I was replacing the disks and pads on Mr's Bigsurfers Vauxhall zafira last night. While doing the last wheel rushing to complete it before it got dark I forgot to open the bleed nipple before pushing the piston back. I guess I forced the brake fluid back into the master cylinder (where it overflowed). I now have a soft pedal that sinks pretty much to the floor the first time you push it but can be pumped to be fairly hard. Brakes are really rubbish only just able to stop the car. I have bleed and bleed the brakes really well, putting close to 2L of new brake fluid through the system but still no joy. I guess I have damaged something. I have read on the great tinterweb that I may have damaged the seals in the Master cylinder.
I have worked on cars for years and changed many sets of brakes on many different cars but this one has me stumped. If no body suggest anything I will have to pass it over to the garage.
I have bleed and bleed the brakes really well
No you haven't 🙂
There's air in there, you have just not found it yet.
You need to ziptie the brake pedal to the steering wheel overnight, then find a big hill and get them pads bedded in properly. Maybe..
.... remembering of course to remove the zip tie before you start the decent
What does ziptieing the brake pedal to the steering wheel do. It is definetaly not just the pads that need bedding in.
Might be air in the ABS? There is a ECU driven bleed procedure (laptop job) for this in some cases I have heard - athough...
Get on some gravel and get the ABS going nuts for a while?
Sure my Mate sorted his Passat like this
[i]What does ziptieing the brake pedal to the steering wheel do.[/i]
It's a joke; that's what people recommend for sorting out bike hydraulic brake problems.
...but you've spoiled it now.
Early Astras were notorious for this - flipping the Master Cylinder seals that is - but I've not seen it on a Zafira, so I'd start by clamping off the front brake hoses - use a proper clamp, or loads of rags wrapped around some mole grips.
Try that first and report back (mail me if you like).
Hth
Marko
Marko, I presume you mean I need to clamp of the front brake hoses while bleeding the rear brakes first. Will give it a try in the morning.
The original post describes the symptoms of flipped seals in the master cylinder.
There are no other possibilities for those symptoms, if it were my car I'd be going straight for the master cylinder - no point wasting time.
Is their anyway to flip the seals again or is it new master cylinder time.
Ooooh, I always just push the pistons back and havent had a problem, may have been lucky though.
Go to a Vauxhall/car mechanics forum for more specific advice. I'd suggest if you can find over haul kits on line for the master cylinder of your model you'll be able to dismantle it and put it back together with the seals the right way for £0.
Ooooh, I always just push the pistons back and havent had a problem, may have been lucky though.
You need to be unlucky - pushing a slave cylinder back quickly is the best way to do it, without the bleed nipple open.
The last two vehicles I've replaced pads on the destructions have just said remove sufficient fluid from the master cylinder before pushing the pistons back in, nothing about allowing the excess to exit via the bleed nipple.
Is it common to open the bleed nipple?
On some cars I open the bleed nipple, when (say) putting a jemmy between the old pads and levering the slave cylinders back in preparation for fitting new pads - because this causes high back pressure in the master cylinder.
On other cars, where a wind back tool is used, the more gradual retraction of the slave cylinder means far less chance of the master cylinder seals flipping.
Opening a bleed nipple also means you don't need to watch for an overflowing reservoir, and can catch any excessive fluid easily in a bleed bottle (presuming you have one).
i'm confused with this seal flipping thing, are you saying that by applying pressure to the brake cylinder to push the cylinder back is enough to do this?. doesn't that mean that when you press the pedal you create the same effect?. anyhoo the only time that has happened to me was on a pug 405 (rear calipers) and i eventually found that the system had a bias valve connected to the os rear wheel, this had to be under full weight load and then bled, probably not that but because the zafira is a biggish estate it may have brake biasing to take into account the possibility of heavy loads over the back brakes, sorry to be of no more help...
It is very important for cars with ABS systems to always undo the bleed valves when retracting the pistons be they straight push back or with retracting tool as contaminated fluid can be pushed back into the ABS system.
As for flipping master seals I must be honest I had never heard of that one but obviosuly it is a possibility on Vauxhalls-note to myself dont buy a vauxhall.
Rather than a strip down of the master cyclinder would a pressurised bleed kit do the job (Gunson do one that is pressured from the psi in the spare wheel and forces the fluid through from resevoir end? just a thought that it may speed the fix up.
I have the gunson one, its great. Even used it to pressurise the coolant to prove a leak to the radiator 🙂
flipping the Master Cylinder seals that is - but I've not seen it on a Zafira, so I'd start by clamping off the front brake hoses - use a proper clamp, or loads of rags wrapped around some mole grips.
spot on, same for pretty much all modern'ish cars, did the wifes fiesta the other week and the haynes manual had a 'warning box' said to do the exact same thing, just top up afterwards.
good luck, hope it sorts itself.
