Let's talk Power Steering Pumps

[BillyCorgi]

There is not a deducted Technical section for this topic, so........

Tme for a talk about Power Steering Pumps. After rebuilding as many as we have we get to see things…….

Today, we opened-up an exchange power steering pump return received from William out Mount Gravatt way. Beautiful condition pump, near new looking internals, shame that the front oil seal leaked and took out the ball bearing behind the pulley on the power steering pump.
Subaru use SHOWA brand power steering pumps on most all turbo engines. There are two model configurations, one with the high-pressure outlet pointing upwards (which we refer to as Top-Outlet) and the other with the high-pressure outlet pointing horizontally sideways (which we refer to as Side-Outlet). The top-outlet pumps were used on the 2.0 litre WRX and the side-outlet pumps mainly used on the 2.5 litre WRX& STI, the BL/BP Liberty/Legacy/Outback Turbos and the later 2.5 litre Turbo Foresters. William’s exchange return is a top-outlet SHOWA power steering pump.
As stated, it was a shame to see a good condition pump requiring replacement with such little wear. The most common failure mode for the SHOWA power steering pumps is by failure of the front oil seal. When the oil seal leaks the leaking fluid passes through the ball bearing, washing out the bearing lubricant in the process and making the bearing run “dry” and sing its head off.
There are two failure mechanisms that we can see for the premature failure of the front oil seal. One is that the oil seal is located behind the ball bearing and is shielded from airflow that may otherwise regulate the oil seal’s temperature rise. The second is what we find disturbing from a product quality perspective, is that the oil seal is not pressed “home” at the factory. In the case of William’s power steering pump, the oil seal was in contact with the rear metal shield of the ball bearing. The heat produced from the bearing is transferred into the oil seal through its contact with the shield and the rubber in the oil seal deteriorates at an accelerated rate.

When we rebuild a power steering pump the new oil seal is pushed in by hand force only (I have strong thumbs) and pushed home. Clearance to the bearing is confirmed before inserting the shaft with new bearing.

Enjoy!

MORE:
William’s power steering pump is going through the refurbishment process right now.
Internal clearance has been adjusted from 0.015mm to 0.020mm.
The inner side plate has had 0.005mm polished from the face to remove all vane marks. The rear cover has also had 0.005mm polished from the face to remove all vane marks. Flatness has been confirmed by the Johansson gauge method. Note: 0.005mm is the limit of our measurement accuracy.
The power steering pump has been test assembled and the modulating cam ring is articulating flawlessly.

[BillyCorgi]

So, over the past weekend I had the “pleasure” of overhauling a SHOWA side-outlet power steering pump. The type used on BL/BP Liberty/Legacy/Outback Turbo models, later WRX STI and Late XT Foresters.

I hate black painted power steering pumps. I hate PS pumps that have previously been serviced by others. Finding a pump that has previously had invasive service means extra work and additional time making good the work previously performed by “others”. Much rather have a ‘virgin’ factory pump every time. Most times black painted pumps are simply removed from a vehicle at the wrecking yard, cleaned, painted black and put on the shelf to be sold to a future unfortunate customer.

Sometimes black painted pumps have a seal kit put through them and then on-sold through a parts distribution network.

This pump had obviously been serviced by “others” previously. Serial Number “GB537” had been letter-punched into one side of the PS pump and another serial number “AD819” hand engraved on another face of the PS pump. There was evidence of the PS pump once being painted black, something common with whoever does the GB537 work. The black paint had been sand-blasted off with traces of the black remaining in places that the sand-blasting could not reach.

Now the fun begins. Time is going to evaporate while previous service abuse is remedied. Every threaded fastener/cap/plug on the PS Pump appeared to have been tightened with an impact gun. The M8 screws holding the PS pump body together should not require a 600mm breaker bar to loosen. One of the plug caps would not budge and required a 24mm A/F nut to be welded to it to get sufficient bite to remove it. The other cap would not loosen without a persuading shot with a cold chisel. The M8 screws required their thread chased with a stock & die. A plug tap was run down the M8 threaded holes. I suppose whoever did this abusive work considered themselves a tradesman?

