Hi, 

 

So i have been searching around and i can't find another post that quite describes the problem i am having with the brakes on my 55 plate 1.9TDi Octavia Estate.

 

Usually the brakes works fully within the first few inches of pedal travel as they should however recently they have developed an intermittent problem where the pedal will push straight past this point and not start working until very near the floor, once you reach this point the brakes seem to function as normal with the normal amount of power however it is obviously not right. The problem is seemingly random happening sometimes for a few hours before'fixing itself' and most recently it lasted for a month before fixing itself (this coincided perfectly with me handing it over to a garage to diagnose the problem who called me later to ask me what the problem was because it all seemed fine to them  ).

 

Since the problem began i have changed all the brake pads, this made no difference. When the engine is on, under constant pressure the pedal sinks very slowly (due to the servo i am told) and when the engine is off the pedal pumps up as normal and, under constant pressure, does not sink to the floor (a sign the the master cylinder is ok?). 

 

I am at a loss here, does anyone have any insight into what might be wrong or any further trouble shooting i can do?

Any help appreciated

 

Thanks,

 

Chris 

Hmm, my brakes are not doing quite the same, but occasionally sink more than normal in a similarly random fashion.

 

Same behaviour as yours when stood still.

 

Next week I have a full set of front + rear discs and pads to go on. 

I've already had the brake fluid changed.

Chris, when did you last change the brake fluid?

 

Softscoop, sounds like you still have some air in the system. Try bleeding again and if that doesn't work then you may have seal that has gone.

I doubt there is air in the system as I didn't change the fluid. It was done by a local VAG specialist.

 

It's there next week for the discs + pads, I'll get him to check it out.

Even if done by a garage doesn't guarantee it been done correctly but if it's booked get them to check it. When did your pedal start going soft and was there any work done on it around the time?

Chris, when did you last change the brake fluid?

 

Softscoop, sounds like you still have some air in the system. Try bleeding again and if that doesn't work then you may have seal that has gone.

No idea, not since I bought the car around 2 years ago. How would old brake fluid cause a problem like this?

As brake fluid gets old its properties change so that it looses its performance, hence why all your skoda manuals mention changing the brake fluid every 2 years

Edited 15 April, 201610 yr by robt100

Brake fluid absorbs moisture over time which can lead to vapour locks. A vapour lock would only occur with very hot brakes, when the fluid in the caliper rises above 100 deg c and the water in the fluid boils and enters a vapour state. You then can lose brake pedal action as the vapour is easily compressible. This may be what is happening, so

1. Change the brake fluid and...

2. Check the brakes are not binding, which usually happens when the pads stick on the carrier because of corrosion. Are the discs getting very hot even though youre hardly using the brakes? To fix this you need to remove the caliper and pads and clean the carrier slides, calipers and pads backing plate where they slide along the carrier. You may need to use a file to remove the corrosion and reassemble using Cer-tec non metallic brake grease to lubricate the slide areas and the caliper slide pins.

You might as well change the discs and pads if you do this unless the discs and pads look fine.

Edited 15 April, 201610 yr by xman

Brake fluid absorbs moisture over time which can lead to vapour locks. A vapour lock would only occur with very hot brakes, when the fluid in the caliper rises above 100 deg c and the water in the fluid boils and enters a vapour state. You then can lose brake pedal action as the vapour is easily compressible. This may be what is happening, so

1. Change the brake fluid and...

2. Check the brakes are not binding, which usually happens when the pads stick on the carrier because of corrosion. Are the discs getting very hot even though youre hardly using the brakes? To fix this you need to remove the caliper and pads and clean the carrier slides, calipers and pads backing plate where they slide along the carrier. You may need to use a file to remove the corrosion and reassemble using Cer-tec non metallic brake grease to lubricate the slide areas and the caliper slide pins.

You might as well change the discs and pads if you do this unless the discs and pads look fine.

Thanks for the help. I understand that changing the brake fluid is probably a good thing to do anyway for general maintenance of the car however the problem i am having occurs from cold, it might start mid way through one journey and continue into the next one as soon as i start the car (lasting several drives at a time over a long period of time.)

 

When i changed the pads the pistons all seemed to move smoothly enough when winding them back out and not be binding although i will keep an eye on this. The discs seemed to be in good shape without any large lips or grooves on them so i didn't change them.

One possibility is a problem with the master cylinder. A seal may be failing on one of the two pistons.

Might be worth looking up above the brake pedal for brake fluid leaking from the master cylinder through the bellows and along the pedal rod.

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I have started to have the same problem same car and year.I had rear calliper changed because of sticking on the drivers side a few weeks later it started so today I changed the passenger side but it happened again after about 6 miles of driving .We have no fluid leaks and both rear flexi hoses have been changed.Pedal sinks down slowly then I pump it again it's ok .Could be fine for days,then go again .Going to another garage tomorrow let you know how I get on as I am a cab driver and need it done ASAP

Personally I'd get the brake fluid changed.

Id also get the garage to check of there's any leaks on the system.

Not sure about the octavia bet had this on some golfs and jettas and its possible for air to be in the system around the abs unit and needs vag com to bleed it. Tricky and messy but usually sorts the problem.

Ok so in case anyone with a similar problem comes across this, i seem to have had the problem fixed (it's a little tricky to tell due to the fact the problem comes and goes however its been a few days and everything seems to be back to normal). In the end i had the master cylinder changed and that seems to have been the problem (despite the garages initial diagnosis that there was nothing wrong with it).

 

So there you have it, after several trips to numerous garages the initial solution i came across on this forum in about 10 mins of googling turned out to be the correct one. 

 

Thanks for all your help guys

air in brake fluid.

 

brake power assistant (unsure about english word)

 

ABS pump gone

 

stuck rear callipers if you have one

 

Bleed the brakes and you'll see.

air in brake fluid.

 

brake power assistant (unsure about english word)

 

ABS pump gone

 

stuck rear callipers if you have one

 

Bleed the brakes and you'll see.

Read the post above yours, where the OP describes the solution found.

On 5/31/2016 at 22:03, chrispleass said:

Ok so in case anyone with a similar problem comes across this, i seem to have had the problem fixed (it's a little tricky to tell due to the fact the problem comes and goes however its been a few days and everything seems to be back to normal). In the end i had the master cylinder changed and that seems to have been the problem (despite the garages initial diagnosis that there was nothing wrong with it).

 

So there you have it, after several trips to numerous garages the initial solution i came across on this forum in about 10 mins of googling turned out to be the correct one. 

 

Thanks for all your help guys

same problem on my octavia 1.9 tdi all wheel bleeding done by several time by using vag and manually all brake pad is great condition but still soft brake pedal. so can i change Brake Master Cylinder?