How are you bleeding the system ?
Modern ABS systems can have very specific bleed procedures. It often involves turning the key on and off to activate the abs valves etc.
Might be worth getting a manual or asking on a Vauxhual forum
I'd ask the guys over at VXon
[url= http://www.vauxhallownersnetwork.co.uk/forum.php ]Vauxhall Owners Network[/url]
An update:
It turns out that it is still very common to damage / flip the seals in Astra / Zafira master cylinders. If I clamp the brake hose on either of the front wheels I get a nice stiff pedal. Their seems to be quite a lot of play in the caliper on their guides as the pad engages when you push the pedal, so I guess maybe this could be the cause. Any thoughts.
<Stupid question>
If the pedal goes hard with the brake caliper isolated from the system then it presumably can't be a problem with the master cylinder?
</Stupid question>
There's supposed to be play, isn't there? Floating caliper?
But +1 for Flaperon's q.
** edited as can't be bothered repeating stuff **
1st thing, do not undo the bleed nipples to force the piston back, remove the cap and steadly puch the piston back, all you are doing is pushing the fluid back in that has gone into the lines/caliper through wear, if it overflows it means its been topped up, which you should never do unless there is a leak!!
2nd, try bedding the pads in, if the discs are worn (grooved etc..) the pedal will feel very spongy, drive for about 5 miles using the brakes as often as you can!!
3rd, if that doesn't work, then yes there is a possibility that the Master Cyl could be at fault, but not necessarily through anything you have done!!
Misinformation is now appearing on this thread.
The internet is a crap place to get advice on balance 😥
Over and out.
Surely if the brake pedal is not pushed when you wind the piston back the return port is open to the fluid reservoir and no pressure can build up to do any seal flipping ? Or am I missing something ?
Waderider, thanks for your advice, have ordered a new master cylinder, will get it fitted tonight and see how it goes.
Maybe take it to someone who [i]actually[/i] knows that they are doing and not risk killing yourself/your family/other people? Just an idea. 😉
Maybe take it to someone who actually knows that they are doing and not risk killing yourself/your family/other people? Just an idea.
Good call, there are far too many people out there who tinker with safety related items on cars, without knowing what they're actually doing!!
Maybe take it to someone who actually knows that they are doing and not risk killing yourself/your family/other people? Just an idea.
Good call, there are far too many people out there who tinker with safety related items on cars, without knowing what they're actually doing!!
Its a car not a Euro Fighter 🙂
Its a car not a Euro Fighter
Maybe so, but it illegal to work on Gas related products without the relevant certification, cars cause more deaths a year than Gas related ones, so why not?? In the wrong unqualified hands a car can be a very dangerous animal!! 🙄
Maybe so, but it illegal to work on Gas related products without the relevant certification, cars cause more deaths a year than Gas related ones, so why not?? In the wrong unqualified hands a car can be a very dangerous animal!!
They kill lots of people because people are crap at driving them not fixing them.
Do you know how many people get ill from poor handling of meats ? I think we should ban everyone except chefs from cooking chickens !!!!!
They kill lots of people because people are crap at driving them not fixing them.
And then someone fits Brakes, when thay clearly have no idea what they're doing, take it on a motorway at 70MPH plus!! Very Safe!!
And then someone fits Brakes, when thay clearly have no idea what they're doing, take it on a motorway at 70MPH plus!! Very Safe!
Thing is the OP identified there was an issue and is putting it right.I think that the issues the OP has had could quite easily have happened to a mechanic at in back street garage. All that would happen is they would have phoned him up and told him his master cylinder was faulty.
Thats some can of worms I have opened. I tend to agree with Bazzer. Despite possible how the thread has come over I have a good mechanical knowledge (and a degree in Automotive Engineering) I have been fixing my own cars for over 20 years. I know their is something wrong and was asking for advice, if I can't fix it I will obviously have to take it to a mechanic. Everybody can make a mistake and I just want to rectify it with as little financial outlay as possible.
If you are getting a firm brake pedal witht eh front brake hoses clamped off then surely the master cylinder is fine and the issue is air in the front brakes?
If you are getting a firm brake pedal witht eh front brake hoses clamped off then surely the master cylinder is fine and the issue is air in the front brakes?
That would be my thoughts.
I would pressure bleed tapping the callipers to get rid of any bubbles sticking to the side.
If it pumps up firm then my guess is its still air rather than any seal issues.
Have you actually opened any of the bleed nipples or had the reservoir empty ? If not Cant see how air has got in ?
