Independent Renault Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter #1
As some of you know I had a problem of no braking power or pedal resistance when my car was running.

I replaced the rear pipes, wheel cylinders, master cylinder and servo, and bled the system to death.

The problem is still there.

The thing is its not like the brake pedal is SPONGY there literally is no resistance from the pedal for about the first 4 inches of travel. You can push it with your finger. THEN there is another half inch where the brakes work right at the bottom of the travel arc.

One thing im thinking is there something that regulates the amount of vacuum the servo draws from the manifold?

The final thing im going to do is strip down the servo and make sure all the seals are intact. However whats the odds of me buying a servo with the exact same problem?

It must be something to do with the vacuum the engine is drawing, there must be some kind of valve that regulates it..

Someone please point me in a direction as im tearing my hair out!
 

·
Premium Member
Joined
·
43,291 Posts
The brake system on your car is probably piped diagonally. I suggest you try this sequence
1. OSF
2. NSR
3. NSF
4. OSR

If you have a brake hose clamp you could try clamping each flexible hose in turn and see if anything improves.
Keep us updated:)
 

·
Registered
Joined
·
30 Posts
Discussion Starter #5
From the way the pedal feels, its not a case of air in the piper nor bad adjustment on the pads or shoes, it seems that the problem lies with the way the servo is working and handling the vacuum from the inlet manifold.

What has been suggested is that as i have replaced the servo, the rod that connects the brake pedal to the servo (the one that goes through the bulkhead) is adjustable and all i would need to do is give it an adjust to take up the slack as i do have good braking power but only at the last half inch of the pedal arc.

It seems a little too obvious and easy TBH but ill give anything a try at the moment. Someone, somewhere must have had the same problem and fixed it!

pw
 

·
Premium Member
Joined
·
43,291 Posts
When you bleed what type of pressure are you getting out of the bleeders. Was the master cylinder new or second hand. The master cylinder works on two stages the primary piston serves one half of the brakes and the presssure generated by it acts on the secondary piston serving the other. If the primary fails it will travel until it makes physical contact with the secondary piston and activate its circuit. When this happens you get excessive travel in the pedal - similar to what you describe. I would be very wary about adjusting the connecting link as all you may do is adjust the travel of the pedal but not solve the problem. If the servo was not working the pedal actuallly becomes harder but with reduced efficiency. I would start by opening the brake pipe connections at the master cylinder and see if air escapes and what pressure if any is emerging when you pump the pedal.:)
 
1 - 7 of 7 Posts
Top