Trout...

I have had AP 6-pots on my car for some time.

Pedal feel as standard was OK - not spectacular - but required regular bleeding (brake bracket, braided hoses).

After fitting APs the pedal feel again was OK - but never quite as good as before - and although the brakes have never let me down it has deteriorated. The only way to get the same feel as other cars I have been in with APs and Alcons is to pump the brake pedal and eventually it gets firm.

There has always been substantial initial movement to bite....

...what could this be.

I have just completely flushed the system with new AP 5.1 fluid - no obvious leaks or broken seals anywhere, no obvious way air could have got back into the system after bleeding. Manifold vacuum pipe has been checked and is fitted with a proper hoseclip.

What are the possible causes of this? How can the system be properly tested? Could it be the master cylinder?

Any help appreciated - also car needs new front discs - where is the best place to take it to get the discs fitted AND the system checked over and sorted.

All help appreciated.

Trout

Pavlo

If ABS is fitted, have you recently given the ABS system a work out?

I have in this snow, and I think it just released a load of trapped air into the system. So I intend to bleed the brakes again.

When I did the fluid last time I flushed onces (loads of fluid to expel old crap) and bled 4 times (with a quick session on the road with ABS action after the second bleed), the last bleed I fed the outlet back into the master cylinder at the front and pumped for ages until I couldn't hear any air in the system. I know you're not supposed to do that, but by that time I had passed 1.5L of fluid throught the system, and it was all clean.

Also the brakes are link diagonally, so bleed them in diagonal pairs.

Other than that, don't know what to suggest.

Paul

Glenn_R

Hi Trout. Get the same with my AP 4's. They were superb on MY00 but have never been as good since putting them on the P1. No problem stopping but always a lot of travel on the pedal then not much feel after that to be able to measure your braking

Someone mentioned to me that it would probably be best to replace the cylinder, but no suggestion on what to upgrade to! Any ideas anyone??

Let me know if you have any luck with this one.

Glenn

PS. What pads are u using?

Trout...

I have a possible answer - there is a valve to the master cylinder - it could be leaking.

This would be correct as the amount of travel seems to be affected by the state of overrun.

I use Ferodo DS2500 pads - and they are very good!

Trout

JohnS

iTrader: (1)

Another possible thing could be front wheel bearings!

I had poor pedal feel on my old car for about 6 months. Changes pads and discs and it wasn't quite what it was. Tried bleeding the brakes with no improvement.

I noticed that if I "pumped" the brakes once before I needed to use them, then pedal feel was fine, which pointed to pad knock-off.

Had the fron wheel bearings checked, and one of them had some free play, though wasn't making any noises. It was replaced under warranty, and the pedal feel was a lot better after that.

John

Trout...

Thanks John - will check the bearings next time the car is up on the jacks.

The wheel bearings have done 55,000 miles and a few of those have been on track - thanks for your help.

Trout

BOB.T

If all that fails, whip the pads out and check that the friction material isn't pulling away from the backing plate

Trout...

Bob,

definately not that - is the same with new, old or part-worn pads.

Trout

Ed Hodgson

possibly worn brake master cylinder? - don't know how old the car is, but that's the problem I had with my sierra.

Can you push the brake pedal to the floor? - Push it hard & if the seals are poor, then the pedal will keep moving (slowly)

Cost me £30 to fix with a piston repair kit. If you can get a repair kit for the impreza master cylinder it might be a cheap thing to try.

ChristianR

iTrader: (1)

Trout, do your Ferodo DS2500 pads squeak a lot when uses the brakes? mine seems to when in slow moving traffic.

LeonT

triut where you from

Trout...

Yes my brakes do squeak!

No the pedal does not go all the way to the floor - but the bite point is very unpredictable. Once I reach bite pedal is hard and firm (fnarr, fnarr)

Leon, I am in Yorkshire!

Trout

KOZIKOT

I have the same prob, with ABS,and it turned out to be the rear brake's seal in the master cylinder,the rear brakes were hardly working ! Is there a repair kit available for the scoob master cylinder ?