Trying to give my brakes(4 pot powerlites) a proper bleed,but still cant get a "good" pedal feel......its soft...its a stock master cylinder,wilwood proportion valve rally design hydro handbrake with a 0.625 cylinder,and sierra rear calipers....even the handbrake feels soft.....and the rear calipers are serviced

Have you got the bleed nipple at the top on the rear calipers???

if not, thats probably why

I do have th bleed nipple at top Ben,

Didnt understand to be honest....u saying that the nipples are tuching the disc?

quote:

---

Originally posted by madteg
Bet you have trapped air in rear calipers, i had toy to through the towel in. remove calipers and make shaw the bleed nipple was at the top but still on the disc so pistons dont pop out. worked for me as i was ready to through the towel in.

---

I had this. Then I tried bleeding the brakes whilst tapping the caliper with a spanner and a shed load of bubbles came out of one caliper bleed pipe. Job done

Still don't understand where they were trapped but hey.....

Actually the 1 gets more sticky than the other 1....so ill give them tap too...

No worries
so might what happening?

Still think its rear calipers, if your calipers are mounted vertical the bleed nipple is at the top but there is a pocket of air just above them. you have to have the nipple highest point. On the sieera the calipers are mounted at about 40 deg, let us know what you find. kev.

Just checked them and the nipples were facing down... now there up...feeling is kinda better but not ideal...u think my MC has to do with?
sorry for the bad pics

Assuming you have carefully checked every joint in the system for tiny leaks the only possible causes of your problem are trapped air or mechanical flexing.

If after correctly bleeding the system turing the calipers to ensure all air can get out via the nipple . If after that you still have a spongey pedal it is mechanical flexing of the calipers or caliper mounts or hydraulic hand brake bracket.

To cure it you could spend a couple of days hand fettling and checking with feeler gauges to get the calipers sitting 100% square to the discs in all 3 axis, then if you still a spongey pedal more time checking the pedal box and hand brake bracket for flexing with a dial gauge. After all that I am pretty sure you will still have a pedal that is at least a bit spongey because multi pot alloy calipers flex under hydraulic pressure.

If you want decent brakes the simplest cure is ditch all the bling stuff including the hydraulic handbrake and pressure regulating valve which will have no effect anyway because the line pressure on a Locost style car are too low.
Replace the whole lot with standard Sierra bits and change the mastercylinder for a Lada/FIAT 124 part. This will give you better stopping power and a road legal handbrake the only downsides are the loss of bling and the increase in unsprung weight.



[Edited on 18/7/10 by britishtrident]

Thanks for ur answer,the car is not for road use so dont care about been legal,will the fiat MC be a bolt on thing,and can i keep the rest of my set up with it?

No the FIAT master cylinder if used with the Powerlites will make matter worse.

Your mastercylinder is almost certainly working properly, you can test it and the stiffness of the pedal box mounting by simply undoing the pipes and replacing them with bleed nipples. After a quick bleed the pedal should be rock solid.
If calipers are truly parrallel to the disc in all 3 axis and you still get a spongey pedal then the problem is caliper flex.
Alloy calipers flex much more than cast steel ones and the more pots a caliper has the more it flexes --- ie a long skinny caliper with flex more than a short fat one.

OK,i ve read that putting a piece of wood against the pedal and leave it there overnight might help of sending the air back,and check-tap-bleed the system individually might help....