Hi,

Octavia 1,9 TDI, built in 2007.

I had the LH rear caliper changed at a workshop (no Skoda dealer). No other parts were changed as pads and disk were still fine.

They did bleed the brake system afterwards (two times in fact). When I now drive and apply the brake, the pedal passes slightly the accelerator on the way down before the brake start working. That means, if I not place my foot very properly (which is unlikely in an emergency situation) I apply both pedals at the same time.

I am not quite sure, but it might also feel a little bit softer.

The people at the workshop were open and honest about it when the handed back the key. They said the old caliper may have been non-operational for some time and the pads might have to "adapt" again to the disk. In my view, this could explain a somewhat soft feeling in the pedal but not the extended travel, but I might be wrong.

They offered me to come back so that they could check further, but did not seem to have seen this kind of problem before.

Two things that I noted in addition (might always have been like this, but I never noted before):

With the car standing, but engine running: When I push the brake pedal several times, the point where it gives resistance (means where the brake starts working seems to come further up (towards me) with every push on the pedal.

With the car standing, but engine running: When I step on the brake with a force I would usually apply when using the brake strongly (but not emergency) and leave this force applied for say 15 sec the pedal will start moving down (giving way) for a certain way.

I would be very grateful if anyone has experienced something similar before and found the reason for it or if some just knows the inns and outs of this and could provide some guidance or explanation.

Thank you very much in advance!

Two things spring to mind, first is air in the system and the second is that they have bled the system incorrectly and damaged the brake master cylinder as a result.

They have done something wrong, the system MUST be pressure bled and not bled using the method of pressing the brake pedal up / down. If they have used the latter then the seals in the master cylinder have been damaged due to operating outside their normal range. This is not a problem on a newer car, but as the car ages the master cylinder workings get dirty on the parts that are outside, and this dirt then gets forced through the seals into the master cylinder and damages the rubber.

Two things spring to mind, first is air in the system and the second is that they have bled the system incorrectly and damaged the brake master cylinder as a result.

They have done something wrong, the system MUST be pressure bled and not bled using the method of pressing the brake pedal up / down. If they have used the latter then the seals in the master cylinder have been damaged due to operating outside their normal range. This is not a problem on a newer car, but as the car ages the master cylinder workings get dirty on the parts that are outside, and this dirt then gets forced through the seals into the master cylinder and damages the rubber.

Thank you very much! I do not know how they bled, but surely will ask!

Not been bled properly. I've never bled car brakes but all my bikes are hydraulic disc equipped and the symptoms you describe are in line with air in the system or possibly a fluid leak somewhere. You need to get it looked at. Don't even drive it...

I'd agree that they don't sound as if they've been bled properly.

As for the symptoms you describe when pumping the brakes or applying consistent pressure at idle, they are both normal.

Thank you so much for all the quick and valuable input. I called the workshop and will drop in there this afternoon. Based on your explanations I feel I can now ask more specific and qualified.

Will report back on the outcome.

I was at the workshop again. They did a new pressure bleed of the system and looked for and failure with the vacuum system without finding anything wrong. They tested the brakes on their test bench and found strangely enough that the rear ones act stronger than than the front.

That sound faily odd to me and I'm not sure what that indicates.

Other than that it was established that the two front brakes are equally strong and the same applies to the two rear ones.

We agreed that it is still not ok (even I found s slight improvement when driving the car). I have very little time for a few days (and no need for the car during that periode) but will be back at the workshop afterwards.

Again, thanks for taking the time to give me advice.

Which brakes harder (front or back) depends on the deceleration forces acting on the brake effort proportioning valve. I guess this won't be activated on a stationary vehicle on a test bed/rolling road.

The split of the braking force is adjusted to favour the rears under moderate braking in order to eliminate any suspension 'dive' caused by the front brakes.

Under heavy braking, the main force is instead directed to the front, in order to prevent the rears locking up due to weight transfer to the front.

Not disagreeing with any of the above, but if the previous rear cylinder had a seized piston then the pedal would feel more solid. My point is that you can't necessarily equate the pedal before and after. Hopefully brake performance will be chalk and cheese.

@skodacarman

What you write makes sense to me. Thanks for the explanation. The workshop guys apparently were not used to see the rear brakes being stronger than front. Therefore, given the strange fact that when braking normally in a usual traffic situation, the brake pedal will still pass the accelerator on its way down, I thought there might be a connection.I have never experienced something similar in any car I have driven (and that were quite a few of many different makes).

@nickguzzi

A good point you are raising. I experience what you say on the hand brake handle. It's not as firm as it used to be, but I think that because one caliper was not operating before.

Both hand- and foot brake performance are fine as far as I can tell (also what the workshop measured seemed ok).

What concerns me is that when I do not place my foot very properly when braking (and I most likely would not in an emergency situation) I operate the accelerator at the same time, increasing of course the way I need to stop .

I still can not understand what might cause this. A hydraulic brake system seems not so difficult after all...may be it is anyway

Again, thanks a lot for your advice

Hi,

just to close this and for future reference:

After being away traveling for a while I had the car now back at the workshop. They still did not believe me that they may have damaged the main brake cylinder and went through all the bits and pieces of the brake system first.

Then they concluded it might be the main cylinder anyway and replaced it. Brake is fine now.

Again, thanks for sharing your knowledge and advice.

Which brakes harder (front or back) depends on the deceleration forces acting on the brake effort proportioning valve.

If the car has ABS fitted it won't have a proportioning valve fitted as the main job of the valve is to prevent rear wheel lock up, which is exactly what the ABS will do.

I could be wrong here but I always thought the rear engaged just before the front to prevent nose dive..

Re-suspected brake master cylinder problems.

 

Can the brake master cylinder be disconnected and cleaned up?

 

Or would it need to be replaced altogether?