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Okay so I have a 180sx which had R33 GTST brake gear on it (drum handbrake and all) and last year I decided to upgrade to GTST calipers to Brembo's from an R33 GTR.

Whilst I was at it I installed a BM57, new DOT 5.1 fluid, new pads, new DBA4000 rotors, new ADR approved braided lines etc.

Now the issue is that when the brake pedal is pushed upon the first push it is soft, then the second, is hard like it should be. The car still brakes by all means but its as if it has 50% of play.

Me and my mechanic bled the system 5 times and it still did the same thing, he had installed these brakes a couple times before and told me he's never had this issue. Thinking its vac related we did a smoke test but nothing came out.

But speaking of vac, when I give the car a hit and let off the accelerator or brake suddenly the revs drop rapidly and at times the car will stall. I just thought it was due to a lack of a BOV but I thought I would mention it if it's related to this.

Recently I have been driving my car pretty hard and I really would like the problem fixed, I just don't know where to start. Any tests I can do would be appreciated.

Here are the possible culprits I've been told it maybe:

- Faulty booster

- Play in the pads

- Air trapped somewhere it cant get out like the ABS unit

I would try bleed the ABS lines first, go around the block and safely try and kick the ABS then head back for a rebleed of the unit followed by bleeding your brakes again

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    • Hi, SteveL Thank you very much for your reply, you seem to be the only person on the net who has come up with a definitive answer for which I am grateful. The "Leak" was more by way of wet bubbles when the pedal was depressed hard by a buddy while trying to gey a decent pedal when bleeding the system having fitted the rebuilt BM50 back in the car, which now makes perfect sense. A bit of a shame having just rebuilt my BM50, I did not touch the proportioning valve side of things, the BM50 was leaking from the primary piston seal and fluid was running down the the Brake booster hence the need to rebuild, I had never noticed any fluid leaking from that hole previously it only started when I refitted it to the car. The brake lines in the photo are "Kunifer" which is a Copper/Nickel alloy brake pipe, but are only the ones I use to bench bleed Master cylinders, they are perfectly legal to use on vehicles here in the UK, however the lines on the car are PVF coated steel. Thanks again for clearing this up for me, a purchase of a new BMC appears to be on the cards, I have been looking at various options in case my BM50 was not repairable and have looked at the HFM BM57 which I understand is manufactured in Australia.  
    • Well the install is officially done. Filled with fluid and bled it today, but didn't get a chance to take it on a test drive. I'll throw some final pics of the lines and whatnot but you can definitely install a DMAX rack in an R33 with pretty minor mods. I think the only other thing I had to do that isn't documented here is grind a bit of the larger banjo fitting to get it to clear since the banjos are grouped much tighter on the DMAX rack. Also the dust boots from a R33 do not fit either fyi, so if you end up doing this install for whatever reason you'll need to grab those too. One caveat with buying the S15 dust boots however is that the clamps are too small to fit on the R33 inner tie rod since they're much thicker so keep the old clamps around. The boots also twist a bit when adjusting toe but it's not a big deal. No issues or leaks so far, steering feels good and it looks like there's a bit more lock now than I had before. Getting an alignment on Saturday so I'll see how it feels then but seems like it'll be good to go       
    • I don't get in here much anymore but I can help you with this.   The hole is a vent (air relief) for the brake proportioning valve, which is built into the master cylinder.    The bad news is that if brake fluid is leaking from that hole then it's getting past the proportioning valve seals.   The really bad news is that no spare parts are available for the proportioning valve either from Nissan or after market.     It's a bit of a PITA getting the proportioning valve out of the master cylinder body anyway but, fortunately, leaks from that area are rare in my experience. BTW, if those are copper (as such) brake lines you should get rid of them.    Bundy (steel) tube is a far better choice (and legal  in Australia - if that's where you are).
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