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Old 05-29-2018, 05:32 PM
Registered User
Join Date: May 2018
Location: Big Island Hawaii
Posts: 12
87 300D 603 PS pump pressure output & upgrade

Hopefully this is the correct forum to post this question. :-)

What is the PS output pressure on a 87 300D 603? I need 105bar/1500psi or higher to run the PS and hydro brakes.

I think the w124 PS pump puts out 90-95bar? If so can the pump be modified or upgraded to 115bar that later ones put out, or will I need to get a different pump?

If I need to get different pump, is there one that would be a direct bolt on to the 603? If so, what one do I need to use?

Cheers, Allen

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Old 05-29-2018, 06:25 PM
scottmcphee's Avatar
1987 w124 300D
Join Date: Mar 2008
Location: Edmonton, Canada
Posts: 1,539
Why do you need more pressure than the power steering pump is designed to deliver to run the car's steering system?

Brakes don't run off that same pump. They're vacuum boost hydraulic. There's a vacuum pump on the engine to create the vacuum needed for brake boost. Vac is usually measured in inches of mercury pull up a column.

There's also a diesel injector pump that produces 135bar to pop the injectors to put fuel into the cylinders.

Maybe you're confused about the duality of PS fluid? The automatic transmission uses the same fluid as power steering but they're two different systems.
Scott McPhee

1987 300D
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Old 05-29-2018, 11:26 PM
Registered User
Join Date: Oct 2013
Location: New Zealand
Posts: 498
Lol. OP forgot to mention he's swapping the engine into another chassis.
Hydroboost brakes use the pressure from the PS pump as an assist rather than vacuum.
I only know about the W123 pumps not 124s.

Pressure of course is set by the relief valve so you could screw it in a bit, but then you risk blowing out a seal or something but I think you'd be fine...

1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...not yet legal
1984 240TD>300TD 121,000 miles, *sold*
1977 250 parts car
1977 280> 300D - 500,000km+
1981 200>240D
1975 FJ45>HJ45

1999 Hyundai Lantra 1.6

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