Long Brake Pedal, Help Needed

[parry 23 1 Cars]

Hi all,

 

Symptom:

 

With engine running I have a long soft pedal, the pedal travels about 3 inches before it is firm and braking pressure is applied. When you depress the pedal you can actually hear hissing from inside the car, is this normal?

 

With engine off the pedal is firm with no travel.

 

This was the same with the standard calipers, this only started to happen when I put the new master cylinder in.

 

Could it be a leaking booster or is the MC shaft short than standard and the pedal needs londer travel to compensate.

 

The car is a dedicated track car and would like a very firm pedal. Any help would be apreciated.

 

Search was performed and no luck.

 

PA

[mrswampy 0]

Fairly sure you can adjust part of the mc or servo to help with that problem

 

rippthru knows how to do it

[pugbender 0]

i also noticed this in my 205 with 307 brakes and fiat scudo MC that is bigger +1mm compared to the std gti item.any help?

[vickiw106 1]

you may need to adjust you pedal box/servo

 

to do this you have to remove the mc, get some one to push the pedal to the floor and you will see the push rod.

 

with a pair of grip hold the rod and wind the end out

 

be carefull though dont take it to far you still need to make sure the mc will fully close as the mc will keep the pressure in the system and you brakes will bind on

 

hope this helps

[parry 23 1 Cars]

you may need to adjust you pedal box/servo

 

to do this you have to remove the mc, get some one to push the pedal to the floor and you will see the push rod.

 

with a pair of grip hold the rod and wind the end out

 

be carefull though dont take it to far you still need to make sure the mc will fully close as the mc will keep the pressure in the system and you brakes will bind on

 

hope this helps

 

Will try that now and let you know how I go. Thank you.

[Super Josh 4]

When I fitted a 406 MC (23.8 mm one) I needed to extend the servo rod by about 1mm. I just measured the depth of the recess in the MC with a vernier caliper and the measured the pushrod length and worked out how much to extend it by.

 

Just make sure it isn't too long or the brakes will bind on.

 

 

Josh

[DRTDVL 4 1 Cars]

I know a few guys here have used the 405 T16 MC (it's the same as a few other models - just sounds cooler) with great sucess.

 

There was no need for adjustment.

 

I've got the 307 fronts on my 306 without the new MC and it's a bit soft. It made a massive differance when i just replaced the front brakelines as the old ones where the ones from the factory and although the outside looked fine the inside of the lines where screwed.

[Spiky 37]

with the 307 brakes, a 205 MC is sufficent, as they have a smaller piston than the gti6 brakes, which normal give the symtoms you have.

 

but ou can alter rod to suite, becare not to extend the rod to much else your brakes will be on even without your foot on the pedal

[parry 23 1 Cars]

Ok here is the latest.

 

I removed the MC and all looks to be ok. The rod on the booster is 21mm away from the face. The MC contact point is 21mm away from the face. So no need for adjustment.

 

I checked the rod and as soon as you start to move the brake pedal the rod moves as well. So no play in the pedal.

 

So why would the MC take 2 inches or so before pressue is applied to the brakes? Is there a process on bleeding the master cylinder, or does the normal brake bleeding process work?

 

Also lets keep in mine here that I am running a drum rear end with the compensator in place, the Australian delivered GTis were 1.6 configuration.

 

I am at a point where I might go extreme and just get a proper pedal box with a bias adjuster. Remove the compensator while I am at it as well.

 

Thanks for your comments so far guys, we will find a solution.

[welshpug 1,621]

how accurate was that measurement of 21mm?

 

the haynes manual has a specific dimension of 22.2 to 22.4mm.

[parry 23 1 Cars]

Will measure again tonight and let you know.