[Jeroen]

Originally Posted by IndigoXLGrandDi

In our Xylo E8 ABS Nov 2009 that has covered 2,68,700+kms, I was draining the old brake fluid at wheel end and by mistake I injected air in the brake system.



Now the brake pedal is sinking down when I press the brake pedal. But it returns to its default position after its released. The braking power has reduced drastically. I got the brake system bleeding done but no improvement.



If I pump the brake pedal 3-4 times during brake application (car in motion), the brakes get applied. Even at speed of 90-100kph, 3-4 Times pumping does the trick.

Has the master Cylinder conked off?

I have got the Master Cylinder replaced around 2-2.5 years and 50-60000kms ago.

Mods please move to appropriate thread If need be.

It sounds like you still have air in the system and you need to bleed it properly before taking any further steps.
I should not drive the car in this state at all. Fix the brakes properly first thing.

Jeroen

[saket77]

^ Or there is a leak in the system. The brake pedal sinking when pressed and held is a classic symptom of leakage in the brake circuit. Advise to get it fixed as soon as possible.

[IndigoXLGrandDi]

Originally Posted by Jeroen

It sounds like you still have air in the system and you need to bleed it properly before taking any further steps.

How to conclude that the air got removed completely after bleeding the brake system?

Originally Posted by saket77

^ Or there is a leak in the system. The brake pedal sinking when pressed and held is a classic symptom of leakage in the brake circuit.

But the brake fluid level does not drop. I did a 320km trip (Sorry the Trip was unavoidable and I had to take Xylo itself in that condition). But still the Low Brake Fluid Warning was not triggered. I did not visually check the level.

The Handbrake is working Fine. The car does not move on an incline with handbrake applied.

Edit:-
Google Baba says that If the Brake Pedal is sinking down that means Master Cylinder is not able to develop and maintain Pressure.
Any idea?

[SunnyBoi]

Originally Posted by IndigoXLGrandDi

In our Xylo E8 ABS Nov 2009 that has covered 2,68,700+kms, I was draining the old brake fluid at wheel end and by mistake I injected air in the brake system.

Originally Posted by IndigoXLGrandDi

How to conclude that the air got removed completely after bleeding the brake system?.

When I was bleeding my Cedia, air always crept up in the system despite my best efforts. It seemed that air was sneaking in through the threads of the bleed nipple. The solution was to remove the bleed nipple, wrap it in 3-4 layers of Yellow Teflon tape ( Yellow is important, it is meant for uses involving oil - Avoid white tape, its meant for use with water only) like so. Replace the nipple and the leaks disappeared. Do not cover the hole in the bottom with tape - restrict it strictly to the threaded area!



Slave Cylinder with teflon taped nipple



I later realised that even though my system was bled, I would see air coming anyway. I realised even when I was pumping, air would get sucked in through threads and come out of the pipe, giving me the impression that the system still had air.

So I'd suggest you give the same treatment to all the bleed nipples of your vehicles first and bleed again.

Get a second person to help you, watch this video and make your helper watch it too so that both understand the process. One man bleeding like I mentioned in this thread is difficult to get right first time and if you're facing problems, this is perhaps the best way to tackle it.

https://www.youtube.com/watch?v=-1wmAZN2qzM

Instead of using a tube and putting it into a bottle, hook it upto a 40cm long transparent line and a 50ml syringe. Fill the pipe (syringe must be empty, press syringe all the way, dip the pipe into brake fluid and pull back the syringe so that the pipe is fill, but the syringe is still empty) then fix it to the bleed nipple.

Start the bleed process as per the video. With every press, the fluid moves ~ 30cm in the pipe. Observe the pipe if any tiny air bubbles are present. If yes, keep bleeding till you don't observe any air. When the syringe is almost full, remove it from the pipe, dump the fluid into the spent fluid bottle fix it back and continue to bleed.

You can see tiny air bubbles in the pipe



Bleeding by using these tips should help you get an air-free system. If the problem still persists, either some seal in your system is bust and is taking air - this can be piston seals in any caliper/wheel cylinders or master cylinder or ABS unit.

I made the mistake of not filling the reservoir while bleeding and managed to fill the whole system with air. With the two person bleeding, it took me 10 minutes to remove all the air and return it back to normal.

Originally Posted by IndigoXLGrandDi

The Handbrake is working Fine. The car does not move on an incline with handbrake applied.

Handbrake is independent of brake hydraulics, that is why its called emergency brakes. They work using cables and will work even if primary hydraulic brakes fail completely.

All the best!

[Jeroen]

Originally Posted by IndigoXLGrandDi

How to conclude that the air got removed completely after bleeding the brake system?

You have to make sure that only brake fluid comes out of each bleed valve no air bubbles.

As you seem to have let air in the system, you have to pump a lot of fluid through. Bit of pain, but follow the instructions in the video and you should be good to go.

