W211 Power steering pump hydraulic fitting size

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by selphy, Jul 14, 2018.

  1. selphy

    selphy Active Member

    Mar 10, 2013
    Mercedes E220CDi
    Bit of a long shot but here goes...

    I'm troubleshooting heavy steering on a 2008 W211 and I have reached the point where I need to test the pressure output of the pump which I understand should be between 120 and 128bar at 1000rpm. I don't want to waste money on a new pump before testing the old one and I've exhausted all other troubleshooting.

    I obtained a second hand 0-140 bar hydraulic test gauge for power steering systems with an isolation valve. Unfortunately the fittings on the hoses don't fit and none of the adapters in the kit do either.

    I need to insert the gauge inline between the power steering pump outlet and the hydraulic pressure hose which runs to the rack. I will need to buy an adaptor or get a hose made up but I am not certain about the fitting type on the pump outlet. I measured the outer diameter of the male thread of the hose fitting in the pump as 15.8mm. Researching the various fittings I now think I need a 5/8 inch male fitting according to standard SAE J512 which has a 45 degree flare seat. However, it seems that the a more common standard for automotive power steering applications is SAE J514 (also known as JIC) which has a 37 degree flare seat. According to the thread charts JIC is available as either 9/16 (too small) or 3/4 (too big).

    Before I damage the female threads in my power steering pump with the wrong fitting I thought I'd ask the question in case anyone has been through this before. Like I said, it's a long shot...

    Thank you
  2. Azeem

    Azeem Hardcore MB Enthusiast

    Feb 1, 2016
    W211 E270 cdi - 2003
    Hi, I may not be able to help you with your query but I am having the same issue as yours. I have flushed the PS system once with new oil and read somewhere that there may be air in the system and to do a proper flush air has to be taken out. If I flush the fluid from power steering rack would it flush the system properly?

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