W124 vickers power steering pump ticking noise.

[peter gibbs]

Vickers Power steering pump 124 460 18 80 non tandem fitted to 124.007/026/027/030/050/090/031/051/091 and 129.060/061.
On high mileage cars this pump can produce a ticking noise, which is perceptible at idle.This is due to wear on the shaft and or impeller splines. There is also end play on the shaft of about .4mm.
When you have the pump apart you can see that there is movement both radially and laterally of the impeller on the shaft. By manipulating it in your hand you can hear the ticking noise which is evident when it’s in the car.
MB have deleted both the shaft and impeller from available spares even though reseal kits are still available. What do you do? Throw away the pump away? Here is a fix which worked for me.

1) We don’t know if the pumps had shaft end play when they were new. Others seem to agree that they all have end play. It is my opinion that the end play, which in effect is the shaft sliding in and out of the impeller, is the source of the wear. Is this a design fault? You’d assume that Vickers know what they are doing. BUT, if any other items of hardware driven by the serpentine belt had end play we would usually pronounce it as buggered.
2) I have not been able to determine whether the wear is on the external shaft spline or the internal impeller spline. It could be both. They both appear undamaged to the eye.
3) Any movement either laterally or radially of the impeller on the shaft will produce the ticking noise so, in my opinion, you have to eliminate both.
4) If you have a pump which doesn’t have the ticking noise then the insertion of shims to eliminate the end play may well be a preventative if you have the pump apart to reseal it.
5) On two such pumps I examined, there was a remarkable lack of wear on the main shaft bush. They were perfect in both cases after high mileage. Therefore the shaft is not wearing in this area also. Ditto for the two thrust plates either side of the impeller. I assume these are made from something slippery like valve guide material which is usually manganese bronze. Remarkable condition given that the impeller has been rubbing against them all these years. There was no perceptible wear ridge. Again, there was no problem with the impeller cage or vanes. The only wear appears to be isolated to the splines.

Here are the issues related to the fix.
1) Make sure you have replaced the main shaft seal in the pump housing before following the steps below. The impellor will be very well bonded to the shaft. I’m told it is possible to separate the impeller from the shaft with a fine point blow torch in the future. However the original seals have lasted 30 years!
2) Shim washers, inserted on the inner end of the shaft, under the snap ring will take up the end play. If you are replacing the snap ring then its thickness will also have to be taken in to account with this calculation. The original snap rings are quite thick (1.2mm) and I could not find replacements of this size. Trial and error until a snug fit is obtained will suffice. The usual end play is about .4 mm. I can’t believe how difficult is to source things like shims washers. None of the car/engineering suppliers near me had any. In the end I found them on the internet here https://www.minibearings.com.au/and they sent them overnight. The problem is that they only come in sizes which are not entirely suitable for this application and have to be modified. The shims needed are 10 mm I.D. (shaft size), but they only come in 16 mm O.D. They have to be modified. The whole thing is dictated by the rear thrust plate. See attachment https://ozbenz.net/download/file.php?mode=view&id=30368 The projection and diameter of the rear of the shaft together with the shim washers and snap ring must fit into the recess of this plate without touching. As the shim washers are 16 mm OD, you have to reduce them down to about 12.5 mm dia. which is about the same as the snap ring. I did this quite easily with a fine tooth mini file. It doesn’t have to be perfect. They just have to fit into the plate recess and not touch when the shaft is spinning. Likewise, the snap ring. The diameter of the plate recess is 13.5 mm and the depth is 3.8 mm. The projection of the shaft from the impeller with shims and snap ring attached worked out to be 3.19 mm.
3) To eliminate the movement of the impeller on the shaft , I used Loctite 660.https://ozbenz.net/download/file.php?mode=view&id=30367 (attached).

DSCN0112.JPG

Again, I had to order it, this time from Repco, in a 6ml. tube. This is amazing stuff, engineered for precisely this type of worn spline application. It is a thick, metallic looking paste, anaerobic curing in about 10 mins (work time) and full strength overnight. Assembly is critical. You have to get it together, all screwed up before the Loctite dries so that the impellor is exactly in the right position on the shaft, between the two manganese bronze plates, when the Loctite cures. So you have about 10 minutes to do this. I cleaned both splines with brake cleaner and iso alcohol. You fit the shaft into the housing first. The Loctite is only put (liberally, fill the splines) on the inside splines of the impeller so that when it is pushed home on the shaft, the excess comes upwards so you can wipe it away before putting on the shims and snap ring. You don’t want any Loctite debris on the end of the impeller chamfer that faces the front of the car. Make sure this is wiped away first before pushing on the impeller. Quickly assemble the pump and tighten the four bolts. Be careful not to turn the shaft for a couple of hours. Allow to cure overnight then reinstall the pump.

[Bartman4800]

This problem is in the realm of hydraulic pump repair.

By the way, here is a teardown video by MercmadWA:
https://www.youtube.com/watch?v=Ix_LXmB8XwU

Vane pumps such as this one have virtually no load variation (during one revolution) due to its nature.
Therefore the spline should not have flogged out over time.
I would have expected the bearing bushings, housing, end plates or the vanes and rotors to wear out first.

Obviously you kept the hyd power steering fluid very clean and in service condition, which is why the rest of the parts are in good condition.

I cannot explain the issues you found, but you dealt with it very nicely!

Thanks for the writeup.

Regards, Bart

[peter gibbs]

Thanks Bart,
I have been liaising with MMWA about this. He has had two pumps which don't show this and I have had two pumps that do! Go figure. I made videos of the noise at idle and the shaft/impeller movement but unfortunately you can't upload videos on the Ozbenz site. I did post it on FB W124 Australia, if you're a member, with the videos.
Peter.

[CraigB]

Thanks for the tip off and the write up

[Bartman4800]

Thanks Bart,
I have been liaising with MMWA about this. He has had two pumps which don't show this and I have had two pumps that do! Go figure. I made videos of the noise at idle and the shaft/impeller movement but unfortunately you can't upload videos on the Ozbenz site. I did post it on FB W124 Australia, if you're a member, with the videos.
Peter.

As an engineer, I have the feeling there are some quality issues at hand here, with the too large tolerance variations. Like I said, splines should not flog out, if they have the correct clearance. But if they don't, then all bets are off...

Also, I wonder why Mercedes would use an English brand like Vickers...

[peter gibbs]

Well, I did wonder that. I honestly can't figure out why they didn't factory install shims to take up the end play. Vickers were aircraft engineers. You'd think they'd know what they were doing. Suppose every one has a bad day.

[Bartman4800]

Shims are only needed if you cannot control your manufacturing tolerances close enough.
After the parts have been made, It needs a human to measure what the clearance is, then add the correct amount of shims.
Nowadays, tolerances are so tight that everything fits out of the box, using CNC production techniques and laser measuring of parts.

So no modern designs should contain shims. I used to split moped engines when I was young, that were full of shims. This happened with italian and German brands like Puch, Aermacchi and Zundapp. Then the Japanese came with tighter production tolerances (Yamaha, Suzuki, Honda and later Kawasaki) and shims were a thing of the past.

Same thing used to happen with pistons in an engine block. You obviously cannot shim these, but they were paired. So a human would measure the bore and look in the crate of pistons until one was found that would fit without too much slop. That would obviously lead to quite a bit of difference between individual engine output - the Monday morning product....

And yes they could have shimmed the end float in your pump, but no way they could have decreased the slop between the male and female spline if the parts were out of tolerance...