Sudden brake failure in mk3 VW Golf

shazzbat ( snipped-for-privacy@spamlessness.fsnet.co.uk) gurgled happily, sounding much like they were saying :

Fuck me, you'd better not ever try riding a bicycle or motorbike, then. Your tenuous grasp of basic physics'd have you off in a minute...

The front brakes do the *vast* majority of work in braking - especially on a hydraulic Cit with the front handbrake, where the rears do very little unless there's a load in the back. It's very common for the rear brake calipers to be seized because of lack of use. Free 'em up, MOT it, ignore 'em until next year.

On a CX the rear brake pads are about a quarter of the size of the fronts, and last quite literally *forever*.

Oh, absolutely. Clearly stated as "several hundred yards", probably 30 limit.

shazzbat ( snipped-for-privacy@spamlessness.fsnet.co.uk) gurgled happily, sounding much like they were saying :

And it still has to meet a certain standard of retardation to pass the MOT.

On a Golf, if the engine stops, you lose servo but still have brakes. The pedal will be heavy, but they'll work.

On a hydraulic Cit, if the engine stops, you lose the hydraulic pump and - eventually, but with a flat accumulator sphere it won't be long - steering assistance, suspension and finally ALL brakes completely. There will be NOTHING there, because the pedal isn't generating pressure as on a normal car. It's merely opening a valve to allow pressure through.

=============================== Just a thought......

I think that most cars would simply roll to a stop (when drive is removed) on the average urban road unless it happened to be a sustained slope. I think just a little bit of handbrake assistance would suffice to stop completely.

Anyone who has tried pushing a broken-down car will be aware of the difficulty of keeping it moving even on what appears to be a level road.

Cic.

IIRC If you "boil your fluid" the gas remains out of suspension and would be evident upon testing as a super-spongey pedal.

HTH

Coyoteboy ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

No, as it cools down again they go fine again.

It is now, but at one time it was also known as an emergency brake. On many modern cars it's incapable of holding a car on more than a gentle slope. As for effectively stopping a moving car, most are far too inneficient. My '96 auto BMW E39 passed an MOT only a couple of weeks ago. The h/brake performance is pathetic. It can only just hold the car in 'Drive' at tickover. Mike.

Not boiled brakes then - if you actually boil the fluid it will not re- absorb the gas. If it cools down and goes fine again it was just brake fade or the rubber pipes expanding, often mistaken for boiled brakes. It takes A LOT to boil brake fluid - even with 4 year old fluid and a jammed, at 70mph, on fire, caliper I didnt experience fluid boiling with DOT3 in a citroen AX GT. Fluid boiling is the territory of rally/ race vehicles, not passenger cars IMO.

Coyoteboy ( snipped-for-privacy@hotmail.com) gurgled happily, sounding much like they were saying :

I cracked the bleed nipple open and steam came out...

Of course it will. What's the gas? Steam from heated water absorbed in old brake fluid. What happens to steam as it cools? It turns back to water. What happens to water and brake fluid? It mixes...

In my case, it was due to M25 traffic and the 4x4's brakes being 50/50 LHM and muddy water...

Well I rode both for many years, so maybe my grasp of basic physics isn't so bad according to your criteria.

Fuck me, have you read the OP, or the rest of the thread?

Yes, when the brakes are working. What we're talking about here is handbrake

*only*, remember? The OP said the footbrake wasn't working, remember? She was pulling on the handbrake, remember? In the case of the golf, the rear handbrake, feeble though it may be, is going to bring the vehicle to a halt front end first. However, on the front handbraked Citroen, the opposite applies,or will tend to.

If you read the OP's posts, and mine carefully you will see that I was referring to what she had been told, ie that applying the (rear) handbrake when the footbrake was not working at all was likely to cause a spin, which is bollocks.

Before lecturing on basic physics it would be best to master basic reading, no?

Steve

Rubbish. Rear brakes provide so little assistance under normal braking as to be virtually worthless.

shazzbat ( snipped-for-privacy@spamlessness.fsnet.co.uk) gurgled happily, sounding much like they were saying :

How'd you pass a bike test without using the front brake for the majority of braking?

One of us has...

Bollocks. You're seriously trying to claim that using front brakes only

- which is what a front handbrake does - will somehow cause the vehicle to swap ends? EVEN if it does lock the front wheels in a turn, all that'll happen is a nice bit of safe understeer into a barrier.

