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2011 Megane Brakes failing

4K views 30 replies 9 participants last post by  datostar 
#1 ·
I have had a developing problem with my brakes for the last couple of weeks, they have basically became less and less effective to the point where they barely work at all. The pedal goes right to the floor and it comes to a gradual stop, if I pump the pedal then it will stop a bit better after 4 or 5 pumps.

When I pump the pedal I can hear air escaping from somewhere, sounds somewhere around the passenger footwell. Brake pads and discs are fine, im thinking its either the servo or the master cylinder, although my understanding of servo assisted brakes is a bit vague.

Any help on testing I can do would be great.

Thanks
 
#2 ·
If you can hear air, servo has to be suspect.
And is on the passenger side.
But there are many reasons why brakes fail as you describe.
Start with the basics.
Fluid level, if low, air can get into system.. that brakes get hard with pumping suggests there may be some.
Check for leaks, each wheel, jack up and remove wheels if needed. Check for signs of fluid on or around each caliper, often spread around inside of wheel.

With engine off, operate brake pedal, a few pumps and it should get very hard, that is because the servo runs out of vacuum.
Turn engine on and pedal may drop a little, should not be a lot and brakes should feel normal. If still hard or drops a lot, gotta suspect servo.


If you are unsure, get them sorted by a decent garage/mechanic, they are all that are stopping you running into the guy in front.
 
#3 ·
Well I checked the brake fluid and its filled right to the brim (possibly too much?), no obvious leaks and the brakes are that bad that I would expect a pretty major leak. As for the pedal, it never actually becomes firm when pumping it, even with the engine off, it just stops a bit better with a few pumps.
 
#5 ·
You don't say if its petrol or diesel.


If the braking system is as it left the factory and there are no liquid leaks to be found and reservoir is full (AND WASN'T REFILLED AFTER IT WAS FOUND EMPTY):


With the engine off - Pedal MUST always be hard with engine off - while the "hear air" thing is pointing to servo I have to say its not the servo alone - the fact that the pedal goes to the floor is a sure mechanical/hydraulic issue - typically master cylinder or bulging flexible hydraulic lines are involved.

The braking system must still be able to stop the car using the pedal and only its normal range of travel - this is by safety design.
 
#10 ·
Okay so just to update, I took it to a mechanic and he bled the brakes and said it was much better although as it was under warranty he was going to change the master cylinder also as it was the most likely problem.

All was good for maybe a month then they started to go again, so today I bled the brakes myself and they are now working fine, any ideas why air keeps getting into the system? I could not bleed the right rear caliper as the bleed nut is wrung, could that be a cause?
 
#11 ·
So WHY didn't the mechanic (????) fit the correct bleeder & do the job properly?
 
#14 ·
Hi guys, I have been having this problem with my 2011 Megane for some time, there is a post about it here which ultimately didnt get to a solution.


Anyways, its now been to 2 different garages, one has replaced the master cylinder and the other replaced the discs and pads, but I still need to bleed the brakes every month. I read somewhere that a bad seal on a brake caliper might cause air buildup in the brakes, without a leak? Is this likely?

I really dont want to start replacing all the calipers one by one, but I seriously have no idea where else the air could be getting in, and the mechanics seem as baffled about it as everyone else.
 
#16 ·
Posting back on this thread from the new one.

Unlikely it's a one way leak in a caliper.
What happens to the fluid level over the month?
How are they bled and is air always present in one or more calipers?
Have any of the garage interventions tried isolating a caliper with a hose clamp to see if the pedal gets harder?
As Ours2012 mentioned there is always the ABS pump ( only thing left actually :) )
I could see air being drawn in there sooner than a magic caliper one-way leak.
 
#17 ·
The fluid level is always the same, and yea when I bleed the brakes all the caliper have some air although I am unable to bleed the right rear as the bleed screw is wrung ( and according to Renault the whole caliper then needs replaced).

Is the ABS pump as big a job as it sounds?
 
#18 ·
Sorry but this plain doesn't make sense - see my earlier comment re visible leaks ...................

If you dont have a visible leak anywhere there is simply no way you can have both a constant master cylinder fluid level as well as air being bled out every few weeks.

Re the rear caliper with a busted nipple ............... in a pinch I have in the past removed the caliper, then stuck a disk between the 2 pads and held the caliper so that the hose feeding the caliper is at the highest point ............... now bleed the caliper off the car with the caliper and feed hose held in that position USING THE ACTUAL PIPE CONNECTION ON THE CALIPER TO BLEED THOUGH
 
#19 ·
Do you think being unable to bleed that caliper could be the problem? I guess there must be some air trapped in there, but when I bleed the other 3 the brakes work fine, but gradually start to go again.

As for the fluid, maybe as I am bleeding the brakes so regularly and topping up any fluid that is lost then I am just not giving it a chance to go down? That said, it is parked on a clean driveway and never shows any sign of leaks, and the 2 mechanics that have had it have found no leaks.