I don’t know if you can get these sort of “easy bleed” sets in India. I use them all the time. Much saver, easier and quicker then pumping the brake pedal.

https://www.youtube.com/watch?v=UoCV6JSxzH0

Originally Posted by IndigoXLGrandDi

But the brake fluid level does not drop. I did a 320km trip (Sorry the Trip was unavoidable and I had to take Xylo itself in that condition). But still the Low Brake Fluid Warning was not triggered. I did not visually check the level.

If the master cilinder has developed an internal leak the brake fluid level remains steady. The best way to test is to pump the brake pedal a few times and then press on it with all your might and hold for thirty seconds or so. If it doesn’t budge you should be ok, if it slowly but surely drops you have a problem with the master cilinder, most likely a seal is broken.

Originally Posted by IndigoXLGrandDi

The Handbrake is working Fine. The car does not move on an incline with handbrake applied.

As pointed out, handbrake works mechanically and is completely independent of the hydraulic system

Originally Posted by IndigoXLGrandDi

Google Baba says that If the Brake Pedal is sinking down that means Master Cylinder is not able to develop and maintain Pressure.
Any idea?

See above. You need to distinguish between it dropping because of air or dropping because of a problem with the master cilinder

Good luck
Jeroen

[IndigoXLGrandDi]

I got the Master Cylinder replaced with New one and bleed the brake system. Now the brakes are normal.

Thank you for helping me.

[heysac]

Question: When I bleed the brake fluid of a Swift P K-Series 2010 (35K kms total), do I also need to bleed the clutch fluid separately? I got the brake fluid bleeding done 2 years/~16K kms ago. Planning to get the brake bleeding done again but read about clutch bleeding and am curious. The gear shifting is not perfect and I have been wondering whether it is an issue with clutch plates. Thanks!

[rajathv8]

Originally Posted by Jeroen

You have to make sure that only brake fluid comes out of each bleed valve no air bubbles.

I removed some brake fluid from the reservoir since the service center had filled it above the max level. Two weeks later I realized that I did not close the reservoir cap tight enough. There may have been a gap. The car was not used in this period. Is the brake fluid hygroscopic? Do I need to worry about moisture entering the system? If yes, should I get the brake system bled?

[Jeroen]

Originally Posted by rajathv8

I removed some brake fluid from the reservoir since the service center had filled it above the max level. Two weeks later I realized that I did not close the reservoir cap tight enough. There may have been a gap. The car was not used in this period. Is the brake fluid hygroscopic? Do I need to worry about moisture entering the system? If yes, should I get the brake system bled?

No worries. Yes, brake fluid is hydroscopic. But if you look closely you should be able to see a small pin hole in the cap. It is open to the air.

So it is really not making any difference. You are good to go.
Jeroen

[a4anurag]

Originally Posted by rajathv8

Is the brake fluid hygroscopic? Do I need to worry about moisture entering the system? If yes, should I get the brake system bled?

Yes, brake fluid is hygroscopic.

You can change the fluid that is contained in the reservoir with a fresh one if you are worried.

[Jeroen]

Originally Posted by a4anurag

Yes, brake fluid is hygroscopic.

You can change the fluid that is contained in the reservoir with a fresh one if you are worried.

The reservoir is open to the air, so it wont make any difference!

[rajathv8]

Originally Posted by Jeroen

But if you look closely you should be able to see a small pin hole in the cap. It is open to the air.

Thanks guys. I couldn't find any hole though. The black dots are dirt. I tried poking it just to check. There are no holes on the sides of the cap either.

[Jeroen]

Originally Posted by rajathv8

Thanks guys. I couldn't find any hole though. The black dots are dirt. I tried poking it just to check. There are no holes on the sides of the cap either.
]

Trust me, the cap is open to the air. In your case probably along the seal. As your brake pads wear down, more fluid finds its way from the reservoir to the callipers. Also, check your owner manual. It will stipulate to refresh the brake fluid every two years for this very reason.

Yours was open, sort of, for two weeks. It is a very slow process. Rule of thumb if you open a bottle of brake fluid use it within six months.

You are good to go, no worries.

Jeroen

[saket77]

I would like to share my thoughts, which is that Jeroen is right when he says there is a tiny hole on the brake fluid reservoir. But in my opinion, that hole sucks in air to enable expansion of the diaphragm gasket on the cap which pops down with fall in the brake fluid level over time.

Though, even if you left the cap open, I wouldn't be too worried. If you feel that braking efficiency is compromised, you may opt for a change; else I really wouldn't worry too much about it.

Regards,
Saket

[rajathv8]

Thanks guys. I will take your word. I do not plan to bleed the system for now. Performance has not been affected.
Out of curiosity what would happen if the brake fluid is well above the max mark?