Technical Weird and scaring brake problem...

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Technical Weird and scaring brake problem...

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Feb 4, 2011
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Just when I thought I've seen everything with this car, it keeps surpising me...

In two occasions this week, I had problem braking while driving in very low speed. The pedal got soft and the brakes seemed to have lost power. Releasing the pedal and pressing again did the trick and the car stopped without further problems.
First thing on my mind was that I must have a leak of fluid etc but here's where the fun part starts...
Having the car still on a even road I tried to reproduce the problem. It seems than when I apply very small pressure on the gas pedal ( I mean really small, like just touching it with my foot) and immediately step on the brake, the brake pedal gets soft and gets to the floor. Could not reproduce that all the time, but enough times to make me really worried. I then tried to break hard on various occasions without the just-touching-the-gas-pedal-first thing (I mean no gas or on hard acceleration) and the brakes worked as they should all the time.
Of course I will take the car for a brake check, relying on my gf's trusty Seicento until then. But does anyone have any idea what could cause such behaviour? Considering that the car is well serviced I don't think that it has something to do with the brakes themselves as the problem is not constant but happens under a certain scenario. I am suspecting some stupid electronic ESP-ish Fiat thing here. Any thoughts?
 
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I'll second that. I've had a similar problem in the past in my rally Escort on an event. Now that was worrisome!
 
Had similar issue in a BMW 323is MSPORT... about 5 years ago.
Master cylinder was replaced and was fine, also - the brakes where spongy and non existent and then 100% on so caused the car to lock up... very worrying as there was no in between, brakes either on or off and locking up when on.
 
I think the chaps above have nailed it.


I'd also make sure you change and bleed through new brake fluid to all 4 corners too.


Brake fluid should be replaced approx. every 5 years (but never is...) and if the system isn't sealed it'll allow moisture or even air in which will ruin the fluid anyway.
 
Thanx for your answers. Of course I will get the brakes checked although this has been done last summer when I changed the brake fluid and bleed the system also.
The thing that worries me most is that I think that this is not a mechanical issue with the brake system, considering that it happens at certain conditions and it's some kind of electronic issue that can happen anytime.
Thanx again, I'll let you know with the outcome...
 
definetly sounds mechanical, if the seals are leaking past on the master cylinder you will get exactly what you have described. if it was an abs your dash would probably be lit like a xmas tree besides the abs only comes on while heavy braking and sensing loss of traction via the sensors at each wheel.
go scrappy or breakers and get another master cylinder and some fresh brake juice, not incredibly difficult to fit but less than the head ache of writing off your motor.
 
I am having problem identyfying the brake cylinder part number for my 1.6 Stilo.
My number is ZFA192000000561** and on the eper my vehicle is described as M10 V3.
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On the brakes page I get two versions are highlighted, M10(V2,V3,V13) and 392 (M1,M10,M40,M50)
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The first one M10(V2,V3,V13) gives me part number 9949298 and the info I get on the internet says that is suitable for cars without EBD
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For the second one 392 (M1,M10,M40,M50) I get part number 9949303 and googling it , it says that it's for cars with EBD
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Up till now I was sure that my car had EBD (1.6 11/2001, one of the very first ones), now I am not.

Can anyone help me plz?
 
I've checked your VIN in a later (2014) version of ePER, but it still doesn't say for definite which master cylinder is fitted to your car. It shows the same 2 part numbers for the master cylinder that you posted above, except it shows them for without or with VDC (Vehicle Directional Control) instead of EBD (Electronic Brake Distribution).

I believe that all Stilos built up to mid 2003 had VDC. Your car was built on 26th November 2001. My March 2003 Stilo has VDC. It also has a white paper label stuck on the front of the brake servo with VDC printed on it. If your car has the label and it's still readable, it may give you another clue.
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Thanx Davren!
My mechanic said that mine has VDC, and the difference is that small part at the end. (the pic is from ebay, not my cylinder... )
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The problem is that he can't find a third party one of that type so he told me to search and find one myself. He can only get me the original one from Fiat and it cost 200 euros (!!!) but he wasn't sure about the part number!!!

Which part number is with VDC, 298 or 303?

Thanx again mate!
 
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Is the pin functional or is it just there to stop people installing the wrong one? I can't imagine what its for if its functional.

It's part of a device that changes the force ratio of the master cylinder piston during emergency (panic) braking. Description from eLEARN below. Bottom diagram shows the normal master cylinder and servo for comparison.
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It's part of a device that changes the force ratio of the master cylinder piston during emergency (panic) braking. Description from eLEARN below. Bottom diagram shows the normal master cylinder and servo for comparison.
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Thanks for that, sounds like its well worth having then.
 
Finally found a used one (this kind of pump is very very hard to find) and my brakes are great again! The brake guy also skimmed my discs a bit and replaced the front pads.
Thanx for all the help guys!
 
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