Rear proportioning valve (105) - Page 2

Rich · #16 (**permalink**) 06-22-2009, 06:01 AM

No problem Alex, will do.

**1750GT** · #17 (**permalink**) 06-22-2009, 07:00 AM

Any brake fluid found in the spring chamber portion of the valve indicates that the cup seal has failed. These seals should be replaced before re-assembly or (and this depends on the extent of the leakage) the valve may not function at all as intended. Ideally O rings should not be used to replace cup seals.

**Chris1750** · #18 (**permalink**) 06-24-2009, 05:14 AM

I talked to the guys at CBC today and unfortunately they didn't keep a record of the sizes or sources of the parts used to rebuild the PV. I didn't think that they would as it was such a small job, so many months ago.

What I'll do now is buy another one and pull it apart. I'll let you know how I get on.

Chris

Rich · #19 (**permalink**) 06-27-2009, 03:04 AM

Finally i had some time to pull it all apart, unfortunatelyI had rust and it is pitted, and found brake fluid in the chamber.
CBC Bearings at Kingsgrove (head office) had the O'rings but didn't have the correct cup seal.

Chris what state are you in?

O-ring size

26X2mm =$0.27
12X2.5mm = $0.12

I have sent the value to get it re-sleeved with stainless steel and they will supply the cup seal. I also asked for part numbers of all seals, should you guys want some.

Rich

**Chris1750** · #20 (**permalink**) 06-27-2009, 04:54 AM

Quote:

Originally Posted by Rich

Chris what state are you in?
Rich

**Chris1750** · #21 (**permalink**) 06-30-2009, 04:49 AM

The second hand PV arrived yesterday and I pulled it apart last night. It wasn't badly corroded at all, though it was covered internally in a sort of varnish. All of the seals were kaput and the cup seal split as I tried to carefully remove it. I've measured everything as below.

The O-rings were as Rich described and I haven't bothered with them any more as they are commonly available.

Dimensions marked on the piston are :

A - 12.00mm
B - 5.90mm
C - 12.65mm
D - inner 4.00mm, outer 4.50mm (there is a small 0.50mm step that is visible in the photo)

The cup seal has an outer diameter at the flared end of 13.00mm

For our USA subscribers, I'm sorry but this seems to be a metric component so all of the dimensions are in millimeters.

Now the hunt is on for the piston cup seal. I'll take this part up to the guys who helped me last year and see if they can recreate the magic.

Hope this helps,
Chris

Rich · #22 (**permalink**) 07-02-2009, 07:29 AM

Bad news, the guy from Marion Brakes & Clutch called me today to tell me they can't fix it, it's too pitted and the can't get the seals, *&^&%%$.

Chris, now that you have spare, do want to sell PV to me? Otherwise can you tell me from who you purchased it from?

Rich

**velocedoc** · #23 (**permalink**) 07-02-2009, 10:04 AM

What does the cup seal look like?

Lots of eyes on here can help source the part. Might come from another brake assembly. Send an inquiry to White Post Restorations. They do a lot of brake restoration work and might have a source for this part. I have read pro's and con's about White Post work, but that is for another thread.

**Anfanuts** · #24 (**permalink**) 07-02-2009, 11:25 AM

You can get them new from Alfaholics, perhaps elsewhere. I have no idea if the spring/pressure settings are the same. Where would find PV setting specs on the various years??

**Chris1750** · #25 (**permalink**) 07-02-2009, 06:20 PM

OK - I'll do my best here.

There are 3 photos below - one each of the top, side and underside of the cup seal.

The dimensions are as follows -

Top view: OD flared end 13.00mm, OD non-flared end 12.50mm, ID 5.50mm

Side view: Height at outer margin 3.20mm, height at inner margin 3.50mm, height of central part 3.90mm. Flared & non-flared end dimensions as above.

Underside: Thickness of seal rubber 1.20mm

On the underside, it is marked '13-H Ate' and '45386'.

Please bear in mind that even though my hand is steady, my eyes sharp and the digital verniers I use are of the best quality, this is an old split seal so there may be some minor variance in these measurements. (What's the old saying - a poor carpenter blames his tools

)

At present, I can't part with this one as it is about to be hawked around in order to find parts. Rich, try any of the secondhand Alfa parts dealers, though you may have to buy a couple before you get a good one. I think I got lucky with this one - and also with the seals a year ago, it seems.

Hope all of this helps,
Chris

**velocedoc** · #26 (**permalink**) 07-02-2009, 11:51 PM

That seal "almost" looks like a seal from a master cylinder kit, but on a much smaller scale. Thank you for taking the time to post the photos.

**Chris1750** · #27 (**permalink**) 07-03-2009, 12:01 AM

Quote:

Originally Posted by velocedoc

That seal "almost" looks like a seal from a master cylinder kit, but on a much smaller scale. Thank you for taking the time to post the photos.

Rich · #28 (**permalink**) 07-03-2009, 05:19 AM

I come, I see, I concrete!

Highwood sells them for 75 pounds new, I have decided to save myself the aggravation and buy a new one, the only thing though it is smaller in size and Chris said that i may need a longer pipe line, which isn't a problem because i made all new brake lines myself and re-chromed all the fittings.

Thanks for your help Chris1750

damoj · #29 (**permalink**) 07-03-2009, 01:31 PM

I am rebuilding one of these too. I have talked to a local shop and they gave me a seal to try. I have already sourced the 2 O-rings local. I should have it put back together today and see how it works.

**Anfanuts** · #30 (**permalink**) 07-03-2009, 04:27 PM

Quote:

Originally Posted by Chris1750

I keep wondering why this thread has generated such interest. Am I the first person to have dismantled one of these valves?

Chris