Have you ever heard of a handbrake turn? How'd you think that works? The handbrake is used to lock the rear wheels. If the steering is then turned, the back swings out, since there's little grip to locked wheels, so little to prevent them moving sideways.

Indeed. That'll be why I said earlier in this thread that the handbrake WON'T cause the car to spin, if you're travelling in a straight line. Yet you seem to be telling me *I* haven't read the thread...

It's not tested by retardation of turning wheels. It's tested by attempting to turn the wheels when the handbrake is applied. A bit like a parked vehicle, wouldn't you say? It's to make sure the brake can hold the vehicle on for instance a slope. It's also a very low standard compared to a service brake.

I didn't say if the engine stops, remember? I said if all braking is lost which is what the OP said happened, remember?

So the parking brake will be the only brake available, which is what I said, remember?

Steve

I did use the front brake for most braking. However, my brajkes were working. Unlik the OP's remember?

But it isn't you....

If you're lucky. However, the OP has a golf, remember?

We're not talking about a handbrake turn, remember? we're talking about a golf trying to stop by using the handbrake, remember? This is a totally different matter, and whilst the OP has not stated what speed was involved, I doubt very much if it was sufficient to come anywhere near enough to be thinking abbout handbrake turns, given that she has already had several attempts at stopping, and it is reasonable to assume her foot has been off the throttle. I also doubt if she was applying any great steering input with the one hand not using the handbrake.

Well, you certainly seem not to have grasped the point about the OP's car trying to stop. What I said was that doing so by pulling the handbrake on would not cause a spin as she had been told. Even if the car wasn't in a straight line, the rear brake even though it is not very effective, is going to cause it to 'hang' straight.

Steve

shazzbat ( snipped-for-privacy@spamlessness.fsnet.co.uk) gurgled happily, sounding much like they were saying :

So we're agreed on that, then? Great.

Shame that wasn't the bit you took exception to me questioning...

Let me remind you - I queried your assertion that a front handbrake would make the car _more_ likely to spin. To be completely accurate, I asked if that was what you meant - and you went off on one...

You've never had back brakes lock, have you? I have. A car with a very light back end where some numpty had removed a load-limiting valve from the rear brakes. On a wet roundabout. Entertaining. For "looking-through-the- side-window-in-direction-of-travel-at-artic" values of "entertaining"...

In the case of a bike, you could be right -- the rear wheel could lift off the ground and then overtake the front, if it got pushed out.

When the brakes are working, the rear end doesn't attempt to overtake the front, does it?

So _less_ braking available.

At low speed, in a straight line, yes. At high speed, with any significant amount of steering, absolutely not. Do you know what a handbrake turn is?

The opposite will indeed apply, but you've got it the wrong way round. If you manage to brake traction with the front wheels by braking too hard, the car will just keep going straight on.

No, applying the handbrake is the best way to get the car to spin, but with some care it is entirely possible to use it to gently bring the car to a stop (if it is at all effective at the speed you're going).

His reading appears to be fine. Your physics still seems to be in need of attention.

What you said was a car with a handbrake operating the front wheels was more likely to spin than a car with a handbrake operating the rear wheels. It isn't.

No, it won't reabsorb the gas and be fine, the gas will turn into a liquid as it cools and be fine. (FSVO fine, it may not quite have the same performance as unboiled fluid, I don't know).

On every MoT I've watched over the last 40 years, the wheels have been turning when the handbrake was tested - whether by driving along with a Tapley meter on the floor, or on a rolling brake tester. I know there used to be provision for testing on a 1 in 4 slope, but I've never seen reference to a 1 in 6 (or whatever) slope to test cars with dual circuit primary brakes.

I stand by that in certain circumstances, although obviously it is not relevant to this instance. I merely used it for illustration to the OP.

To be completely accurate, I asked if

Yes I have, but it's not relevant here.

I have. A car with a very

We're talking about a golf trying to stop at the lights, remember? With the service brake not working. The OP has not said that the road was dry and straight, but she has not mentioned any extreme circumstance other than the brake failure. No mention of ice or rain or bends or steep slope or high speed.

In my first post in this thread [1] I made two primary assertions. 1 That the most likely cause of the original problem was a faulty master cylinder, and 2, that her attempt to stop the car by using the handbrake was the correct thing to do in this circumstance. I stand by both. All the rest is a distraction.

[1] Timed at 1429 on my screen, just for reference.

Steve