Brakes don't feel right
Discussion
I don't like my brakes, day to day commuting they're fine, but the few occasions when I have to slow down a bit quicker than expected they don't seem to do anything when I press a little harder. So I panic, and press harder, which causes the car to brake suddenly, emergency stop style.
The initial braking effect is normal, if I press a little harder no additional braking seems to materialise, until I press harder still, which causes the brakes to react too much, this makes me think the mechanics of pads and discs etc are OK.
I had a look while the car was at the tyre fitters and there was 5mm+ on the pads, the discs seem to look like they've 50,000 miles and should last that again.
So is this down to the fluid? The car is 6 years old, brake fluid degrades over time doesn't it?
The initial braking effect is normal, if I press a little harder no additional braking seems to materialise, until I press harder still, which causes the brakes to react too much, this makes me think the mechanics of pads and discs etc are OK.
I had a look while the car was at the tyre fitters and there was 5mm+ on the pads, the discs seem to look like they've 50,000 miles and should last that again.
So is this down to the fluid? The car is 6 years old, brake fluid degrades over time doesn't it?
As mentioned, brake fluid and hoses. Probably fluid is my guess. Two years is a reasonable change interval as it's extremely hygroscopic. As soon as I bought my camper I had the fluid replaced and the brakes improved immensely.
Also it's worth checking to see if there are any leaks.
If you're unhappy take it into a garage and explain what's going on. Brake work isn't terribly expensive (unless a caliper is sticking) and getting the fluid changed is generally very cheap. Garages have proper pressure bleeding systems which means it's a fast and easy job.
Also it's worth checking to see if there are any leaks.
If you're unhappy take it into a garage and explain what's going on. Brake work isn't terribly expensive (unless a caliper is sticking) and getting the fluid changed is generally very cheap. Garages have proper pressure bleeding systems which means it's a fast and easy job.
cuprabob said:
VW will change brake fluid for fixed price of £59
I know, but no thanks.I asked VW to fix an electric window switch which had fallen into the door once.
When it appeared they hadn't done that work I asked why I'd been billed for it, they said they did do it, but it must have fallen into the door again because the switch is broken.
No s
t sherlock.I need someone who is going to look over the brake system and use their brain to problem solve, not just replace a part (in this case, some fluid) from some bullet points on a computer monitor.
Failure of VW mechanics to apply common sense is why I won't go to them for this issue.
doogz said:
R300will said:
I'm sure water isn't compressible 
and if you do apply pressure to it it won't boil will it? unles its serious pressure. Yes?
and if you do apply pressure to it it won't boil will it? unles its serious pressure. Yes? 
Sorry, stupid typo. If you change what i wrote to incompressible, it should make more sense.
Cheers.
doogz said:
R300will said:
No probs, i thought i was going mental then
I just read it again. It made sense in my head. Like you say, water, not too compressible, so yeah, it'll generally do the job for the first couple of times you hit the pedal, until (rather quickly) the fluid heats up, water boils, steam is much more compressible, which is bad news when you want to apply pressure to the pads, or shoes.Once it absorbs the water it lowers the boiling point of the fluid - when you heat up the calipers etc under sustained heavy braking you start to get the water boiling out of the fluid. Once that starts happening you'll have problems stopping, because instead of compressing the pads to disc, you're just compressing the gas in the lines (or the low-density fluid, depending on the state)
Ledaig said:
Is now a good time to mention that both hydraulic fluid and water are compressible?
not enough to cause the issue here admittedly, but still....
well yeah but not very i would think. I remember seeing some space program, on discovery i think, which said that the oceans were so deep on a particular planet that the water at the bottom was compressed into a solid but above the melting point of water. The oceans were stupidly deep so the pressure must have been immense. not enough to cause the issue here admittedly, but still....
Had something similar on my wifes car, turned out to be faulty cylinders in the rear drums. Farily cheap to buy and an afternoons work to fit.
As has already been said it's worth changing the fluid and having the system properly bled as well as checking the brake lines and hoses for signs of deterioration.
As has already been said it's worth changing the fluid and having the system properly bled as well as checking the brake lines and hoses for signs of deterioration.
R300will said:
well yeah but not very i would think. I remember seeing some space program, on discovery i think, which said that the oceans were so deep on a particular planet that the water at the bottom was compressed into a solid but above the melting point of water. The oceans were stupidly deep so the pressure must have been immense.
Ok so a little O/T, but it's more prevalent than you think.As an example, if you had 300L of hydraulic fluid at 200Bar with a Bulk Modulus of 1.4GPa, you would actually have the equivalent of a 4.3L compression of the fluid (or more importantly in the realms of industrial hydraulics, 4.3L of fluid to decompress before you start to operate any valve etc).
As I mentioned though, for the brake's it's not an issue. The water/moisture turning to steam is a separate problem.
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