Not knowing what had been done previously we set about measuring up all the key parameters of the PS Pump. The overall stacked clearance for o-ring compression was measured at about 0.25mm which we adjusted back to 0.20mm The clearance for the modulating cam ring was adjusted to between 0.015mm to 0.020mm. A minimum amount was lapped off each face of the vane pump sufficient to enable a flatness determination to be made.

After checking and confirming everything we were able to confirm the clearances were correct within our specifications and the modulating cam ring would articulate cleanly in service.

We were told by the workshop that commissioned this work that the PS pump had come from a “MRT car”. It is not known whether this meant an ex-MRT staff car or a car previously serviced by MRT. I wonder why the PS pump that appeared that it may have been serviced twice before required replacing another time?

[BillyCorgi]

POWER STEERING PUMPS - Episode 3…..



If there is something that I hate more than “black” power steering pumps it is “knock-off-copy” aftermarket pumps

We were contacted by a new customer who wanted some power steering pumps rebuilt. He had four PS pumps form WRX; a KYB pump from an earlier WRX STI; two Top-Outlet SHOWA PS pumps from mid-2000s WRX plus another WRX top-outlet pump which we concluded was an ebay knock-off-copy special.

Should it be sent with the others? We agreed that is should be sent and that it would be torn down for assessment.

The package of four power steering pumps arrived and indeed, the suspect PS pump was a knock-off-special typical of the low cost power steering pumps available on (for example) ebay. It was obvious that it was an aftermarket pump. There is no SHOWA name cast into the body. The rear cover is black cast iron rater that aluminium alloy, the Hex Key Cap on the side was 8mm hex rather than 10mm hex.

The pump was supplied as a used part and reported to have come from a Wise auto shop out Wangara way.

Digressing slightly for a moment, the Subaru power steering pumps are a precision machine. They are made to exacting tolerances and engineered in both design and manufacture to provide years (and kilometers) of reliable trouble-free service. CorgiWerx records the dimensional details of every power steering pump that is rebuilt, so we have a good statistic of the dimensional variability (and lack of it) of the power steering pumps. If this knock-off-copy was going to be a candidate for a rebuild we needed to ascertain whether is was any good for doing so.

Upon disassembly, one of the first thing we noticed was that the apex seal on the modulating ring (which controls pump displacement and output pressure) was missing. WTF? The quality and finish of the modulating ring was not of a standard equal to that of the OEM SHOWA pumps. The side plate of the vane pump was marked consistent with the vanes not being seated correctly when the pump is assembled, and the edge of the van will dig in and score the pump when the rear cover bolts are tightened. This is something we quite often see on the JKC pumps used on EZ30 H6 engines. We have our own proprietary assembly process to prevent this from occurring.
Next, time for taking the critical measurements.

The internal stacked clearance of all the components was measured as 0.50mm compared to the typical OEM stacked clearance of 0.25mm. So the components are not made to the same precision.
The rear cover was noticed to be a sloppy fit in the main body. No slop is observed in the OEM unit. The fit was measured as 62.65mm into 62.80mm bore where the OEM is 62.8mm into 62.8mm bore. The location and fit is important. The shaft of the pump runs in bushes located in the main body and the rear cover. Any slop in the lactation of cap to body will lead to misalignment of the bushes.

The pumping part itself consists of…..
(i) an outer ring that sets the overall width of the vane pump;
(ii) a modulating ring that must move within the space created by the outer ring (to control pressure);
(iii) a rotor that must spin inside the modulating ring within the space created by the outer ring;
(iv) Vanes which must slide freely in the rotor but not protrude out beyond the rotor (so as not to score the pump side plates).

The sizes of the components are critical and are all “Goldilocks” dimension, just right for the PS Pump to operate correctly.

The width of the outer ring was 19.04mm compared to the OEM also of 19.04mm, So the pump should have the same capacity.

The width of the modulating ring was 19.005mm compared to 19.025mm of the OEM. So the fit of the modulating ring is less precise. Sloppier and will allow greater fluid blow-by during pumping.

The rotor width was 18.985mm compared to 19.01mm of the OEM, so pumping would be less efficient.

The width of the sliding vanes was 18.98mm compared to 19.00mm of the OEM.

