump body is composed of three parts and the shaft slides through the centre section supported by bushes, the bearing at one end and the vane carrier sliding onto the shaft at the other end, being located by a drive pin. If the vane carrier had to be pressed onto the shaft, that would make assembly much more difficult in that there would be a problem in ensuring it was not pressed on too far. If it was then the shaft would bind. If it was not pressed on far enough then the correct fitment of the end section of the pump and free rotation of the carrier would be compromised.

Dismantling the pump would also be far more difficult if the vane carrier had to be pressed onto the shaft as the centre section of the pump would see a bearing pressed on one end and the carrier pressed onto the other end. By allowing the vane carrier to slide over the shaft until coming to rest, the correct axial location is always assured. Axial movement of the shaft does not then compromise the rotation of the carrier.

The end float (or axial movement) is between the bearing and the end cover plate and is there to ensure that the bearing does not bind during assembly or under any operating conditions that may be encountered.

As I mentioned but did not elaborate on the shaft axial movment and the attached nature of the vane carrier in my first post,..I am hoping I may be closer this time?

Ron.
 
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