Power steering pump problem. Fixed, but still confused
Posted: Sun Dec 25, 2016 6:16 pm
Long story, attempting to be short:
Heard a squeak which gradually got louder and more frequent
Eventually investigated to find a power steering pump leaking, alternator covered in serpentine belt debris.
Replaced power steering pump with rebuilt pump(ac delco) Squeak persisted and the rebuilt pump leaked.
I tore down both pumps to see what was wrong. Bearings were fine, no play, ran smooth. Pumping elements were fine. Return screen to the reservoir didn't have any debris in it.
Both leaking pumps were leaking out of the front seal, which is actually just a grease seal for the bearing. It seems that if the internal lip seal that separates the input shaft bearing cavity from the vane pump cavity leaks, the bearing cavity receives pressurized power steering fluid which makes its way through the bearing and out the input shaft. I'm guessing that even if the pump is rebuilt, and the replace the seal without repairing any wear on the sealing surface of the input shaft to the pump, that it will leak.
So I bought a new, aftermarket pump, not rebuilt. The leak was fixed, but the squeaking was still present, and as bad as ever. Ensured belt tension was good. The only way to reduce the squeak was to run the belt very tight, which I did not want to do.
Finally checked pulley alignment to find that the power steering pump was sitting a bit over 1/4" ahead of the crank and alternator pulleys. It ran true, but was just uniformly shifted. The mounting bracket wasn't loose and definitely doesn't have 1/4" of play, and based on the debris on the alternator from the 1st pump replacement, i'm guessing that the prior pump had this issue. I don't know why such gross misalignment would have presented as a squeak getting gradually worse. Even stranger, I shimmed the pump back 1/4 inch, and found that the pulley hit the heads on the pump mounting bolts. So that means that the pulley can't sit as close to the PS pump mounting bracket as it needs to be in plane with the alternator and crank.
I shimmed the pump back as far as I could, and the system seemed to tolerate the slight misalignment without any noise, but I'm still not sure why I had to go through that.
The service manuals don't show any kind of spacer that I had inadvertently left out. The only clue I have is that the rebuilt pump I received had notes from ac/delco that it met all GM rebuild standards. So maybe GM uses a pump so similar that at some point it became incorrectly assumed to work with subarus?
Otherwise, I figured I'd check on the forums to see if someone else has come across this issue.
Heard a squeak which gradually got louder and more frequent
Eventually investigated to find a power steering pump leaking, alternator covered in serpentine belt debris.
Replaced power steering pump with rebuilt pump(ac delco) Squeak persisted and the rebuilt pump leaked.
I tore down both pumps to see what was wrong. Bearings were fine, no play, ran smooth. Pumping elements were fine. Return screen to the reservoir didn't have any debris in it.
Both leaking pumps were leaking out of the front seal, which is actually just a grease seal for the bearing. It seems that if the internal lip seal that separates the input shaft bearing cavity from the vane pump cavity leaks, the bearing cavity receives pressurized power steering fluid which makes its way through the bearing and out the input shaft. I'm guessing that even if the pump is rebuilt, and the replace the seal without repairing any wear on the sealing surface of the input shaft to the pump, that it will leak.
So I bought a new, aftermarket pump, not rebuilt. The leak was fixed, but the squeaking was still present, and as bad as ever. Ensured belt tension was good. The only way to reduce the squeak was to run the belt very tight, which I did not want to do.
Finally checked pulley alignment to find that the power steering pump was sitting a bit over 1/4" ahead of the crank and alternator pulleys. It ran true, but was just uniformly shifted. The mounting bracket wasn't loose and definitely doesn't have 1/4" of play, and based on the debris on the alternator from the 1st pump replacement, i'm guessing that the prior pump had this issue. I don't know why such gross misalignment would have presented as a squeak getting gradually worse. Even stranger, I shimmed the pump back 1/4 inch, and found that the pulley hit the heads on the pump mounting bolts. So that means that the pulley can't sit as close to the PS pump mounting bracket as it needs to be in plane with the alternator and crank.
I shimmed the pump back as far as I could, and the system seemed to tolerate the slight misalignment without any noise, but I'm still not sure why I had to go through that.
The service manuals don't show any kind of spacer that I had inadvertently left out. The only clue I have is that the rebuilt pump I received had notes from ac/delco that it met all GM rebuild standards. So maybe GM uses a pump so similar that at some point it became incorrectly assumed to work with subarus?
Otherwise, I figured I'd check on the forums to see if someone else has come across this issue.