PDWA Rebuild

[hondo402000]

any one know where to get the o rings for the PDWA? I see on Pauls site he says Moss but they dont list them. Got some O rings from Auto Zone but they are Viton and info I see says I need EPDM, Napa?

Hondo

 

[SkinnedKnuckles]

Viton should work with either DOT 4 or 5.

 

[JodyFKerr]

Just wrote up my rebuild: https://www.theymightberacing.com/Projects/InSitu/TS78/BrakesRefresh.aspx

The PDWA bits are ~2/3 of the way down the page.

I used Felpro ES 70599. (They're more commonly used as Fuel Injector O-rings). I also had a bugger of a time with the end cap until I used a Stat-O-Seal washer (rubber o-ring built in to the washer). I lost the munber, but they looked it up in the book at NAPA.

Jody

 

[glemon]

I got some from NAPA, I forget what they were made of (maybe Viton), not EPDM as recommended, but the huy assured me that it was fine with brake fluid, I let them soak awhile to see if any dissolve and was fine, they weren't cheap for little O-rings, seems like couple bucks a piece (I know that is not a lot of money, but not cheap for a tiny O-ring).

The rebuild was easy, followed the directions from a website, I think maybe Buckeye Triumphs.

 

[Brosky]

The Moss kit that I used is NLA? I wonder when they stopped supplying it? If you are sure, I'll post that on my site. Let me know.

 

[TR3driver]

Viton should work with either DOT 4 or 5.

Every source I checked said "not recommended". Eg,
https://www.efunda.com/glossary/design/oring/design--oring--chemical--automotive_brake_fluid.cfm

I'd keep looking for EPDM. If all else fails, MMC will sell you 100 of them for $4 or $5.

 

[SkinnedKnuckles]

Well - that's news to me. I usually look at several sources. Most don't have glycol butyl ethers listed. I really don't think Viton has any compatibility problems - but if there is some evidence I'd like to hear it.

Certainly not a problem with DOT 5.

 

[DougF]

I just bought the rebuild kit from Moss this past summer.

 

[TR3driver]

Well - that's news to me. I usually look at several sources. Most don't have glycol butyl ethers listed. I really don't think Viton has any compatibility problems - but if there is some evidence I'd like to hear it.

Certainly not a problem with DOT 5.

Here's a few more sources. Doesn't "prove" anything of course, since it's all on the Internet; but seems pretty persuasive to me.
https://www.pspglobal.com/fluid-compatibility/chemicals-d.html
https://www.marcorubber.com/materialguide.htm
https://www.dtechperformance.com/about_accessories.html
https://www.sealanddesign.com/category/2/Page/84/cpage/62/62.aspx
https://www.sealmech.com/o-ring.html

Also worth noting, perhaps, that the DOT standards for DOT 3, 4 and 5.1 do not specify the fluid composition at all; but do specify compatibility with EPDM. Since not all brake fluids are the same, it is possible that Viton (like the natural rubber seals originally used on TR2-4) is compatible with some glycol-based fluids but not all of them. This could apply even to DOT 5, since as I understand it, most DOT 5 fluids have "seal sweller" additives that may or may not be compatible.

But I'll freely admit that I'm very conservative when it comes to altering hydraulic brakes. If you want to experiment, go right ahead. Just please don't do it behind me.

 

[71MKIV]

www.mcmaster.com

Youse picks ur size and put it in the cart.

just search for epdm o rings.

 

[eschneider]

Moss 181-995? $12.95...

If I'm mis-reading the availability, I have a new kit on my bench I'd be happy to send ya for $10....

 

[hondo402000]

thanks all, NAPA had the o rings, 50 Cents each, position 8 in their o ring kit, used for hydrolics and I used the Part number for the switch on Pauls site C8AZ-2B264-A for 33 dollars. from Ford, I ordered it yesterday and it came in today

thanks again

Honco

 

[SkinnedKnuckles]

Also worth noting, perhaps, that the DOT standards for DOT 3, 4 and 5.1 do not specify the fluid composition at all; but do specify compatibility with EPDM. Since not all brake fluids are the same, it is possible that Viton (like the natural rubber seals originally used on TR2-4) is compatible with some glycol-based fluids but not all of them. This could apply even to DOT 5, since as I understand it, most DOT 5 fluids have "seal sweller" additives that may or may not be compatible.

But I'll freely admit that I'm very conservative when it comes to altering hydraulic brakes. If you want to experiment, go right ahead. Just please don't do it behind me.

Since DOT 3 at least used to be the most common fluid in use here, I think you may be on to something. One of the first things we hear as owners of British cars is NEVER use DOT 3 because of seal compatibility. Even with DOT 4 LMA fluid they won't last forever, though. Best thing I ever did was switch to DOT 5. No problems with my PDWA with viton o-rings (or anything else in the hydraulics) in 8 years.

 

[TR3driver]

One of the first things we hear as owners of British cars is NEVER use DOT 3 because of seal compatibility.

Not a matter of DOT 3 or DOT 4; I once verified that an American brand of DOT 4 would attack the seals; while Castrol did not (or at least not nearly as quickly). Until that experiment, I believed that all DOT 4 was the same, but clearly it was not.

But that was a long time ago, and I believe that all British seals manufactured in the past 20 years or so have been EPDM (and so compatible with any fluid).

 

[DNK]

$$33.00 bucks, wow pretty steep.

 

[dklawson]

Google C8AZ-2B264-A and you will find it is available for a bit less if you shop around. However, $33 is still much better than the price you will pay for a NOS Lucas one.

 

[DNK]

Tru Dat

 

[Brosky]

Good to know the seals are available from NAPA. Did they have the copper washer for the big bolt head on the end?

 

[hondo402000]

Paul I got a multi assorted pack of copper washers at auto zone and one of them fit, didnt ask napa but probably they would have had one, I alway use Castrol brake fluid and nothing else, Always keep a quart on hand and never had a problem.

Hondo