Disco 200Tdi Brake pedal creep

Hello

Must say great forum, have found it very useful in past.

Unfortunately tried a few different searches and didnt find the answer to my problem this time.

When braking my brake pedal starts to creep down, making it very long, almost liek I have no pedal, although no extra force is required to make the car stop, it stops fine.

I have checked haynes manual, checked the brake servo valve, thats fine, can only blow in one way. Also checked pipes and all seem to be connected. Also when car is off pedal is nice and firm, its only when I turn the engine on that the pedal starts to creep.

So I am guessing its some sort of vacuum problem, although the servo functions correctly according to haynes. So this leaves the vacuum pump and master cylinder? Any way I can check?

If the pedal doesnt creep when car is off surely that rules the master cylinder out?

Any help much appreciated.

thx

Sounds like the brake system needs bleeding.

If you pump the pedal on and off three or four times does it harden up? If so 1st job is bleeding the air out of the system and seeing how it goes after.

I was hoping that! I tried with an easy bleed kit as didnt have a second person to hand and wasnt any air coming out so ruled that out, but will have another go with a friend.

(Yes it does harden up when i pump)

It occured around the same time as I changed a wheel bearing and I repmember pushing the brake pistons back into the callipers without loosening the bleed valve.

thx for the reply

Last time I did mine I seem to recall doing it in sequence .. can't remember offhand, think it nearside rear, offside rear, nearside front then offside front .. but I just checked Rave and it doesn't say it needs to be done in sequence at all!!

I wonder if I'm getting the Disco and my old S3 mixed up!

Would air in the system not have an effect on the brake creeping when the engine is off? Hence why I thought it was related to vacuum. Wont be able to work on it til weekend

Are you loosing brake fluid?

It hardens up the pedal when he pumps it - there's the clue.

It almost certainly needs bled properly.
A stuck piston in one caliper can cause the same sensation, or a brake pad not sitting correctly in the caliper frame, and even soggy seals in the master cylinder.

Bleed it first very thoroughly.

CharlesY

No brake fluid loss.

thx to all above. Will update once get it bled properly.

My bet is a duff master cylinder.

I second Soloby Rob, Its sound's like you have lossed one circuit out of the master, If no fluid loss its likely to be the Master, With air in the system you should be able to pump up and hold with no pedal creep,

Ivor

I have a disco 200tdi I had the same thing when you bleed the calipers there should be three nipples on the front ones, you have to bleed the the lower pair together,then bleed the top one to to build up the pressure by only just opening it slightly,I usually do the back first its easy because there is only one nipple, and as your have been told farest to master cylnder down to nearest. Hope it helps.

ivorantony said:

I second Soloby Rob, Its sound's like you have lossed one circuit out of the master, If no fluid loss its likely to be the Master, With air in the system you should be able to pump up and hold with no pedal creep,

Ivor

Click to expand...

Would it not creep when the engine is off though also?

Swapping master cylinders looks like an interesting job....

swapping master cyls is relatively straightforward...as to bleeding sequence: furthest from master cyl first then work back towards it.But like charlesy says,bleed it RIGHT OUT first,ie; new fluid throughout....its amazing what a bit of contaminated fluid will cause

I have just remembered that my pedal creep stopped, when my rear caliper pistons and seals where changed, they were jamming. And keeping my foot on the pedal caused it to creep down, its a cheap repair parts from Paddock.

Pedal creep is normally a faulty cylinder / calliper (seals etc).
The reason you don't notice the creep when the engine is off is the servo assists your foot by making the force on the master cylinder greater than just the foot alone, so the creep is worse with the servo working (if you don't notice it without the engine then it's just not got bad enough or you're not pushing very hard).

Spongy pedal is normally air in the system somewhere. This can also be thought to be excessive travel, but the difference is how the pedal stops, if it's soft, soft hard then it's excessive travel, if it's soft, neither soft nor hard then hard then it's air.

Excessive travel is normally brake adjustment, shoes having to move out a long way to contact with the drum, so it takes a lot of fluid movement to get them there.

Ineffective brakes with the engine running- brake pedal doesn't move down when applied then engine started (get rid of all vacuum first) is a servo issue, normally servo isn't getting enough vacuum supply.

Ineffective brakes with engine running- pedal moves when engine is started but keeps pulsing, servo issue, there's a leek in the servo itself generally.

Brakes ineffective, but none of the above is normally something wrong at the corners, pads/ shoes F***ed, callipers sticky etc.


I think that covers most brake issues excluding parking brakes.

Try bleading the brakes from the master cylinder, to do this you must put a cloth under the master and have a nother person with you get them to pump the brakes up and hold the pedal down when you slacken the brake pipe on the master DO NOT TAKE IT OFF just enough for any air that is inside it to come out then tighten it up and repeat on all others BUT DO NOT TAKE IT ALL THE WAY OFF OR YOU WILL BE IN TROUBLE.

it is easyer to blead the master this way and sometimes if air is in the master its a bugger to blead out if you dont do it this way

Done all the brake pipes on my landy today including new master made all the pipes up my sulf

Gave it a good bleed and no joy!

Although while bleeding as I had a spare hand to pump the pedal, I noticed the fluid in the brake reservoid releasing a bit air bubble everytime pedal was pushed. Does this point to master cylinder?

I have seen this on a couple of cars not just Disco's, when the pistons are pushed back into the caliper fluid rushes back into the master cylinder and disturbs the sediment in the reservoir.

This can then get trapped in the seals/bore of the master cylinder allowing fluid to get past the seals and move back into the reservior. To discount calipers ect try clamping off each caliper with a BRAKE PIPE clamp!!

Sorry for shouting I must have seen to many molegrips being used without some form of padding.

This problem can also occur after routine brake fluid changes.

If the servo was faulty the pedal would be very hard to push down and would disguise the pedal creep engine on or off.

Add that to the other comments made and you are sure to find the fault.

Make sure you come back with the remedy it will help others at a later date.

regards

Dave

Hi guys,

I've got a simmilar problem on my 200 TDi Disco...

Once in a while (typical! ) my brake pedal will go hard, maybe an inch of travel, brakes barely work.

Sometimes when I depress the brake, I get a small "hiss" from somewhere near the pedal.

I'm planning on getting a non-return bleed kit then bleed them, but I think this sound more like pipes or servo from what I've read here?

How would I test if it's the servo?

Any one any other ideas / confirmation?

Thanks in advance, not keen on having "iffy" brakes!

Just found this.. would you guys agree?

Yes it's only can be vacuum problem. Maybe the vacuum hose has broken somewhere and the vacuum cannot go to the vacuum servo drum. Or the hose is loosen.

Third variation is the vacuum drum is flown the vacuum.

So, if the pedal was hard to push, than It was vacuum problem I'm sure.