6 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH996 PAS pump loud noise, sucking air.....
Reported or suspected cause
cavitation
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
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Reported cause
The froth is caused by cavitation which was caused because the return pipe from the rack had come off in the header tank of th ps unit.
Leading evidence: 'cavitation' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'cavitation' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Fill pump' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
A pump that's run dry for any sensible amount of time and again this is the noise you will get but it will need a new pump in this case ..
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Suggestion
air enters the system and the pump is noisy because of this or the pump has been previously run dry and is damaged .
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
911uk: 1 discussions
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Hi There
Having just started our 996.2 after a complete engine rebuild we have found that the PAS pump is making a hell of a noise. Its foaming the fluid and sounds like it is rattling and sucking air furiously. With the serpentine off if you turn it back and back and forth it makes a clonking/rattle and there is play on the transition as you rotate it back and forth.
The state of the pump was unknown pre rebuild as the car was bought with a non running engine.
Here is a youtube of the noise.......
https://youtu.be/Mjr7ZEWwIxM
Any guidance appreciated!
Many thanks
Berni
Pas noises are caused by a leak or a faulty pump .. air enters the system and the pump is noisy because of this or the pump has been previously run dry and is damaged .
Engine out / replace .. fill the pump .. run the car and steering wheel lock to lock .. top up pas fluid .. if still noisy then look in the bottle .. is it air rated .. lots of bubbles .. if so a leak or air entering the system somehow .. if not then a pump replacement might be on the cards if it doesn't go quiet after 10 mins .
Pas noisy .. pump usually works fine .. it's just noisy .
Hello De Mort
Thank you for that. We were looking at some Porsche PAS pump videos and we found one where the pump was exhibiting the same play when rotated. The guy stripped it and it turns out to have been play in the impeller splines.
We are then thinking that because we did not turn the steering lock to lock more than a couple of times after refitting the engine it might not have been enough to bleed the air out, and the cavitation caused by the foamy fluid may be causing the pump to chatter on the worn splines.
So tomorrow we will investigate again properly.
Thanks again
Berni
Hi
Just to close off this thread, after some mucking about we cleared the system of air and all seems well now. I had read that low of frothy fluid causes a whine, but be advised it can also cause a very loud noise as described above also.
Thanks
Berni
I had something similar on my volvo.
The froth is caused by cavitation which was caused because the return pipe from the rack had come off in the header tank of th ps unit.
The return pipe returns the fluid under the level of the tank so no air actually gets into the send side of the pump.
What was happening was the retuned fluid was like a water spout splashing on top of the resovoir and air bubbles formed and were sucked into the system and returned as foam.
I fished the pipe out from the resovoir and reconnnected it and all was well.
As DeMort said it could be an air leak somewhere.
After an engine drop the pas needs refilling and bleeding basically .. the air bubbles as mentioned cause the pump noise ..
You turn the steering lock to lock a few times , refill and it self bleeds ..
A leak and as fluid leaks out air will also enter causing the same noise .
A pump that's run dry for any sensible amount of time and again this is the noise you will get but it will need a new pump in this case .. it's pretty loud isn't it
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