Idk it seems a weird problem, the mechanics I have had it with didnt really find any problems, and one other one I have spomen to reckons its the servo, although im not sure about that. Dont really know what to do, it isnt safe to drive with dodgy brakes but nobody seems able to fix it.
 
#20 ·
Servo is a vacuum so if it was playing silly, you would find your brake fluid being sucked past the master cylinder seals and you would smell it.. you would also notice brake fluid level dropping very quickly ..
Its one of the worst smells an exhaust will produce brake fluid burning and mixing with petrol or diesel fumes..
VERY RARE this happens now,, ( I have not come across it in the last 25 years, at least )


Going to have to say its down to your ABS pump failing here..

The fluid is seeping past the internal solenoids/seals so the pressure is dropping ..
 
#22 · (Edited)
As for the fluid, maybe as I am bleeding the brakes so regularly and topping up any fluid that is lost then I am just not giving it a chance to go down?
OK this is just me ...................
Whatever the cause of your dropping pedal .............. its irrelevant - you need to answer the basic question of how you can INTRODUCE NEW AIR and have a fixed level on the reservoir on a closed system while not seeing any leaks - AT ALL - EVER.

It simply doesn't matter which component puts air into the hydraulic fluid - as soon as air goes in then fluid MUST come out. You simply cannot introduce NEW air to have to bleed out of an hydraulic line without the reservoir level changing.

The ABS pump,if that is to blame for introducing air, simply cannot have a magic black hole where the brake-fluid disappears into so as to hide the fluid

There is something you are not telling us............... are you in fact seeing air coming out of the bleeding nipples with every bleed session you reckon that removes air from the system to restore imporved brake pedal feel/response?

Before you start spending big money you have to find an answer to this very basic question because there are no components on the vehicle that can hide a fluid leak permanently while introducing air - including and especially the ABS pump
 
#23 ·
Well yea, as I have said before when I bleed the brakes plenty of air comes out of each caliper (except for the one with the bad bleed nipple). I dont reckon that it removes air from the system and improves braking performance, I know it does as I have done it multiple times now.

And as I also said before, its possible there is a small leak somewhere that either I or the mechanics havnt noticed, I just know that the fluid level dosent go down noticeably.

I am not suggesting that the brake fluid is going down some 'magic hole', nor is there 'something im not telling you', I just need my car sorted and nobody seems to have a clue what the problem is.
 
#24 · (Edited)
OK then, if you are sure air does come out every time you bleed then you obviously are doing the right thing to improve braking as you say .............. all I can continue to say is that air coming out means it must get in somewhere - and more importantly since the system is supposedly sealed and has a fixed volume by design (otherwise the brakes will never work), then for new air to enter fluid MUST come out ..............I may sound like a broken record.
 
#27 ·
So just an update if anyone is still following, seems its always the one caliper that goes (near side front). When I jack it up and put the brakes on that one wheel moves freely, when I bleed it its fine again. So im gonna chance sticking a second hand caliper on it and see if it changes anything, may as well
 
#28 ·
I for one am very interested in the outcome of this little story .................

I may sound like a broken record but once again:

You cannot remove air from a caliper on a closed hydraulic system without observing either a leak somewhere or the master cylinder's level changing - really simple as that.

Its impossible that the 3 statements you make 1) you see air when you bleed and 2)no leaks anywhere and 3)no variation in master cylinder level, to all be true, all at the same time, every time.

I am going to guess and say that you are in fact NOT able to get air out of nipple when you bleed every time - or AT ALL .............. you are not going to get anywhere unless this fact is demonstrated/proven beyond doubt because there is nobody that can possibly do anything sensible about a situation like you describe. ALL of the mechanics/technicians here will confirm that and its also the reason why you're not getting any support here.............. and if its true that no air is getting bled out but rather just fluid, then as has been mentioned before the ABS is most likely the culprit

So if you think I am nuts then so be it and ignore me again, but can I suggest you actually show us with a video your bleed process where you say you find air EVERY TIME without the master cylinder reservoir level changing - try and attach a clear line to the nipple you bleed going into a clear bottle to show air bubbles you find. Make sure you show the start-off level before you start bleeding in the reservoir after you have driven around for a few days following the precise/accurate filling/noting of the reservoir level.

That vehicle must be an absolute pig to drive and a real road hazard if as you say you can apply the brake and one particular wheel will not experience any brake force at all and continue turning - this is something that can kill not only you but many others too if you suddenly need great stopping power in an emergency
 
#29 ·
Its not that im ignoring you, you just never believe me when I answer your questions, I will be sure to document the next bleeding process thoroughly for you.

I do get what you're saying, there must be a break in the system somewhere, but as there are no visible leaks I have no idea where it might be.

Changing the caliper was a bust as the replacement caliper had a ceased bleed screw, so will have to get another one and try again at some point.

The car is okay to drive as long as I bleed it regularly, its certainly not ideal but im not willing to keep taking it to mechanics for them to just keep replacing things until they find the problem, the servo and the ABS pump are both kinda pricey
 
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