Hydraulic fluid renewal and pressure relief

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Hydraulic fluid renewal and pressure relief

Post by BXTASY » Sat Aug 12, 2017 3:47 pm

Bxers - On my ’88 GTI, I’ve removed the hydraulic reservoir for cleaning and painting, and will renew the LHM. If any air gets into the lines, is this a problem? Or will it be eliminated through several cycles of height adjustment?

A step-by-step procedure for renewing the fluid and cycling the system would be helpful. A couple of the drain lines from the rear cylinders are disconnected, now I’m unsure of the reattachment points at the reservoir. Does anyone have a good closeup photo of the octopus and all lines?

On the accumulator/junction block, where is the pressure relief screw? I cleaned and painted the whole assembly, but could not identify this.

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Re: Hydraulic fluid renewal and pressure relief

Post by RobC » Mon Aug 14, 2017 11:24 am

Air will work its way out as lon as you remember to bleed all the brakes afterwards- they're the only dead ends.

I don't think it matters too much which return lines go back where- stand to be corrected on this mind you - but in the past I've got away with it with seemingly no ill effects.

Bleed screw is the only 12mm bolt on the pressure regulator. no need to unscrew it completely!
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Re: Hydraulic fluid renewal and pressure relief

Post by Defender110 » Mon Aug 14, 2017 12:27 pm

The pressure release screw is also used to prime/bleed the system after you have changed the oil. Once the system is primed and the LHM is flowing any other air trapped in the suspension/steering will make it's own way out of the system as it flows round.
If you wish to change the LHM in the brake lines you will need to bleed each brake individually at the hubs.
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Dragon Man
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Re: Hydraulic fluid renewal and pressure relief

Post by Dragon Man » Fri Aug 18, 2017 10:10 am

for me it was simple, to release the pressure in the system i just put the car to the lowest position then kept pumping the brake pedal. even though the car was already low with every pump i was able to make the car sink lower until the brake pedal did not do the "hiss" sound while taking the pressure i held down off the pedal.

filling and priming the system was a little more difficult, but when you forget to screw on the accumulator sphere... yeah it kinda primes rather quick.. :/
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