PDWA Internal Arrangement

Dick,
This is great! Thank you for sending this and I will be ordering one this week!

Dick;
Off topic, but how is the rotisserie and rebuild going?

Regards, Joelā€¦

Dick,
I finally got out in the shop today and worked on my PDWA. I was able to get the end caps off and re-center the spool eliminating the light! It was pretty easy to move the spool but took a little fiddling to get it centered. THere was no corrosion present and even though one side of the sppol leaked, the fluid was clean and no black rubber residue. I will try to replace the seals net time I have to break into the hydraulic system. I did not have the small spring in the switch cavity and my light worked fine. I am not really sure how it works so did not reconstruct one.

Again, thanks for the excellent pictures and help! Now on to the pesky reaction valve!

Doug,
If youā€™re replacing the PDWA seals make sure you source AS568-009 SQUARE O-ring seals.made from EPDM. EPDM is the only material suitable for brake fluid application. Caution against using round O-rings---- Donā€™t!!! Iā€™ve been trying to source EPDM Squre O-rings but only found them readily available from DavidManners in the UK. I did find one US firm that quoted $6 per seal with a 9 week delivery time. Outrageous! Girling long ago make a rebuild kit SP2615 but itā€™s been NLA for about 9 years. Sounds like your valve is better off than some Iā€™ve seen. Thatā€™s goodā€¦ Less workā€¦ Ha Ha
Good luck,

Dick

I did a Google search using the above quoted data and found a bunch of AS568 O-Rings offered by

I found some square ones but I donā€™t know enough to pick out the EPDM stuff

Are any of these made of the right stuff?
What size O-Ring is required?

At the top of the McMaster-Carr link you sent, it shows the ones they offer are made of Buna-N, not EPDM. Iā€™m ignorant of what o-ring materials are compatible with different fluids/applications, but a quick Google search reinforced Dickā€™s recommendation: EPDM is what you want for brake system applications.

Do you believe in Dog?

:grimacing:

Dyslectics of the World ā€“ UNTIE

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Bob ā€“ I saw that but admit complete ignorance regarding what Buna-N is, what EPDM is, and whether or not if they are the same thing with different names.
ā€œA Rose by any other Name is Still a Roseā€ sorta thing

Buna-N and Nitrile are different names for the same thing.
See this chart.

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One of the favorite t-shirts I own -

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So I am finally getting around to rebuilding my PDWA properly. It started leaking through the connector so the internal seals finally died. As everyone has found, finding the EPDM square seals is next to impossible so I order some from David Manners In the UK. They arrived amazingly fast and I have now removed the PDWA to clean and rebuild it.

The small ball to actuate the switch was missing so I got a 1/8ā€ ball bearing that works well at the local Ace. Also missing was the spring that Dick showed in my initial post. Can anyone describe the purpose of that spring so I can understand how to make and install it? The switch plunger is spring loaded and long enough so I canā€™t see the spring holding the ball in place. Any insight is appreciated!

Doug

Just to say many thanks to Dick for a very clear explanation of the PDWA, which gave me the knowledge to take mine apart.

I found it in servicable condition inside and now know that the funny little ball point spring did not bend as I took it out and the PDWA can be reused saving me Ā£150 but assuming I can find some new seals.

Cheers
Bob