Brake failure

R reg 1.9 TD Fiat Ducato campervan. When we got it out of the drive yesterday the brake pedal went to the floor with hardly any braking action. Worked fine on it's last outing a few weeks ago.

On inspection, no brake fluid in reservoir (was there previously!), no obvious leaks, filling reservoir made no difference (I.e. pedal *didn't* become spongy, brakes still crap).

I'm suspecting a master cylinder problem. Does that sound reasonable? Where did the fluid go? Leaked into servo? Any idea of what it'll cost to fix?

Tim

Reply to
Tim+
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Could be the servo. Could be the rear cylinders. Have a good look around, including the drums off, see if you can see any traces anywhere.

Is it a hydraulic clutch, and does it use the same reservoir?

Do you know if the fluid's been changed every couple of years?

Reply to
Adrian

General inspection first, then pull the master cyl away from the servo.

Logically, if there is no brake fluid on the floor, nor around any wheel and no fluid in either part of the master, then it must have fallen out of the back of the master into the servo. If so then get a new master cylinder (100 quidish) suck out the fluid from the servo, refit and bleed and it should be good to go.

Reply to
Mrcheerful

That's my feeling too.

Cheers. Doesn't sound too catastrophic then. Just curious about why it should have failed, in the words of Tommy Cooper, "just like that". No warning. Working fine when last parked up. Sudden failure on next use.

Tim

Reply to
Tim+

The man from Kwikfit had a good grovel around underneath and couldn't see any signs of a leak.

I can't see a whole master cylinder reservoir of fluid leaking out without some sign. I could be wrong though.

Cable clutch.

No service history. Can't think why that would induce a sudden failure though.

Tim

Reply to
Tim+

Seal sticks to the bore, or the bore corrodes adjacent to the seal. But it'll be worth checking the rear cylinders for corrosion at the same time, given you'll need to bleed them.

Reply to
Duncan Wood

If the fluid is not changed regularly, particularly on a vehicle that is not in constant use then rust can form in the master cylinder, the rust can tear the seals and the fluid can fall out. I had a customer ask for a test on a (purely by coincidence) Renault Trafic, during the Mot the pedal gets pushed far harder than is likely on the road, after the test the pedal went to the floor on me, the seals had failed due to rust and a push too far !

Reply to
Mrcheerful

You're mixing me up with someone who still likes to get his hands dirty. ;-)

Tim

Reply to
Tim+

WEll if you don't want to get them dirty get the garage to swap the rear cylinders at the same time!

Reply to
Duncan Wood

Nice idea but I can't see why that would be cheaper than getting then done when needed as they're at the opposite end of the vehicle. Not like cam belt/water pump work etc.

Of course if the garage offers me a discount for getting work done at the same time I would consider it.

Tim

Reply to
Tim+
[...]

I think most sensible folk would be thinking 'safer', not 'cheaper'!

*If* the fault has been caused by corrosion due to lack of regular fluid changes, one or both rear wheel cylinders could fail in a similarly short period of time from 'safe' to 'dangerous'.

There would also be some cost saving in that the brakes would only need bleeding once.

Chris

Reply to
Chris Whelan

You could justify an awful lot of spending because it *might* be safer. I could replace all my brake pipe annually but would it make sense? How dangerous do you think a rear brake cylinder failure is?

They could but my gut feeling is that the fluid in the master cylinder reservoir is much more likely to absorb water than that in the wheel cylinders. Also, the wheel cylinders have a limited range of movement that will only very slowly increase as the linings wear. The master cylinder on the other hand probably experiences a bigger range of travel and has a bigger risk of encroaching on a "rust band".

I'm no expert though but you've not convinced me.

Well that's true but I think the saving would be small.

Tim

Reply to
Tim+

In the words of another great magician of Tommys time David Nixon, If you want to learn how a trick is done start at the end and work backwards.

Reply to
BigTony

Well it depends what you're doing at the time.

That's the issue, your master cylinder lives in a much more pleasant environment.

Depends on how much the cylinders cost.

Reply to
Duncan Wood
[...]

No. It would make sense to change them if there was an increased likelihood of failure, as there is in your case with rear wheel cylinders on an old vehicle with unknown history, and a current brake failure possibly caused by old fluid.

Depends to some extent on the vehicle, and the failure mode. A large, heavy vehicle that is used infrequently could have lost all the fluid in that circuit. Braking effect in those circumstances is very limited.

You are missing two important points in your theory.

1) Water collects in brake fluid over time, and it's heavier than the fluid. 2) Wheel cylinders are almost invariably positioned lower than the fluid reservoir.

The laws of gravity do the rest...

I've never subscribed to the 'only fix what's broken' method of vehicle maintenance; where things like brakes are concerned, it could be something you will regret. At the very least, as a self-confessed hater of dirty hands, surely it would be worth costing the work?

Chris

Reply to
Chris Whelan

Are you sure the man from Kwikfit didn't siphon it out whilst you weren't looking?

Let's just say that they're not the first people I'd have asked...

Did he remove the drums?

Simple. Corrosion in the bores from "wet" fluid causing rapid wear in the seals. Incredibly common.

Reply to
Adrian

Only need to bleed it all through once...

Reply to
Adrian

If all the fluid goes walkies...

Reply to
Adrian

+1 /AOL

Anyway if it's had that much water in the system the bleed nipples will be so corroded in that they will shear off.

Reply to
Peter Hill

And thus it proved to be. Master cylinder fine, brake fluid pissing out into a rear drum from a slave. I guess a free gander by the folk at Kwikfit was worth as much as I paid for it. ;-)

Tim

Reply to
Tim+

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