Have to pump brake pedal to get a firmer pedal whilst driving.

7th April 2013, 12:09

Started noticing this yesterday. The brake pedal has been going between soft and hard, so say when parking, it will be really spongy, and suprise me as to how much i need to stop. Whereas like 4 minutes later the pedal will be nice and firm.

I'm thinking master cylinder is fucked?

7th April 2013, 12:30

Quote:

Originally Posted by m11ler

Started noticing this yesterday. The brake pedal has been going between soft and hard, so say when parking, it will be really spongy, and suprise me as to how much i need to stop. Whereas like 4 minutes later the pedal will be nice and firm.

I'm thinking master cylinder is fucked?

it could be alot of things, leave car over night with cardboard under each wheel check to see if any leaks, as i have a rear cylinder gone, was pissing out, i had same problem, spongy then very firm, it got to a point where all the fluid drained out and i had no brakes,

could be a split brake line or yes master cylinder,

7th April 2013, 12:58

Check all your calipers?

7th April 2013, 13:54

Bleed the brakes.

7th April 2013, 16:26

Quote:

Originally Posted by stevo67

Bleed the brakes.

This in the first instance.

7th April 2013, 19:49

Quote:

Originally Posted by stevo67

Bleed the brakes.

Quote:

Originally Posted by Ross

This in the first instance.

Cheers, i'll try this and report back

7th April 2013, 19:53

check your flexis too, i had one that was nearly rubbed through and eventually it burst on me.

7th April 2013, 20:06

Quote:

Originally Posted by Gandi699

check your flexis too, i had one that was nearly rubbed through and eventually it burst on me.

Flexis? Is that brake lines, i'm a proper novice mate. My mechanical knowledge goes as far as lego.

7th April 2013, 21:23

Yeah the flexi lines that link the calipers and one the ones on the rear that allow the beam to swing

8th April 2013, 18:05

Quote:

Originally Posted by Gandi699

Yeah the flexi lines that link the calipers and one the ones on the rear that allow the beam to swing

Okay cheers.

Also an update, after driving it more, i've noticed i have to actually pump the pedal to brake harder. So for example, going towards a roundabout, foot down, not a lot happening, foot off and on again, nice firm pedal.

Air in the lines? How would air get in the lines without any brake fluid leaking?

8th April 2013, 18:21

Brake fluid is hygroscopic. So, basically over time it absorbs water. The water boils and give you tiny bubbles. this is why you should change the brake fluid every 2 years

As above though, I'd be looking for leaks and then having your brake fluid changed for new fluid. Then look at vacuum to the servo and stuff?

What's the pedal like with the engine off? Press it hard and it should go down so far, but if it keeps falling that's certainly a leak, if it's spongy then it's air. (lots of air will allow the pedal to travel to the floor as well.)

If it's going between light and heavy pedal with the engine running then it could be a brake servo problem or you've got a tiny vacuum leak on the vacuum line for your servo.

That's all I know

8th April 2013, 18:33

Quote:

Originally Posted by MartinObviously

Brake fluid is hygroscopic. So, basically over time it absorbs water. The water boils and give you tiny bubbles. this is why you should change the brake fluid every 2 years

As above though, I'd be looking for leaks and then having your brake fluid changed for new fluid. Then look at vacuum to the servo and stuff?

What's the pedal like with the engine off? Press it hard and it should go down so far, but if it keeps falling that's certainly a leak, if it's spongy then it's air. (lots of air will allow the pedal to travel to the floor as well.)

If it's going between light and heavy pedal with the engine running then it could be a brake servo problem or you've got a tiny vacuum leak on the vacuum line for your servo.

That's all I know

I can cross the bold bit off, as its got 1 month old AP dot 5 fluid in it at the moment.
I'll check it with the engine off, cheers.

8th April 2013, 18:55

Quote:

Originally Posted by m11ler

I can cross the bold bit off, as its got 1 month old AP dot 5 fluid in it at the moment.
I'll check it with the engine off, cheers.

you mean DOT5.1? as DOT5 is silicone based and should not be used in a system which had DOT4 in it from factory as it eats the seals. (or so I was lead to believe) unless you have all new brakes or some shit like that anyway

Maybe I'm lying and it doesn't eat seals, or it congeals with any remaining bits of dot4 in there. that would account for spongy brakes?

I hope there's a brake expert on here

I'm very confused now.

8th April 2013, 19:07

Yeah dot 5.1

8th April 2013, 19:22

also jack up the car and see if theres any play in the wheel bearings by trying to rock them top to bottom and side to side.

Its possible that a wheel bearing could be worn allowing the wheel to move out of true which knocks back the pads in the caliper. You'd therefore have to pump the pedal to return the pads to the disc face before pumping it again to create braking force

8th April 2013, 19:33

With the engine off, all is as usual, the pedal can be pumped to a certain point, and is nice and hard, as it should be. Does that help anyone with a diagnosis?

8th April 2013, 20:19

thats how it should be...pedal goes hard. If the engines off then the servo isnt active.

Could also be a faulty servo or leak from its vacuum whilst driving causing you to have to pump the pedal

8th April 2013, 20:57

Quote:

Originally Posted by m11ler

With the engine off, all is as usual, the pedal can be pumped to a certain point, and is nice and hard, as it should be. Does that help anyone with a diagnosis?

That means everything is working ok,i`d still lean towards your brakes needing bleeding.

8th April 2013, 21:26

Quote:

Originally Posted by stevo67

That means everything is working ok,i`d still lean towards your brakes needing bleeding.

Ok cool, thankyou. I'll have a check for any leaks aswell.

9th April 2013, 20:20

Think we've found the problem. Got sent the wrong driveshaft, us being us, and in a rush, we didn't check it properly, just checked it was the right length and whacked it in.
Turns out its a tapered shaft for an early vtr. So basically it's not been sitting in the bearing properly, the wheel literally has a shit ton of play in it, causing the pads to compress on the disc, meaning i need to pump to lift them off.

Will be fitting a new driveshaft and bearing tomorrow, already contacted the company to see if they can do anything. Lesson learnt! Always check driveshafts properly!