Really Poor Braking at Low Speeds

[Aby]

My friend's Skoda Octavia MK2 L&K Diesel 2007 1.9 PD is having braking issues at low speeds. I recently drove the car and found that the braking is just fine at higher speeds, but when the speed is below around 40kmph the brake pedal just goes down to the floor while braking.

We checked the vacuum pump by releasing the main line. On idle and at low RPM, vacuum can be felt in the lines. So does this mean vacuum pump is alright? All the vacuum lines has also been checked for leaks or blockages, we found none. Will there be a problem with brake booster? VCDS scan did not bring about any faults on the ABS Unit.

Any suggestions?

[Gti Jazz Blue]

Loosing Vacuum would result in a harder pedal as you are loosing assistance, it would suggest some kind of master cylinder issue to me if the pedal is going to the floor.

[Aby]

Will have a look at it, can it be the brake boosters? Also how do I check vacuum pump to see if it works correctly? Can I do it using VCDS?

[Gti Jazz Blue]

Not an expert on the 1.9TDi - but I'm pretty sure that you couldn't on the 2.0TDi so I'd doubt it - you are going to need a vacuum tester. As I say though I would expect a loss of vacuum to go the other way in that you would loose assistance and the pedal would go hard, but I'm no expert.

[nick74]

Yes I've had a vac pump fail on a previous car and it did make the pedal go rock hard and very difficult to press, not sink to the floor.

 

My guess would be a problem with the seals in the master cylinder

[Aby]

Thanks for the advice guys, will check the master cylinder. Is there anyway to get readings of Vacuum Pump using VCDS?

[mannyo]

Vacuum is not monitored anywhere, and as posted I suspect is working fine otherwise you'll have other symptoms with the cars running.

I'd be heading for the brake master cylinder. If the system has had a fluid change and was not pressure bled, then the seals in the master cylinder will be damaged. The brake system must be pressure bled, if it was done using the footbrake pumping method then it is very easy to damage the seals.

[targus999]

me too had the same problems its related to brake master cylinder 

the pedal would sink to the floor 

did u replace the brake fluid ? 

 

[Aby]

Update: Seems like the issue is fixed. Cleaned the vacuum lines properly and the issue seems to have fixed. The car has been driven for around 500 Km's now and the issue has not cropped up. Hope it stays that way. Thanks for all the advice guys.