Right i have a focus ST170, the brake pedal feels rubbish, dare i say spongey, there is NO air in the system, i have pressure bled the whole braking system 3 times and the clutch not a single pin prick of a bubble ever comes out. I used DOT 5.1, i have new pads which have bedded in now and stainless steel hoses. The pedal does not feel hard at all. If i pump the brake with the engine running it does pump up but never hard enough so that it prevents me from pushing the pedal to the floor. There is ZERO fluid leaking around the pedal, i lose no fluid, i just have no confidence in the brakes, dont get me wrong they work fine but i was expecting a rock hard pedal feel. When braking from High speed im sure if i braked hard enough the pedal would be on the floor????
What go on brothers, should i have used DOT 4 fluid? Have i got air in the ABS system?
PS before i made all the changes the pedal felt exactly the same.

 

You are aware that DOT 5.1 can have a much LOWER boiling point than dot4 ?, and is not the best you could use, originally it was developed for cold climates, nothing to do with racing etc, it was developed primarily for esp systems as it has much better cold flow than dot 4 etc.
Might be worth trying some dot 4 ?
tabetha

 

for what reason did the pedal go spongey in first place was it after fitting pads or hoses''s?

 

The pedal feel has always been the same, before the pads, hoses etc, it felt terrible, it feels just as bad now with no improvement. The only constant is that i have been running DOT 5.1 almost since i had the car...........shit its the fluid isnt it.......fuck it i will pressure bleed the system again but replace the fluid with DOT 4 or what ever is specified for the focus. The whole lower boiling point issue may explain why i lose braking completely when braking from over a ton to a much lower speed. Will DOT 4 give me my pedal feel back ?

 

Bleeding brakes with ABS I've found it helps after you bleed it once, go out and trigger the ABS, then bleed again. Sometimes you can still get air trapped in the system.
Maybe there's a problem with the MC?

 

I did think about the MC being the problem? but usually when the seals go the fluid leaks down the brake pedal? Thats not a bad idea regarding the ABS, i dont think it has been triggered since i changed the fluid. I will swap it for DOT 4 and then trigger the ABS and do a second bleed.

 

i have a similar problem on a mk1 mondeo, i have renewed the MC and servo and both made the brakes ok for a day then it went shit again.

i will try another bleed, then trigger the abs, then re-bleed.

haynes manual says rear calipers could be to blaim?

 

When you say rear calipers do you mean that the pistons could be seized or there could be air trapped at the rear??
I just wound the rear pistons in no problemo when i changed the pads so they are not seized and there is no air trapped there?
Maybe on the focus this is normal?
It frustrates me as i have driven many cars where the brake pedal is hard a a rock and very reassuring

P.S i remember why i chose DOT 5.1, in the technical guides that Stu at M Developments produced, it stated that DOT 5.1 had the highest boiling point and there was nothing really negative said about using it apart from having to change it at more frequent intervals??? Im now worried DOT 4 will feel even worse? And its definately DOT 5.1 i have been using not DOT 5

 

SOME(5.1) may well be higher but most are around 270C or so, most dot 4 are higher boiling points than dot 5.1 dot 4 typically being 315-330C boiling point DRY, wet it would be nearer 200C, for a road/race dot 4 fluid, it is considered "wet" when it has more than 2% moisture content.
The reason dot 5.1 don't need high boiling points is because they are a cold climate fluid developed for systems such as esp where improved low temp viscosity was needed.
tabetha

 

Tab you really know your stuff will update once i have changed fluid