 Brake proportioning valve. |
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| 914Toy |
 Dec 7 2019, 03:11 PM
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Senior Member  Group: Members Posts: 717 Joined: 12-November 17 From: Laguna beach Member No.: 21,596 Region Association: Southern California 
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Like most of our cars, the brake proportioning valve is 45 to 50 years old. While it's design and action is relatively simple, - holds the hydraulic pressure at a factory determined maximum value (550lb/square inch?) while under pedal pressure, the probabilities of function failure must exist - whether through wear or contamination.
In my case, my brakes work well and when bleeding them all four calipers appear to experience free flowing brake fluid. My proportioning valve does not leak and there are no signs of abuse, or that it has ever been "serviced", but the latter is hard to tell. My guess is it still works or is "seized" and works as a simple T connection for the three brake lines. I have refurbished stock rear brakes and have just installed Boxter front calipers on 911 Carrera suspension. Brakes are much improved and I can't get the rear brakes to slide under hard braking, suggesting the more effective front brakes "overpower" the rear brakes such that a proportioning valve is no longer necessary. Any comments will be welcome. |
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| 914_7T3 |
Dec 7 2019, 03:25 PM
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Please forgive me, I'm new to all of this! Group: Members Posts: 1,847 Joined: 3-April 17 From: Los Angeles, CA Member No.: 20,991 Region Association: Southern California
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I bet @Eric_Shea could answer that question.
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| 76-914 |
Dec 7 2019, 03:32 PM
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,494 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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Keith, if it turns out you need the proportioning valve pm me. I have a few sitting around. (IMG:style_emoticons/default/beerchug.gif)
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| Superhawk996 |
Dec 7 2019, 04:58 PM
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#4
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914 Guru Group: Members Posts: 5,778 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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QUOTE(914Toy @ Dec 7 2019, 04:11 PM)  Brakes are much improved and I can't get the rear brakes to slide under hard braking, suggesting the more effective front brakes "overpower" the rear brakes such that a proportioning valve is no longer necessary. Any comments will be welcome. This suggests the proportioning valve is working. You still need a rear proportioning valve. If you were getting full pressure to the rear (without a proportioning valve) you would get rear wheel lock and especially so on wet pavement, snow, or ice. You never want rear wheels to lock 1st. It makes the vehicle inherently unstable. I highly recommend Eric's services. You want and need a functional proportioning valve. His price is incredibly resonable and ensures that the 40-50 year valve is working properly. |
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| rgalla9146 |
Dec 7 2019, 07:11 PM
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Advanced Member Group: Members Posts: 4,545 Joined: 23-November 05 From: Paramus NJ Member No.: 5,176 Region Association: None
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Watch your terminology.
It's known as a 'brake pressure regulator' I was recently corrected by Mr. Shea himself. |
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| Cairo94507 |
Dec 7 2019, 07:26 PM
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Michael Group: Members Posts: 9,731 Joined: 1-November 08 From: Auburn, CA Member No.: 9,712 Region Association: Northern California
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PMB rebuilt mine and it came back looking like new of course. (IMG:style_emoticons/default/beerchug.gif)
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| 914Toy |
Dec 8 2019, 09:49 AM
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#7
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Senior Member Group: Members Posts: 717 Joined: 12-November 17 From: Laguna beach Member No.: 21,596 Region Association: Southern California
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Thanks for your responses. After more testing will post again.
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| Superhawk996 |
Dec 8 2019, 10:14 AM
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#8
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914 Guru Group: Members Posts: 5,778 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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QUOTE(rgalla9146 @ Dec 7 2019, 08:11 PM) Watch your terminology. It's known as a 'brake pressure regulator' I was recently corrected by Mr. Shea himself. (IMG:style_emoticons/default/bootyshake.gif) (IMG:style_emoticons/default/laugh.gif) Don't disagree. You are correct. It is the equivalent of everyone calling anti-roll bars -- sway bars. I certainly don't way sway! (IMG:style_emoticons/default/av-943.gif) |
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| Jett |
Dec 8 2019, 10:18 AM
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Senior Member Group: Members Posts: 1,637 Joined: 27-July 14 From: Seattle Member No.: 17,686 Region Association: Pacific Northwest
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All three of our 914’s have full PMB restored braking systems and new master cylinders (IMG:style_emoticons/default/smile.gif) The only problem is that they look so good it forces us to powder-coat the backing plates and plate the hardware (IMG:style_emoticons/default/smile.gif)
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