My brakes are seriously weak..

[PazzaAE86]

Shabba.


I moved my master cylinder over to fit this S50B30 M3 motor into my E30 and since then the brakes are shit.  Initally, for light braking they feel fine but they dont brake any harder than the initial press no matter how hard you stomp.

I've checked the one way check valve, i dont think there is an air leak between the car and the servo/booster and i think the booster is working.  (I pumped the brakes with the car off, started the motor and the pedal sank a little bit, suggesting the booster works?).  I dont suppose bleeding them would fix this issue?  I didnt loose any fluid while moving the servo and master over so i cant see why they would need bleeding.

Im confused.

[schlitz malt liquor]

I would start at re-bleeding first. does the e30 have abs??? pull the relay and gravity bleed. you still run the stock booster??? or you running hydro-boost setup??? As long as you don't have the booster hiss that my e30 had (put me into intersection doing 40mpg and I got t-boned)

[schlitz malt liquor]

[matt]

Where are you pulling your vacuum from?  Is there a small post-throttle-plate manifold?

BenS has a US s52 in his E30 and his brakes work great despite being a bit undersized.

[matt]

[PornStarSR]

When you say moved the master, physically moved it Changed its mounting location?

Could the place you mounted it be flexing under the force? Deflecting causing your force not to move the piston any further.

But Like others have said, re-bleed just to be sure.

[PornStarSR]

[PazzaAE86]

Car has ABS, gravity bleed?  Never heard of it, could you fill me in?  I've always bled by pedal mashing, i dont think thats good for ABS but still..

The booster is from a Renault Clio (smaller) but worked fine before the move, its sort of the done thing when converting to M50/S50.  The vacuum is pulled from the stock Euro M3 position, each throttle body goes to a collector which feeds the booster...

I had considered if the place i moved it to is flexing, i havent looked into it yet but i will...  I hope not, its got 2 skins on the bulkhead, is bolted to the dash brace and tranny tunnel too, just like OEM really..

Thanks

[matt]

sounds like a bad booster or your one-way valve is bad and/or in the wrong way.

[matt]

[Ben S]

sounds like a bad booster or your one-way valve is bad and/or in the wrong way.

Thats my guess as well. Or a vacuum leak on the motor. Have you unplugged the booster vacuum supply and see how much you are really getting?

[Ben S]

And if the booster is off center from the pedal enough that will kill some of the force applied from the pedal.

[PazzaAE86]

Checked the one way valve, i can blow through it one way and not the other, and it has been left in the posistion BMW intended as i havent fux'd with that part of the vac setup...  But i dont have any vac gauges or anything to see what vac im pulling..  Hmm.

But the booster could indeed be faulty, i cant rule it out really, as it is a used item afterall..

The booster isnt off center as such, RHD E30s have a linkage bar which runs across the bulkhead, that gets pulled by the pedal, which in turn presses the cylinder in..  So you cant really off center it, just have to extend the linkage bar.

[Ben S]

So it sounds like your booster may have shit the bed. If you have access to a vacuum pump like the ones used for ac work you could hook that bitch to it and see if the pedal softens up but if its cheap and easy to try a different booster i would try that. I run a e21 booster with a shortened push rod in my e30 m3 with a us s52 and its a little higher effort then stock but still works very well.

[schlitz malt liquor]

hopefully its simple like the booster. if not. the bleeding process you can simplify by pulling the abs relay. it opens the braking circuit to function like non-abs. it would be faster to flush with vacuum bleeding, it was over 20 pedal pumps 5 times per corner to fully flush the system on my e30.

[schlitz malt liquor]

[PazzaAE86]

In the news today, the hydro handbrake works fine, locks the rears no worries...  Thats un-assisted as its further back.  Booster is looking likely?  I dont know how people run boosterless on these cars, it will not stop no matter how hard you press the pedal...  Just slows at the same rate..

Cheers

[carbotron]

if booster checks out ok, maybe the pushrod is too short/long? wrong pivot point in the pedal or chassis or something?  you saying this all worked before? what didn't you move over? hows that interfacing with what you did move over? good luck

[carbotron]

[Ben S]

Like a dumb ass I forgot to ask is the pedal low at all? Like do you have to push it further then before to get the brakes to engage? If not bleeding is not the issue. If you have a one or can get your hands on a small hand held vacuum pump with a gauge on it which you can buy for aroung 40 bucks hook that to the booster and pump it up. If it doesn't hold vacuum and bleeds off there you go you have a torn diaphram in the booster. Easy way to be sure. 

[PazzaAE86]

My booster hisses when i shut the engine off.  Just wondering, i remember when i removed the master cylinder there was a rubber o-ring that goes around the back of the cylinder that had split.  I replaced it with a generic o ring..  I cant imagine that seals anything in particular but i could be wrong, perhaps my generic o ring isnt good enough?