s13 brake problems, z32 parts, help please

[jp86]

OK here's the problem I'm having, with all the back ground information below, is that 1/3 of the time, while driving when i use it, my brake pedal feels fine and nice and hard and the brakes are responcive, the other 2/3 of the time the pedal drops about 2" (with very little pressure) then the brakes feel nice and hard and responcive. it seems to be totally random, and it's always with the motor running and driving around.

ok so the car I have is a 89 s13 with abs, the brake mods are braided lines front and rear and front 30mm z32 calipers and a 1-1/16 300zx master cylinder.

the master cylinder is new not rebuilt, the calipers are all rebuilt and have no leaks, and the braided lines are also new.since my car is a abs model I used the 2 fittings on the 300zx mc that are ready to be used......the furthest front and furthest rear one.

from my seaching this is the proper way to hook it all up, every piece was installed one by one and prefilled with fuild, the system was never left to drain, none of the fittings was left open for more then 2 minutes and even then it was capped with a finger till the new part was to be threaded in.

I then bled the brakes in the proper order for the abs cars which is, rear drivers, rear passenger, front drivers, front passengers, then the front abs and then the rear abs, until there was no more air to be found.....and I've done this several times now to be sure.

any help with this annomially would be great, I use to work as a mechanic and have never had soo much trouble.thanks

jp

[jp86]

there's no fliud leaks anywhere....it just seems like the pedal just drops 2" before working normally sometimes while other times it works fine and the pedal stays nice and high.....

when i bench bled the master it worked fine and I've broken loose the 2 fittings on the master while someone pushed the pedal and got good pressure out of both. both times the pedal is firm but sometimes it goes down 2" before if gets firm with no brakeing happening in that 2" of travel??

jp

[NISTECH]

this sounds more like a brake booster problem. get a vaccum gauge teed in the line and run enough of it to see it while driving. See if you get different readings for each instance.

[jp86]

ok sounds good thanks alot, i thouhgt it might have been a bleeding problem but now that I think about it the brakes are always firm when I use them...the only thing that's changing is the pedal travel.

jp