All in all, the copy is just not made to the same tolerances and same high standards as the OEM. We have concluded that it is just not economical to correct all the clearances back to OEM standard and that the pump will be scrapped.

[BillyCorgi]

POWER STEERING PUMPS - Episode 4…..

So, of the package of power steering pumps sent to us for rebuild (refer Episode 3) it came to pass time to work on the fourth pump. All done in no particular order. This was a Top Outlet SHOWA pump for a WRX. Its only distinguishing mark was that it was a very early pump of that series and it was as grubby as all F.

We started stripping it down and when we went to remove the pressure modulating valve it would not move. It was stuck in there tighter that a fish’s whats-is-name and would not budge. It was obvious that the power steering pump would not work as there was no way that the pump’s output pressure could be controlled with a stuck-tight valve. We tried long nose pliers. Could not get a sufficient grip. The jaws of the long nose vice-grips would not go into the hole to get hold of the valve. Should we drill a hole in the end of the valve bore and knock it through? This may have destroyed the pump body. Finally a way to wedge it out we invented and the valve, reluctantly, was extracted from the pump body.

With the valve out we looked it, inspected it, measured it. There were no signs of debris that may have jammed the valve nor signs of score marks on the valve that debris would have made? So a piece of clean cloth was judiciously inserted in to bore to search for “bits” however the cloth came out clean. Then we tried to put the valve body back into its bore in the pump body, but no could do. Next a clean pump body was taken from the “bucket-of-bits-that-you-cannot-throw-out” and with its spring, the valve was inserted into the spare pump body. The valve moved and jiggled up and down against the spring just like it should. Retry the valve back into its original home and…..no can do! Conclusion, the power steering pump body is warped.

We measured up everything that we could and concluded that maybe the body from the ebay knock-off-copy special (Episode 3) may be a candidate for resurrecting the pump. That is, to build everything from the OEM SHOWA pump into the body of the knock-off unit.

The options were put to the customer. The pump is warped, we could…..
(1) Junk the pump
(2) Rebuild the pump into the body of the knock-off
(3) Rebuild the pump into the CorgiWerx “spare” OEM pump body (with additional charge)

The customer elected the third option, as for a rebuild, it came with the lowest risk. OEM parts back into an OEM pump body.

So, with the decision made, every critical measurement was taken, all clearances were checked and recorded, correct movement of the modulating ring confirmed and the pump wrapped and packed for return to the customer.
The customer later advised that the pump came from a privately purchased JDM engine with a cooked as toast turbo. Maybe there was more than a just cooked turbo.

One more day in the life of CorgiWerx.

[BillyCorgi]

POWER STEERING PUMPS - Episode 5…..

"If you know, you know!"

[BillyCorgi]

POWER STEERING PUMPS - Episode 6…..
Did I ever say that I hate aftermarket Power Steering Pumps? Well, let me set out my case.

Recently, a young gentleman brought to us a power steering pump that was the wrong power steering pump for his vehicle and that we knew would be an aftermarket pump. Let me set out what is wrong with this aftermarket pump.

If you remember Episode 3, we reviewed how a typical power steering pump is constructed and discussed the critical internal clearances required. Pictured are these components from the sample aftermarket pump received.
A is the rear cover which forms one side of the vane pump.
E is the internal plate which forms the opposite side of the vane pump.
B is the outer ring which forms the width of the vane pump
C is the modulating ring which moves within the outer ring (B) to control the pump pressure
D is the rotor which holds the vanes and rotates within B & C to pump the fluid.



Measuring around the diameter of the outer ring (B) we measured 16.025mm / 16.030mm / 16.015mm / 16.020mm / 16.015mm. The outer rind is not flat. Typically, on an OEM pump the width dimension would be constant around the full circumference of the ring.

The modulating ring measured a consistent 16.025mm around its circumference.

The rotor measured 16.015mm.

What is evident is that the gap between the two side plates of the vane pump is not flat and that the width created is in places thinner than the modulating ring. Typically, 0.02mm clearance is required for proper movement of the modulating ring. There is no evidence that the modulating ring ever moved. Fresh out of the box the modulating ring would have been bound up and the aftermarket pump would not have worked correctly.

