Help to fully understand hydraulic PAS and track an air leak
Discussion
I have a b5 A4 (2.8 30v) which is a track project… After the last track outing the PAS pump was making a horrendous rattle, so I swapped that out for a second hand pump. That didn’t change anything, and on further investigation the rack was leaking at one end, so that was also swapped out for a used one. Which seemed to fix the problem!
Not long after I drove the car out the yard to load on a trailer, at which point PAS was working fine. However the car had no front bumper on it, the cooler which runs around the front was not secured, and the cooler ripped off dragging under the car.
I have replaced the cooler however I now cannot bleed the system. Even without the engine running there’s a lot of air coming up through the reservoir when I turn the wheel left to right, no matter how many times I do it. I’ve tried a different cooler, I’ve even completely bypassed the cooler plumbing the return line straight into the reservoir. I’ve also checked the feed to the pump from the reservoir (seems an obvious place to be sucking in air) and all seems fine, not that it was ever disturbed.
Now, because it’s letting air in and not leaking fluid it’s making it very difficult to track down. I suspected the return line might have been snagged as I ripped the cooler off, however surely a return line wouldn’t be sucking in air?
So if someone could help me understand points in the system that might be sucking in air, that would be a great help!
TIA
Not long after I drove the car out the yard to load on a trailer, at which point PAS was working fine. However the car had no front bumper on it, the cooler which runs around the front was not secured, and the cooler ripped off dragging under the car.
I have replaced the cooler however I now cannot bleed the system. Even without the engine running there’s a lot of air coming up through the reservoir when I turn the wheel left to right, no matter how many times I do it. I’ve tried a different cooler, I’ve even completely bypassed the cooler plumbing the return line straight into the reservoir. I’ve also checked the feed to the pump from the reservoir (seems an obvious place to be sucking in air) and all seems fine, not that it was ever disturbed.
Now, because it’s letting air in and not leaking fluid it’s making it very difficult to track down. I suspected the return line might have been snagged as I ripped the cooler off, however surely a return line wouldn’t be sucking in air?
So if someone could help me understand points in the system that might be sucking in air, that would be a great help!
TIA
Can someone please help me hone in on where air might be getting in the system...
I had a closer look at the return hose, and sure enough it was leaking a little. I've replaced it for a better one and still no joy... I still can't even get the system to bleed without the engine running, no matter how many times I go all the way left and right there's still bubbles getting into the reservoir.
Begs the question whether the rack is any good, but surely if it was the rack I'd be leaking fluid from there as well??????????
Short of replacing absolutely everything in the system one by one I'm really running out of ideas.
The car is due on track two weeks today and I've already paid for my ticket. If I can't get to the bottom of this by the end of next weekend I'm gonna have to throw the towel in :'(
I had a closer look at the return hose, and sure enough it was leaking a little. I've replaced it for a better one and still no joy... I still can't even get the system to bleed without the engine running, no matter how many times I go all the way left and right there's still bubbles getting into the reservoir.
Begs the question whether the rack is any good, but surely if it was the rack I'd be leaking fluid from there as well??????????
Short of replacing absolutely everything in the system one by one I'm really running out of ideas.
The car is due on track two weeks today and I've already paid for my ticket. If I can't get to the bottom of this by the end of next weekend I'm gonna have to throw the towel in :'(
Thank you, exactly the sort of answer I was looking for...
So just to clarify, "low pressure side" is the return from the rack to the reservoir, could that also include the feed to the pump from the reservoir? . . And anything else would be pressurised and therefore should show signs of leaking?
Do you think it would also safe to rule out the pump it's self from the symptoms shown?
So just to clarify, "low pressure side" is the return from the rack to the reservoir, could that also include the feed to the pump from the reservoir? . . And anything else would be pressurised and therefore should show signs of leaking?
Do you think it would also safe to rule out the pump it's self from the symptoms shown?
The last time it was working properly was after I fit the last rack and just before I accidentally ripped off the cooler...
If I try with the engine running at the moment I might get some sort of intermittent assistance through the wheel and the pump will make an awful noise... Just as you'd expect from a system with air in it
If I try with the engine running at the moment I might get some sort of intermittent assistance through the wheel and the pump will make an awful noise... Just as you'd expect from a system with air in it
VAGslag said:
So just to clarify, "low pressure side" is the return from the rack to the reservoir, could that also include the feed to the pump from the reservoir? . . And anything else would be pressurised and therefore should show signs of leaking?
Exactly.VAGslag said:
Do you think it would also safe to rule out the pump it's self from the symptoms shown?
I wouldn't rule it out completely since a failed seal might allow air in, but you already know there was an external leak previously and it would be an odd coincidence to have two different failures with identical symptoms at the same time.Gassing Station | Home Mechanics | Top of Page | What's New | My Stuff