Power Steering Pump Question(s)

[Jordan]

Other than the hub (and pulley), is there any difference between the pump with the conical hub and the one with the straight hub?  Are they interchangeable if you have the correct pulley for the pump.  That is, can I swap a pump and pulley with a straight hub with a pump and pulley with a conical hub?  Is the mounting the same?  Appreciate any insight on this.  Thanks.

[Jordan]

So no one has swapped pumps?  Is one pump considered better or more robust than the other?

[Pawel66]

From parts lists analysis the difference is only mentioned as for the pump itself and the pulley (and washer+nut for the pulley), nowhere else. The bracket is one part number the whole time, regardless.

In parts list it also adds necessary components when you go from straight to conical type of pump - and here the pulley, washer and nut are added, nothing else.

[Jordan]

From parts lists analysis the difference is only mentioned as for the pump itself and the pulley (and washer+nut for the pulley), nowhere else. The bracket is one part number the whole time, regardless.

In parts list it also adds necessary components when you go from straight to conical type of pump - and here the pulley, washer and nut are added, nothing else.

Thanks Pawel, where do you see this info?  I am assuming from what you are saying that the straight hub was the initial design and was changed to the conical hub.  Does it indicate when this change occurred? 

[Pawel66]

This is from the digital parts catalogue, today called B2B Connect.
No information on when the change took place.

Funny thing is: PS pump today is gone from the catalogue. When I was looking it up a couple of days ago, it was where it has always been, under Air Compressor. Today it is gone. What is left is the box with hoses, etc. Under Steering. But only that.

[Pawel66]

Update: I opened the system again, and PS pump was back where it was before - under Air Compressor, but for the 250SL, gone from 280SL. It also appeared in 230SL under Power Steering.

What I found while looking at it for 113042 (you always have to check across the types, there are various pieces of information under various designations) is:

A 127 466 03 15 PULLEY (CONICAL BORE)

FROM ENGINE
129.982 10/50,12/52 000057
129.982 20/60,22/62 000046
130.980 10/50,12/52 000076
130.980 20/60,22/62 000070
130.983 10/50,12/52 000057
130.983 20/60,22/62 000046
130.984 10/50,12/52 000076
130.984 20/60,22/62 000070

And also

FROM ENGINE
129.982 10/50,12/52 000057
129.982 20/60,22/62 000046
130.980 10/50,12/52 000076
130.980 20/60,22/62 000070
130.983 10/50,12/52 000057
130.983 20/60,22/62 000046
130.984 10/50,12/52 000076
130.984 20/60,22/62 000070

PART IS ONLY OR ALSO SUPPLIED AS RECONDITIONED PART

These numbers do not make sense. "As of" engine numbers are the same for 250SL and for 280SL. I do not understand it.

[Jordan]

Thanks Pawel.  So it looks like the conical hub was introduced sometime during the 250SL production.  All 230SL's should then have the straight hub and a certain number of the first 250SL's.  I wonder why they changed it because the pump design didn't change?  Was the conical hub more robust or was it a cost saving somehow?  As you say, the two pumps are identical except for the hub, and of course the centre of the pulley that slides onto the hub.

[Pawel66]

I am not sure what the numbers mean, could it is like you are saying.

Why go conical? I am not educated enough, but one thought that comes to mind: complaints form service centers. I think it is much easier to remove pulley from conical shaft.

[Jordan]

Why go conical? I am not educated enough, but one thought that comes to mind: complaints form service centers. I think it is much easier to remove pulley from conical shaft.

Pawel, your idea makes more sense.  It can be a bear removing the pulley from the straight shaft if it has rusted at all.  I'm going to assume therefore that the pumps are interchangeable, provided you have the correct pulley for the pump.

[MikeSimon]

A conical seat transmits more torque. The friction between hub and shaft is higher than with a straight shaft. You achieve a positive seat easier than trying to maintain the correct dimensions for hub and shaft on the straight fit.

[Pawel66]

Thank you Mike, I was curious about it.