Next, the gap for which the rotor to rotate is too small with insufficient clearance for lubrication between the rotor and the sides of the vane pump. If you examine the images of the rotor (D) and the internal plate (E) you can see that there has been metal to metal contact between the rotor and the inner plate with tearing of the inner plate surface and metal transfer from the inner plate to the rotor.

The dimension were incorrect, the clearances were insufficient, the pump would not control pressure and the internals of the pump began to destroy themselves.

[Ric]

Couldn't see the whole photo on my screen (unless you click through to the original image.)
Here's a slightly reduced copy

smaller-pump.jpg (138.74 KiB) Viewed 2428 times

[BillyCorgi]

POWER STEERING PUMPS - Episode 7…..
"So, is this your work?"

Someone out there playing along at home is responsible for this.

A WRX power steering pump recently returned on exchange from a workshop customer. Reported to have come off someone's recently purchased pride and joy that got defected for a horrendous power steering pump fluid leak.
May we say that laying into the high pressure outlet fitting with a hand held angle grinder does not improve the seal on the high pressure banjo fitting..
Whoever did this fine artwork I am sure was present at their parent's wedding!

Presently seeking the culprit to return the hex fitting as a suppository!

[BillyCorgi]

POWER STEERING PUMPS - Episode 8
"Product Knowledge"

So yesterday we were contacted by a young man seeking advice about his Gen4 H6 Power Steering, saying "the power steering system on my H6 has had a full meltdown, had all the fluid come flooding out of the reservoir and when I started the car up there were some not nice noises coming from the pump".

We advised him that he had a horrendous air leak and air was being sucked into the fluid circuit causing frothing of the PS fluid. We advised his to begin by replacing the rubber inlet hose and replacing the inlet fitting o-ring.

We advised him that a simple service act like replacing the air filter can disturb the PS inlet hose and set this situation off. The hose clips into the side of the air filter box, so it can easily get disturbed when changing the air filter. The old hard brittle inlet hose is no longer flexible. When the air filter box is disturbed the hose is also moved, which disturbs the connection of the hose to the inlet fitting at the pump and sets of an air leak.

The young man advised "Yep I just happened to have replaced it"

CorgiWerx product knowledge.

The attached image shows how the power steering inlet hose from the reservoir to the pump clips into the the air filter box. Designed by Subaru to get CorgiWerx more business?

[BillyCorgi]

POWER STEERING PUMPS - Episode 9
"The Black Power Steering Pump"

So I was dropping off some rebuilt power steering pumps to a workshop customer and the proprietor asked me to take two Liberty GT-B power steering pumps back with me for rebuild. When the pumps were boxed to hand over to me the technician who removed one of the pumps mentioned to me “I know that you don’t like black pumps…..”

So, I do not like black pumps? Let me set out my case.

The black pump given to me for rebuild by the workshop mentioned above creates a conundrum. “Why does a rebuilt power steering pump, by virtue of it being black and having a stamped serial number, require another rebuild?”
The black pump has been stripped and examined and we will go through what is typically found with these pleasantly pigmented pumps in the attached photographs.

Photo #1 shows the serial number stamped into the end cover of the power steering pump. LH054. Note the peeling paint. Why paint the pumps black if the paint is prone to shedding?

Photo #2 is showing the oil seal. It is difficult to show in this shot, but the oil seal is not inserted fully “home” and is proud of its bore. This is also an assembly weakness (or failure?) with the PS Pump from the factory. The oil-seal sits proud and contacts the ball bearing. The contact transfers heat from the ball bearing to the oil seal shortening the seal’s service life.

Photos #3 & #4 show the condition of the internal components of the black pump. While the wear is relatively low, it is evident that no remedial work has been performed on the pump.
The original wear marks present on the pump before the black rebuild are still present. They are highlighted in dashed Red circles.
The left item in Photo #3 vane wear marks still present.
The right item in Photo #3 is an identical component of a CorgiWerx refurbished pump after the has been lapped to remove all vane wear marks and imperfections.

