[2000rpm]

Hi Guys,

I am facing a weird behavior on my 1.6 Polo wrt braking. The symptoms are below

Behavior 1 - On some occasions, when I brake lightly while slowing from a far distance, the pedal tends to slowly go in. When I start braking, the brake bites but then to maintain the same level of braking, the pedal tends to compress more and more slowly, until a certain point.
Behavior 2 - Brake bite point is variable, sometimes lower than normal point. When this happens, if I quickly do a pump, the brake point then comes to a higher point
Behavior 3 - Brake bite point is observed to be lower (more occurrences) when the car is going downhill

More data.
1. No errors on the Dashboard.
2. Car was not in use much for last 1.5 months, only occasional start-up, as I had broken my foot.

Diagnosis
Diagnosis 1 - Master cylinder failure.
Diagnosis 2 - Air in the line. I have bleed all the brakes and will see the behaviour for a couple of days of low running. If the problem does not get solved we will replace the master cylinder.

Any views by experts here??

[vrprabhu]

How does the brake pedal feel when you depress it when the car is switched off? Normally, it should become hard after three or four presses. If there are leaks, the pedal will allow to be pressed without becoming hard (which seems probable, from your description).

Have you checked the break fluid level in the reservoir? Is it level kept as prescribed in the manual? (low fluid level is an indication of leak)

[2000rpm]

The brake behaves normally.

The reservoir is topped up after bleeding.

[SS-Traveller]

Your brake booster is leaking. It's usually a sealed unit, and will need to be replaced.

[PrasadS]

Originally Posted by SS-Traveller

Your brake booster is leaking. It's usually a sealed unit, and will need to be replaced.

How can we check for leak?
My Rapid has a very sloppy bite. It just rolls ahead instead of stopping at the point i anticipate. The pads and disks show a good amount of life left. Feels like I'm using drums Instead of discs at the front.

[Jeroen]

I agree with Ss-Traveller. Sounds like the booster or a problem in the vacuum system.

Try this simple test. With the engine switched off press the brake pedal several times. The pedal should go hard and sits up high. With your foot on the brake pedal, start the engine. You should feel the brake pedal going down quite a bit.

If it doesn't it's the booster or something wrong with the vacuum.

Another possibility; one or more brake hoses has split on the inside. This happens on older hoses. It won't leak, the split is on the inside, but because of the split/tear, there is a larger volume inside the hydraulic system.

You can measure the vacuum, if you have a vacuum gauge. Check the check valve and vacuum hoses. If ok, I would replace the brake booster and if that doesn't solve the problem, replace the brake lines.

Good luck.
Jeroen

[Jaggu]

Originally Posted by SS-Traveller

Your brake booster is leaking. It's usually a sealed unit, and will need to be replaced.

Originally Posted by Jeroen

Try this simple test. With the engine switched off press the brake pedal several times. The pedal should go hard and sits up high. With your foot on the brake pedal, start the engine. You should feel the brake pedal going down quite a bit.

If it doesn't it's the booster or something wrong with the vacuum.

Another possibility; one or more brake hoses has split on the inside. This happens on older hoses. It won't leak, the split is on the inside, but because of the split/tear, there is a larger volume inside the hydraulic system.

You can measure the vacuum, if you have a vacuum gauge. Check the check valve and vacuum hoses. If ok, I would replace the brake booster and if that doesn't solve the problem, replace the brake lines.

You got your answers here ^ Do a complete check up of brake system including brake bleed, check for leaks, brake / master cylinder and vacuum efficiency. With the symptoms you described, am leaning towards an air lock / weak hoses. Even a worn out or weak hose can cause issues if they bulge when pressure is applied. Hope the fluid levels are intact?

This is a simple system so any competent dealer or non dealer garage can sort this.

[2000rpm]

Originally Posted by Jeroen

Try this simple test. With the engine switched off press the brake pedal several times. The pedal should go hard and sits up high. With your foot on the brake pedal, start the engine. You should feel the brake pedal going down quite a bit.

This behaviour is as expected.

After bleeding all 4 brakes, the behaviour seems to have gotten better.

Will keep an eye out for a few more days.

[pgoyal1996]

Leakage in brake booster is the most probable cause.
had the same issue in my Alto, The booster was leaking internally and was not able to hold the liquid under pressure. The leak was so slow that the dirt was accumulated over the brake oil in regular runs and there were no leaks in the parking bay itself.

Pls look into this ASAP, it might prove to be fatal, for how to check, take it to your ASS.

[Roops]

Vaccum hose washer broken in Polo 2018 model

Hi all,

Glad to be posting here. I drive a 2018 polo petrol version. It’s done 58k Kms as of now. Recently, the clutch plate developed issues and needed to be replaced. Took it to the ASC on Mysuru road in Bengaluru and they said that even the flywheel and water pump with thermostat needed replacement. I agreed and it was done at 53k. But just 4 days later while I was on the road, the brake went really stiff and wouldn’t respond. This was scary as I was on a main road. Thankfully there wasn’t much traffic and I was close to my home. I called the ASC and had them come over and check. The washer of the vaccum hose from the inlet manifold has broken down. They are saying that the entire inlet manifold needs replacement and will cost 25k. But it looked to me that the breakage was probably not due to wear and tear but something had gone wrong during the previous repair. I will have the inlet manifold replaced but from a different ASC. I just wanted to hear from the experienced folks here on how they would have approached this issue. Thanks a lot.

[svsantosh]

Originally Posted by 2000rpm

Hi Guys,

I am facing a weird behavior on my 1.6 Polo wrt braking. The symptoms are below

VW Polo 1.6 (11)


Guessing from your signature/footer you have a 13 time Mumbai monsoon old German car in a Ocean city Mumbai - look for rust in the booster and you may see a minor vacuum leak somewhere.

Share some pics of the booster unit as much as possible.