Im rebuilding all the brakes on my 280Z and now I am at the NP-valve (Proportioning valve) and the Brake indicator switch. The parts are ok, but I would like to replace all the seals.

The NP-Valve is still availible at Nissan under P/N: 46400-P9200 but it cost $325,00. The Brake fail indicator switch is also only available as a complete unit. Internals are NLA. All I want are the internal seals and o-rings.

Does anybody know where you can get the kits these days?

Appreciate any help.

I would go to a parts store and match up the o-rings. The parts here locally have trays of o-rings for 'free-style' fitting. I am pretty certain it will be that way where you are too. It might be tricky to find the little one on the little plunger inside the housing. I think it is great you went the extra step to actually remove and repair the Proportioning Valve - most people ignore it. I am glad that you posted pics too, that will be good for the future. Let us know the outcome!

I would be careful on material with the o-ring. Plain old plumbing o-rings might absorb brake fluid and swell (I tested an Ace Hardware o-ring to see if it could be used - it swelled). Viton would be fine if you can find them. I don't know what the typical material used is, and most manufacturers that I've seen don't list it. It's a problem.

Most of the off the shelf O-rings you will find in the hardware store are Neoprene, or Buna-N (Nitrile). And I'm not so sure that I would jump on the Viton bandwagon so quickly... Viton (fluorocarbon) is not compatible with glycol based brake fluids. I have no idea what today's brake fluids are made from, but the incompatibility bore special mention in the application charts.

Point I'm trying to make is do your research homework first. :bulb:

Hi guys, Thanks for the input. Greatly appreciated.

I agree, the O-Rings are easy to replace. When I find the sizes, I will post then.

Most brake components are EPDM, but Im not sure if its sulpher cured or peroxide cured.

Where I work we use a lot of O-Rings and gaskets and our experience with the peroxide variant is better in higher temperature conditions.

This company is good for information about rubber compounds. A link to there site Datasheets | O-Ringen They recommend there 559311 compound which is peroxide cured EPDM.

My biggest challenge is to find replacement cups. Its difficult to know where to start. I was thinking of trying a brake specialist and looking at what he has that might fit.

My goal is to retain the original proportioning valve and not replace then with some aftermarket unit. Trying to keep a bit of original look in the car.

Ill keep you posted.

Chas

Hi Zcurves,

Your idea is just what I had in plan. Take to parts to a hydraulic shop and find which o-rings fit best. Then order then in EPDM.

Chas

Found the size of the two o-rings today. The two behing the nuts.

Size 16.39x2.21mm (IDxCross section) according to standard AS568-908. The cups are going to be harder to solve if at all.

  Captain Obvious said:

not so sure that I would jump on the Viton bandwagon so quickly... Viton (fluorocarbon) is not compatible with glycol based brake fluids. I have no idea what today's brake fluids are made from, but the incompatibility bore special mention in the application charts.

You got me. I made an assumption (that all fluoropolymers would be fine with brake fluid), and a bad suggestion. I should know better.

Sounds like Eurodat has the best resource for figuring out what will work. Interesting thread.

Yeah, once you get used to Viton's oil and fuel resistance, it's easy to get lulled into thinking it's the cure-all for all automotive applications. I've thankfully not designed any obscure O-ring assemblies in my travels and I've not messed with brake fluids to date.

That will probably change if I get energetic and split my front calipers though. And at that time I will require a reading from the book of Parker.

BTW - A little off topic, but did you know that burning Viton is a really, really bad idea?

Hi all,

Finished rebuilding my brake switch. Luckely the bore was not too bad and cleaned up nicely with 500 and then 1000grit wet&dry. Made a hone out of a BIC pen by cutting a slot in it and using a 10mm strips of wet&dry.

280Z Brake Switch:

(The sizes are ID x Cross section. The material is EPDM)

The shuttle has two O-rings.

1x 6.07x1.78mm. AS010

1x 4.90x1.90mm. R4

The brake switch has an O-ring seal

1x 10.82x1.78mm. AS013

Proportioning Valve:

Not much luck on finding any replacement parts for it. I did find some cups that fitted, but the brake workshop didnt know which old car they came from. He just had a box of loose ends he kept out the back. He said, If I could find anything I could keep it.

Chas

i see that zcs in arizona has Brake Fluid Switch 12302302 @ 109.99 and np valve listed 12202401 price tbd

used - but better than nothing...

The last I have heard is that the np valve is now nla. I managed to clean mine up and reuse it. The switch just needed a set of o-rings. Its been 1 1/2 years and they are still working fine.

Chas