When CorgiWerx rebuild a “virgin” power steering pumps a datum is noted on the rotor, each vane is removed in order, the vanes are kept in correct orientation and in correct order from the datum. Upon reassembly each vane is correctly oriented and placed back into the slot of the rotor from which it originally came. We do not know if this is not required, so we will continue to do this as it costs nothing to do it. Quality costs nothing if it is correctly designed into the process.

Photo #5 is the vanes removed from the black pump stacked in order of removal from the rotor and oriented as they were removed. There are eleven sliding vanes. Each vane identified with a red arrow shows the vanes that were installed upside-down during the assembly of the black pump. All vanes were assembled with the correct face of the vane pointing “outwards, however seven of the eleven vanes were inserted upside down.

Lastly, Photo #6 shows the test CorgiWerx perform after lapping each face of the vane pump. To test and confirm flatness, the two cleaned faces hold together against gravity with just the suction bond created between the two flat faces. Just like Johansson gauge blocks. (Google it if you are not familiar with gauge blocks).
After cleaning both faces and just wiping over the faces with clean fingers, the minute amount of natural oil transferred though the finger prints is sufficient to create a suction bond to hold the parts together against gravity.

So, I do not like black pumps? Well, I do not see that they represent value for money.

[BillyCorgi]

POWER STEERING PUMPS - Episode 10
""Quality Is Free"

We are refurbishing a customer's 9.6cc/rev JKC Power Steering Pump from a early Forester GT. The pump is a "virgin" unit that has not previously been serviced.

The first photo shows the internal components prepared for assembly. The internal Side Plate "A" has been lapped and 0.015mm removed to clean-up the wear marks. The Rear Cover "B" has had 0.01mm removed to clean-up the wear marks.

The Modulating Ring "D" has been set to 0.02mm thinner than the Outer Ring "C" which sets the internal width of the power steering pump.

The Rotor "E" is 0.03mm thinner than the Outer Ring, this being the factory clearance dimension for the rotor.

"F" is the stack of the removed vanes oriented in the direction they were removed and ordered left-to-right in a clockwise direction from the datum on the rotor. The datum mark on the rotor may be seen at the 12 O'clock position on the face of the rotor.

The second photo shows the vanes stacked in order and the datum marked on the holding tape. The image shows the consistent wear pattern on the forward face of the vane during normal operation.

The third photo shows the reverse side of the vanes being the rearward face of the vanes during normal operation. These marking may be compared the the jumble of vane markings from the Pleasantly Pigmented Pump featured in the previous Episode#9.

Each vane was reassembled back into its original position in the rotor and in its original orientation.

"Quality is Free" when it is designed into the process.

[BillyCorgi]

POWER STEERING PUMPS - Episode 11
""The Faulty Oil Seal Installation"

You will recall that I have commented on the oil seal not being inserted fully "home" in the SHOWA Power Steering Pumps. This is a known factory weakness and something we also observe on the "pleasantly pigmented pumps"

Occasionally we see the bearing being damaged through the interference contact with the oil seal. The photo here is from a genuine SHOWA WRX pump stripped today for inspection and rebuild. Here, the oil seal was proud and protruding into the bearing with sufficient force to dislodge the inner shield from the bearing. The shield was stuck to the oil seal. The heat transferred into the oil seal was sufficient to make the oil seal begin to vulcanize to aluminium pump housing.

The oil seals are inserted fully "home" on a CorgiWerx pump and then the oil passageway to behind the oil seal check to confirm that is free from obstruction.

[BillyCorgi]

POWER STEERING PUMPS - Episode 12
"The incorrect aftermarket rebuild"

So, on a rainy afternoon we were in the Corgi Kennel preparing power steering pumps for a workshop customer. Half way through the batch of PS pumps we were working on we were dismantling a pump for service and removed the rear cover of the pump. This is what we found.

Note the identification marks on the modulating ring. These identification marks face forward in the PS pump. In this case the identification marks are facing rearwards. During previous invasive service the modulating ring had been installed backwards, reverse and in the incorrect orientation.

You may be able to see that the modulating ring is eccentric. In this position, the PS Pump would not have achieved full capacity and may have suffered from power assistance "drop-outs" under load.

When this was shared with Miss Heidi she was very unimpressed!