Printable Version of Topic

Posted by: 914Toy Dec 7 2019, 03:11 PM

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.

Posted by: 914_7T3 Dec 7 2019, 03:25 PM

I bet @http://www.914world.com/bbs2/index.php?showuser=1110 could answer that question.

Posted by: 76-914 Dec 7 2019, 03:32 PM

Keith, if it turns out you need the proportioning valve pm me. I have a few sitting around.

Posted by: Superhawk996 Dec 7 2019, 04:58 PM

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.

Posted by: rgalla9146 Dec 7 2019, 07:11 PM

Watch your terminology.
It's known as a 'brake pressure regulator'
I was recently corrected by Mr. Shea himself.

Posted by: Cairo94507 Dec 7 2019, 07:26 PM

PMB rebuilt mine and it came back looking like new of course.

Posted by: 914Toy Dec 8 2019, 09:49 AM

Thanks for your responses. After more testing will post again.

Posted by: Superhawk996 Dec 8 2019, 10:14 AM

Don't disagree. You are correct. It is the equivalent of everyone calling anti-roll bars -- sway bars. I certainly don't way sway!

Posted by: Jett Dec 8 2019, 10:18 AM

All three of our 914’s have full PMB restored braking systems and new master cylinders The only problem is that they look so good it forces us to powder-coat the backing plates and plate the hardware


Attached image(s)