I got myself a 510 couple of weeks back and been trying to get it running. Well, its moving now..but stopping is the main issue. The brakes are bad. When i hit the pedal it goes all the way to the floor. There is some kind of "feel" on the pedal but its far from sufficient. Assuming the car is still, the brakes are good enough to hold the car when parked at a slope. But when it starts moving, its weak, very weak.

This is what i have done so far:-

- Bleed the brakes (all 4 sides), but no difference
- Changed the master pump to a new unit and bleed the brakes again, but no difference
- Changed the servo (swapped from another car which was working well), no difference
- Serviced the front calipers and replaced the rear brake pumps, bleed the brakes, no difference...
- Ensured there's no vacuum leak from manifold to servo


Im trying other ways to troubleshoot this problem, but any tips from you guys is much appreciated. Thanks

Are u using a brake booster??

Yes, booster = servo (same meaning). And i've replaced this from another car which was working fine

Are you losing fluid at all??

No. Fluid level never drops, unless i bleed the brakes.

Can it be that the proportioning valve (a.k.a brake body pump) is faulty?
As i know, it has a one way valve to hold the pressure. What if the valve is damaged? Fluid can travel both ways and there's insufficient pressure to the brakes...

Hmmm..does this makes sense?

it is either leaking fluid somewhere or sucking air or the master's not working.

do you get any air when bleeding the calipers?

did you bleed the master cyl?

what are rear brake pumps? wheel cylinders? ie drum rear brakes? have you adjusted them?

answers to your question:-

-no leaking fluid
-no vaccuum leak
-new master cylinder

-initially had air, but its completely fluid squirting out now
-master cylinder bleeding - i didnt do this, thought that bleeding at the brakes end would be sufficient. Do i still need to do this even after i have used up almost a litre of fluid for bleeding at the brakes end?

-rear = drums. Already adjusted until the wheels wouldnt turn, then slightly loosened it until i can feel some level of resistance

I back bleed the system (pump the fluid in from bleeders) or use a tool know as Mighty-Vac. Get the car up on jack stands and have someone put the brakes on and examine the connections. Also how old are the brakes lines??

Tom

When you rebuilt the calipers did you put them back on the correct sides of the car... bleeders to the top ?

Clamp the flexible hoses at each wheel
Try to isolate whether its a front caliper or the rear causing the issue

My guess is the pistons are rolling back on the seals when you release the brake and they have to travel too far to reach the pad/disc each time causing the low pedal