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914World.com _ 914World Garage _ got the brake issue fixed

Posted by: Type 47 Jan 2 2023, 06:50 PM

We had issues with the rear brakes not bleeding and isolated it to the pressure regulator, so went out and pulled a backup off the parts cars.

the swap fixed the issue and brakes are bled.

So we decided to take apart the bad one. Here is what is looks like a part. Those o rings were pretty gummed up preventing the piston from moving.

Posted by: Chaznaster Jan 2 2023, 07:43 PM

I always wondered what one of those looked like inside. Thanks for sharing ... Are they rebuildable or is that dangerous (because brakes ...).

Posted by: mb911 Jan 2 2023, 07:53 PM

QUOTE(Chaznaster @ Jan 2 2023, 05:43 PM)

I always wondered what one of those looked like inside. Thanks for sharing ... Are they rebuildable or is that dangerous (because brakes ...).

Rebuildable. PMB offers the service or just the kit

Posted by: zoomCat Jan 2 2023, 07:55 PM

QUOTE(Chaznaster @ Jan 2 2023, 08:43 PM)

I always wondered what one of those looked like inside. Thanks for sharing ... Are they rebuildable or is that dangerous (because brakes ...).

Rebuilding looks easy, but how do you calibrate? Do you need to?

https://pmbperformance.com/products/pressure-regulator-repair-kit?_pos=1&_sid=31997779c&_ss=r

Posted by: Superhawk996 Jan 2 2023, 08:09 PM

QUOTE(zoomCat @ Jan 2 2023, 08:55 PM)

Rebuilding looks easy, but how do you calibrate? Do you need to?

Yes they need to be recalibrated. You do not want a car with too much rear brake bias. Rear brake lock is inherently unstable, and dangerous both to you and others that share the road with you.

The curve is in the factory manual. The reality is most folks don’t have the appropriate high pressure gauge(s) or the bench rig to supply the pressure to set it.

If simply taken apart and reassembled without changing the adjustment screw, it will be close.

Send to PMB for a full restoration is the way to go.

Posted by: Mikey914 Jan 4 2023, 10:52 AM

Just curious, how is it adjustable? Seems like the bias is set by the spring? popcorn[1].gif

Posted by: zoomCat Jan 4 2023, 12:10 PM

QUOTE(Mikey914 @ Jan 4 2023, 12:52 PM)

Just curious, how is it adjustable? Seems like the bias is set by the spring? popcorn[1].gif

You set the preload on the spring.

Group_6_Brakes___pressure_regulator.pdf ( 97.34k ) Number of downloads: 37

Oops, almost forgot this one.

Group_6_Brakes_pressure_regulator_2.pdf ( 186.95k ) Number of downloads: 44

Posted by: Type 47 Jan 4 2023, 05:27 PM

QUOTE(zoomCat @ Jan 4 2023, 10:10 AM)

QUOTE(Mikey914 @ Jan 4 2023, 12:52 PM)

Just curious, how is it adjustable? Seems like the bias is set by the spring? popcorn[1].gif

You set the preload on the spring.

Group_6_Brakes___pressure_regulator.pdf ( 97.34k ) Number of downloads: 37

Oops, almost forgot this one.

Group_6_Brakes_pressure_regulator_2.pdf ( 186.95k ) Number of downloads: 44

so if you just took it apart and put new seals on it do you have to set the preload again?

Posted by: NARP74 Jan 4 2023, 05:54 PM

Theoretically no if you did not touch the spring adjustment. But then again that is a 50 year old spring, not sure it is as good as new. I think I would get it calibrated again.