sti4

The other day I was out driving and i thought that my brakes were requiring a bit more pressure than usual. I put this down to the fact that i thought i needed a new set of pads. The problem has got progressivley worse,so today i thought i would investigate.

Pads were fine front and rear not even half worn. I have checked all pipework for any signs of leaking and checked the level of the fluid which was just under the max mark. I think this to be expected but to pads being half worn.

However the problem is getting worse. If i pump the pedal with the engine off the pedal gets hard. If i push te pedal when starting the engine the pedal falls away slighty which i am told is correct

However the pedal is really soft. If i push i can make the pedal hit the floor. But if i press and let go and then press again straight away the pedal is back to its usual self and the car brakes fine.

The other night i was coming to a roundabiut and i had to release the pedal and re apply.

It sounds like it could be air in the system but i dont understand how this may have happend or it culd be a faulty master cylinder I suppose. Oh yeah car isa 98stiV4 with ABS

JayPSC

Deffo air in the system, bleed the brakes & if it's still doing it then you've got air getting in somewhere or faulty MC. Same thing hapened to my Z after it'd been sat for a while, replaced MC & did a full bleed & it was fine.
Jay

DocJock

How old is the brake fluid ?

sti4

I would have thought over a year old. Wouldnt hurt to upgrade it really as i have a track day in january

How often should it be changed and does it degrade over time

Turbo_Six

Brake fluid absorbs water very slowly, but this will only affect the temperature at which it boils; contaminated fluid still won't become compressible at normal road-use temperatures.

My vote's on air in the system, if it's been a while you could change the fluid at the same time for not much more bother.

Water in the fluid will corrode the pipes, by the way, but not very fast.

sti4

I understand this but i cant understand the sudden loss of braking performance. One day it was fine then all of a sudden i had a spongy pedal. Think I will have to get up early and bleed the system.

waggy doo

iTrader: (1)

sti4 check my thread in wheels,tyres brakes. I have same problem.
I am pulling my hair out.

sti4

Right

I have bled the entire system and there was some air in the system. When i went back out it didnt feel much better to be honest, the pedal goes downs further than it did before all these probs started.

Then yesterday I thought i would go for a little drive and at low speed the abs is kicking in. I have no light on the dash to say that there is a fault with the abs.

Do you think the master cylinder is faulty or is there a prob with the abs. Can i get a repair kit for the MC or do i need to get a new master cylinder.

Cheers
Right

I have bled the entire system and there was some air in the system. When i went back out it didnt feel much better to be honest, the pedal goes downs further than it did before all these probs started.

Then yesterday I thought i would go for a little drive and at low speed the abs is kicking in. I have no light on the dash to say that there is a fault with the abs.

Do you think the master cylinder is faulty or is there a prob with the abs. Can i get a repair kit for the MC or do i need to get a new master cylinder.

Cheers

waggy doo

iTrader: (1)

Sti4
Take a look at my threads,spongy pedal,spongy pedal the sequal and spongy pedal the end.
I have been through everything,you name it and i had done it.You will see when you read the threads that the whole problem was down to play in front hub due to loose hub nut. Im not saying this will be your problem,but my brakes were perfect and then suddenly one day they just went soft.
Having tightened the front hub nut back up the brakes are great,actually better than i remember.
A wheel bearing problem can also cause same sort of brake fault.

waggy doo

iTrader: (1)

Oh one other thing, my abs kept messing about i think due to the hub moving towards and away from the sensor.Now all is well.

Carl2

Master cylinder? I had one go in a previous car and the pedal slowly made it's way to the floor over a few days until I had no brakes.
If you open the bleed screw too much you can let air in there and the brakes won't bleed properly as I found out on one of my cars. Just crack it enough to let the fluid out.

rb5 286

iTrader: (2)

if there is a loose, dodgy hub or hub bearing then this will cause the symptons you are experiencing, when u 1st depress the pedal, it goes to the floor then the 2nd press feels ok.

i had this once on my RS turbo, it happened with no warning, coming to a roundabout, pedal went to the floor,had to pump a 2nd time to get brakes. Hub bearing was fried and had lots of movement.

as waggy doo said, i would suggest u read his threads as u seem to have the same problem.

sti4

Once again the masters of Scoobynet come to the rescue!!

Jacked the car up and both rear wheels were fine, then the front and the passenger side wheel had a huge amount of movement in it. The garage that i usually use is shut till the new year so i have tightened the hub nut up reasonably tight and knocked the washer well into the nut.

Anyone know what the torque the hub nut should be?

Dread to think what would have happened a couple of week down the line especially as i was having a play with a 911 the other week.

waggy doo

iTrader: (1)

sti4
Glad you got it sorted,The front hub nut is150lb.The passenger hub nut on mine was less than 1 turn from coming off.scary ****

Martyn