[jinojohnt]

Recently when I was talking to a MASS technician, he mentioned that the brake fluid in the Master Cylinder is at constant pressure (even when car is switched off), which is bad for the Master Cylinder in the long run.
He advised me to pump the brakes 2 or 3 times after you safely park the car, so that the excess pressure in the Master Cylinder is released.
This is the first time I am hearing such a theory, is this practice good or bad? More importantly, is this another scam (to generate future repairs)?
MODS: couldn't find a related thread, pls merge/remove as appropriate.

[anandpadhye]

Wow.

Interesting.

All I can say is - if I park the Tucson for a week or so, when I get in and step on the brake paddle, it feels like a stone that would not move - untile I start the engine. This is not so pronounced in the Laura TSi or the Honda City.

Any clue why this happens?

[satyamkaushik]

Originally Posted by anandpadhye

Wow.

Interesting.

All I can say is - if I park the Tucson for a week or so, when I get in and step on the brake paddle, it feels like a stone that would not move - untile I start the engine. This is not so pronounced in the Laura TSi or the Honda City.

Any clue why this happens?

A similar thing happens to my Civic AT.

[dot]

Hardness after pumping the brake pedal when the engine is switched off is a normal phenomenon related to loss of vacuum in master cylinder. The reason for hardness on brake pedals has probably been discussed in previous threads like the following one.

http://www.team-bhp.com/forum/techni...ake-issue.html

What the SA at MASS has told could be an "old wives tale". IMO, you dont need to do such a thing after parking, the brakes system is built with this issue in mind.

Unless, of course, Maruti has a problem!

[1self]

All modern vehicles have vaccum assisted brakes. When the vaccum is not available, the brakes become hard.

However, there is a safety feature in all modern vehicles that even if the engine stops & thereby the vaccum assist is no longer available, the brakes have an 'accumulator' system whereby the vehicle would still stop a couple of times once the engine stops.

Over time, when the vehicle is not in use this accumulator system slowly 'leaks' & the brake becomes like a 'brick'!

So jinojohnt, the technician must have this in mind when he told you to pump brakes after the car is parked. However, there does'nt seem to be any sound technical reason behind this, as, when youre-start the vehicle, the accumulator is automatically pressurized.

[jinojohnt]

But if I don't release the pressure by pumping the brakes while I park overnight, it means the Master Cylinder is pressurized 24 hours a day (throughout the car's life), right? I am begining to think the SA is right.

[jav]

What you are talking about is not master cylinder but the brake booster (the round black thing) and after switching off the engine when the brakes are pumped the vacuum is used up there by making the brake pedal hard and there is now way that any of this exercise reduces or increases pressure in the "master cylinder"

Now the reason for the pedal going hard overnight can vary such as vacuum leak from the valve, rear brake shoes increased gap due to stuck adjuster etc.

[jinojohnt]

Originally Posted by jav

Now the reason for the pedal going hard overnight can vary such as vacuum leak from the valve, rear brake shoes increased gap due to stuck adjuster etc.

Does that mean that it is better to 'release the pressure by pumping the brakes' so that the valve is saved from pressure related leaks (probably because of old age)?

[jav]

the valve is a small plastic thing usually visible near the booster connected by rubber pipes on either side. now i have never heard of this going bad if the brakes are not pumped, if it was such then manufacturers would have written about it in the owners manual and i doubt that the life of valve or booster or any other brake component will actually increase by releasing vacuum by pumping the brakes IMHO.

[vikram_d]

I somehow find this logic completely wrong, because first and foremost the brake system is not a pressurised one. It becomes pressurised when you apply the brakes and even that pressure is being built by the vacuum assist and not by the brake pedals themselves.

[jinojohnt]

Originally Posted by vikram_d

I somehow find this logic completely wrong, because first and foremost the brake system is not a pressurised one. It becomes pressurised when you apply the brakes and even that pressure is being built by the vacuum assist and not by the brake pedals themselves.

But the vaccum assist is available only when the engine is running, right? When the engine is switched off, vaccum assist is available just one more time, could it mean vaccum/pressure is "stored" somewhere?

[mayankjha1806]

I do not even vaguely remember my SA at Maruti, Carnation, Tata or Honda say anything about Pump the brakes for longer life. Have never done this for last 20 years of owning self and family bought cars and in all these 20 years none of our cars had brake problems. Baleno was the first one to get its brake discs changed, In Indica and Zen we did not even change the brake discs.

So i wouldn't bother with this suggestion and continue to do the same thing, unless some new technology has come which requires me to do it.

[vikram_d]

Originally Posted by jinojohnt

But the vaccum assist is available only when the engine is running, right? When the engine is switched off, vaccum assist is available just one more time, could it mean vaccum/pressure is "stored" somewhere?

Yes vacuum assist is only available when the engine is running. There will be some amount of vacuum/pressure left over in the brake booster which allows us to be able to press the brake a couple of times before it goes hard.

I agree with Mayank, I have never followed this techinque and my cars' brakes have never given me any issues besides the normal wear and tear.

This is how vacuum assist works

Vacuum Assist
The vacuum booster on your hydraulic brake system is similar in principle to the vacuum system used in trains, varying mainly in location and power. Whereas the train system uses one or two vacuum chambers and diaphragms per axle, your car uses a single vacuum diaphragm that acts only on the master cylinder piston. This diaphragm mechanism sits in-between the brake pedal actuator rod and the master cylinder. Under normal conditions, a hose connected to the engine's intake manifold sucks all the air out of both sides of the diaphragm. When you hit the brakes, an air valve on the back of the booster opens. This difference in air pressure shoves the diaphragm forward and adds some force to the master cylinder's piston movement.

Source: How Do Vacuum Brakes Work? | eHow.com

[TaurusAl]

Are we going backward in time here ? Cars are getting more and more easier to drive and maintain and these kind of suggestions are taking me in the era of Fiats & Ambys which had too many frills before switching-off / On the vehicle or even while driving for that matter.

I agree with Mayank, We have never done it and never heard about it without experiencing any ill effects for not following this procedure, so why to introduce something new.

So dont worry, just enjoy your brakes and drive safe

[aa_asif]

As per the logic of SA, it might just extend the life of the booster (I have no clue regarding this). But at the same time, Without doing such a circus on a daily basis, your brake booster will stay strong for more than 15 years / 2 Lakhs Kms in normal Indian conditions.

What will we gain by bringing such exercise is practice? Extend the life to 25 years or 3 Lakhs?

Not worth it at all....