PS Fluid overflowing out of the reservoir cap
Thread Starter
Junior Member
Joined: Dec 2011
Posts: 40
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05 E55 AMG
PS Fluid overflowing out of the reservoir cap
Hello everyone,
I recently bought an 05 E55 that seemed to have a small power steering leak. The pump was whining, fluid was bubbly, i could hear the pump cavitating and fluid was leaking out of the reservoir cap. With the cap open and the engine on the fluid was FOAMING. I thought there was air in the system.
I replaced the reservoir and the reservoir seal with OEM parts, bled the system with wheels up in the air till the bubbles stopped coming out. After the process was done, everything seemed fine. The power steering pump was perfectly quiet with no whining or groaning at all. Which makes me think my pump is still good. I checked the fluid level and filled it up to the proper level at 80C.
After another drive a couple of hours later I started to hear the dreaded PS pump whine and look under the hood and see power steering fluid has leaked out of the cap again. Any ideas on what it could be?
Thanks in advance.
I recently bought an 05 E55 that seemed to have a small power steering leak. The pump was whining, fluid was bubbly, i could hear the pump cavitating and fluid was leaking out of the reservoir cap. With the cap open and the engine on the fluid was FOAMING. I thought there was air in the system.
I replaced the reservoir and the reservoir seal with OEM parts, bled the system with wheels up in the air till the bubbles stopped coming out. After the process was done, everything seemed fine. The power steering pump was perfectly quiet with no whining or groaning at all. Which makes me think my pump is still good. I checked the fluid level and filled it up to the proper level at 80C.
After another drive a couple of hours later I started to hear the dreaded PS pump whine and look under the hood and see power steering fluid has leaked out of the cap again. Any ideas on what it could be?
Thanks in advance.
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Joined: Jan 2014
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From: Republic of Texas
'99 and '05 E55 AMG
I had situation like this once. Turned out to be a bad bearing in the power steering pump that was heating up and literally causing the hydraulic fluid to boil. Put an IR thermometer on the pump and/or fluid and check the temperatures.
Alternatively, pressure valve is stuck and the fluid is again heating up from being churned by the pump because the fluid is not circulating through the steering rack. Less likely scenario since you wrote that could bleed the system.
Alternatively, pressure valve is stuck and the fluid is again heating up from being churned by the pump because the fluid is not circulating through the steering rack. Less likely scenario since you wrote that could bleed the system.
Thread Starter
Junior Member
Joined: Dec 2011
Posts: 40
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05 E55 AMG
Thanks bbirdwell!
I'll check the temperature and report back. The pump running super smooth and quiet after the initial bleeding procedure makes me believe the pump is still ok. I'll bleed it again and see what happens.
I'll check the temperature and report back. The pump running super smooth and quiet after the initial bleeding procedure makes me believe the pump is still ok. I'll bleed it again and see what happens.
Thread Starter
Junior Member
Joined: Dec 2011
Posts: 40
Likes: 1
05 E55 AMG
Well,
Seems like I definitely have air getting into the system instead of an boiling issue. Bled the system again, went for a drive - car and pump was quiet and smooth. Parked up for the night and it started FOAMING out of the cap again on a cold start and the pump started whining a couple of seconds later.
Will be visiting my mechanic to check for leaks. Hoping it's the pump or a line instead of the rack, area around the rack does seem pretty dry.
Seems like I definitely have air getting into the system instead of an boiling issue. Bled the system again, went for a drive - car and pump was quiet and smooth. Parked up for the night and it started FOAMING out of the cap again on a cold start and the pump started whining a couple of seconds later.
Will be visiting my mechanic to check for leaks. Hoping it's the pump or a line instead of the rack, area around the rack does seem pretty dry.
Thread Starter
Junior Member
Joined: Dec 2011
Posts: 40
Likes: 1
05 E55 AMG
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