Problem With The Brakes

[Crosswind]

Hi guys

I have a small problem with the brakes of my Kia Cerato.

As soon as the car is started, the brakes don't work well. When I reverse the car from the parking position, the brakes work only after slamming the pedal hard.

However, in less than a minute or so it becomes normal. Braking is pretty good thereafter.

What could the problem be? Air in vacuum lines? ABS trouble?

Note: the car has disc brakes all around

Thanks in advance

[terrabytetango]

When the brakes are weak, is the pedal hard or spongy, or is there no difference? And is it only in reverse they appear to be weak?

[Crishan]

  On 11/25/2015 at 11:13 AM, Crosswind said:

Hi guys

I have a small problem with the brakes of my Kia Cerato.

As soon as the car is started, the brakes don't work well. When I reverse the car from the parking position, the brakes work only after slamming the pedal hard.

However, in less than a minute or so it becomes normal. Braking is pretty good thereafter.

What could the problem be? Air in vacuum lines? ABS trouble?

Note: the car has disc brakes all around

Thanks in advance

Happens to me also. I have to reverse to take the car out of the garage. Before I select the gear, I hit the brak twice and reverse. Or else for sometime the break pedal does not work well. Stafford said no issue when I raised my concern.

[Crosswind]

  On 11/25/2015 at 12:37 PM, terrabytetango said:

When the brakes are weak, is the pedal hard or spongy, or is there no difference? And is it only in reverse they appear to be weak?

No difference when the brakes are weak. Pedal feels as usual but the car don't seem to stop. It's just for about 30 seconds after starting.

This is irrespective of the gear (D or R)

[terrabytetango]

In that case, the same happened with my Vios as well. I chalked it up to the pads being worn one way, so they're less effective in reverse. But then I only reverse my car once a day, so I dunno if it continues after the first minute.

[Rumesh88]

The manifold vacuum available for the brake booster is less at cold start and hence may take a little longer to build up but still it could be the sign of a small vacuum leak. There must be a small notch-like indentation on the under side of the booster body where it meets the master pump (difficult to see it from top sometimes). When the engine is cold you may temporary block the notch with something like a piece of modelling clay, chewing gum etc and test if the situation improves. However, make sure to remove whatever used to block the notch immediately for it is a safety vent which,if kept blocked could result in brake fluid being sucked into the booster. (In fact I found a KE20 booster with more than half litre of fluid accumulate inside the booster cos a maka bass had kept the notch blocked ) You may test for booster leaks as explained in this thread http://forum.autolanka.com/topic/15409-break-issue/?hl=%2Btest+%2Bthe+%2Bbooster#entry246073 or http://forum.autolanka.com/topic/15491-car-is-not-speedup-when-accelerating-bad-smell/page-2?hl=%2Btest+%2Bthe+%2Bbooster#entry247782

Edited November 25, 2015 by Rumesh88

[Davy]

Agree with Rumesh about the possibility of a vacuum leak. The duration within which you feel the loss of braking power the time where the vacuum is trying to overtake the leak, but is still behind.

Is this a new Cerato Crosswind? If so, I think the vacuum for the booster is not supplied by the intake manifold, but by an electrically controlled vacuum pump. I'm pretty sure that this is how it is on the Sorento. You should be able to verify by following the booster vacuum line and inspecting where it is affixed to at the other end. If vacuum is supplied through the intake manifold, then try racing your engine as soon as it starts (so that vacuum builds up faster) and see if the 30 second window closes up. If it does, then there's a high probability that it is indeed a vacuum leak.

  On 11/25/2015 at 3:00 PM, Rumesh88 said:

The manifold vacuum available for the brake booster is less at cold start and hence may take a little longer to build up but still it could be the sign of a small vacuum leak. There must be a small notch-like indentation on the under side of the booster body where it meets the master pump (difficult to see it from top sometimes). When the engine is cold you may temporary block the notch with something like a piece of modelling clay, chewing gum etc and test if the situation improves. However, make sure to remove whatever used to block the notch immediately for it is a safety vent which,if kept blocked could result in brake fluid being sucked into the booster. (In fact I found a KE20 booster with more than half litre of fluid accumulate inside the booster cos a maka bass had kept the notch blocked ) You may test for booster leaks as explained in this thread http://forum.autolanka.com/topic/15409-break-issue/?hl=%2Btest+%2Bthe+%2Bbooster#entry246073 or http://forum.autolanka.com/topic/15491-car-is-not-speedup-when-accelerating-bad-smell/page-2?hl=%2Btest+%2Bthe+%2Bbooster#entry247782

By the way Rumesh, this is the first time I'm hearing about the "notch" on the booster. I have in fact removed a KE20 booster, but I didn't notice this. However, I have seen boosters with a check valve.

[Rumesh88]

  Davy said:

By the way Rumesh, this is the first time I'm hearing about the "notch" on the booster. I have in fact removed a KE20 booster, but I didn't notice this. However, I have seen boosters with a check valve.

I meant this

There is a much longer notch in a KE20 booster. When there is a vacuum leak towards the master pump this notch vents out the vacuum. Otherwise unless the brake washers are in perfect condition the vacuum leak would suck fluid through the master pump into the booster.

Edited November 26, 2015 by Rumesh88