HPF problem - Mercedes-Benz Forum
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post #1 of 27 (permalink) Old 11-07-2018, 12:22 PM Thread Starter
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Question HPF problem

Hi people,
I have a 1990 Euro 560SEL with full hydro suspension on four corners. Gen II full HPF factory settings are automatically lowering the the car by about one inch and the suspension gets stiff for better road handling when the carís speed exceeds about 120 Kmh / 70 Mph. Great feature for a car at that time yet the problem is the car is not raising again after slowing down below that trigger speed. Iím not sure if the system is set up like that or mine have a problem with raising back up to normal ride height for some reason. I need some expertise please. Thanks...
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post #2 of 27 (permalink) Old 11-07-2018, 06:18 PM
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Omer,

how can you tell, that it doesnīt come up again? If it still lowers the car everytime you reach 120 km/h - when does it raise again? Only after a restart?

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post #3 of 27 (permalink) Old 11-07-2018, 10:53 PM Thread Starter
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Thatís what I donít know Roland. If there is a speed sensor triggering the lowering process same should go for raising Iím thinking. Otherwise yes it raises back up after a restart and stiffness also goes away to comfortable softness in suspension . I believe this process also should be automatic. Iím not sure though. Thanks.
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post #4 of 27 (permalink) Old 11-08-2018, 01:34 AM
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@KRH , maybe you can help too?

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post #5 of 27 (permalink) Old 11-08-2018, 01:19 PM Thread Starter
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@KRH , maybe you can help too?
Hi KRH, I would be pleased to hear from you regarding your expertise on the HPF system of these great cars.
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post #6 of 27 (permalink) Old 11-19-2018, 01:23 PM Thread Starter
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Hi guys, any other ideas please ?
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post #7 of 27 (permalink) Old 11-20-2018, 11:59 AM
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Assuming it is similar system to the W116 6.9, The nitrogen spheres only last about 10 years, so new one all around if needed.

The pump itself could be worn. a oring rebuild is only needed if leaking, but wont repair a worn one.

I dont know what component triggers the lower and raising, but perhaps it needs rebuilt.

These guys will have the answer

600AirSuspension
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post #8 of 27 (permalink) Old 11-20-2018, 12:28 PM Thread Starter
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Hi Rumb, thank you for the help. Nitro balls are fine. The pump has been changed with a NOS one yet all in all itís not a fresh out of factory part, so I donít know. The problem is not only raising the ride height back to normal after slowing down below 120 km/h (70 mph) also after a while from engine start the HPF warning lamp comes on and stays on as long as the engine rev is at idle. That might be the root cause. Thanks for the link though. I checked the web site and impressed with expertise and also the prices. I will consult them. I hope they donít charge for consulting though 😊. Cheers.
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post #9 of 27 (permalink) Old 11-20-2018, 12:54 PM
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The block on top of the hydro tank controls the outputs. That might need cleaning. There are about 3 tiny ball bearings in there that act as valves. If the 5th sphere doesn't detect enough preasure the valve block won't send fluid to the struts and the light will be on. There is a pressure switch on top of the 5th sphere.
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post #10 of 27 (permalink) Old 11-21-2018, 12:34 PM Thread Starter
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Dear Rumb, the hydro tank , the valve ( pressure regulator) that goes in it and the block on top of it ( ride height control valve ) all NOS , again not fresh parts yet new and recently changed. As for the fifth sphere, good idea and I didnít know the function of the fifth one, I will look into it. The warning lamp for HPF comes on after the engine and other systems and fluids along with it ( incl. hydro ) gets warm enough after a while. So do you think that is related to the problem and also to the fifth sphere.? And what do you think about automatic ride height adjustment with speed? Is it lowering only or should there be an automatic raising back up to normal. That ride height setting also stiffens and softens the suspension. Thanks.
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