Brakes issue

[RobKnapp2]

Hello.

Just recently a few times my 04 vrs has taken longer to stop. By that I mean that I have either had to break on the motorway, or have come off onto the sliplane, pressed the pedal, and for maybe a second, the breaks havent worked as I know they should. The first time I put it down to a little aqua planing, but the 2nd and 3rd time it is really quite scary, a 20p 50p 20p 50p job! Every time it has happened, its been raining, fairly hard, although not excessively and I havent noticed standing water. It hasnt been significantly hot, and I havent used the breaks for the last 8-10 miles. The front disks and pads will need doing fairly soon, as advised by my mechanic, although in his words "nothing to worry about for the next 5k..." however they will be getting done next month. The pedal doesnt sink, and doesnt feel spongey, although the in-voluntary reaction takes over and you press the pedal much harder than normal!

Does anyone else get this?

Is it simply water build up on the pads and disks - unlikely I would have thought given that the breaks do generate heat by driving, so I would have though they are in slight contact?

Could it be break fade? Ive never had it yet and have really hammered the breaks before and not had the slightest incling?

Could the fluid need replacing? - Will probably get it done when the disks and pads are, can only be a good thing really!

Ive only noticed this in the rain.....

Any ideas?

Many thanks

Rob

[martziniuk]

Yeah water build up on the discs.

I get it a bit on a wet morning first thing,its quite scary when i get to the bottom of my lane and the brakes don't work then suddenly anchor on.

My brakes are excellent on standard driving but when braking hard from say 120mph brake fade really takes effect and is also scary.I need to upgrade the standard brakes

[David 8]

When I was reserching the octy rs as a my next car, I found a few reviews which stated this fault iirc channel 4 cars site pointed this out. That said I've never had it happen. But it does sneek into my mind when it peeing down sometimes, maybe I have always dabbed the brakes without realising

[RobKnapp2]

Thanks for the replies people, its much appreciated. Ill keep an eye on it. To be honest, I think ive already started compensated for it by increasing the braking distance, which really does count under driving to the conditions!

Again, many thanks, its put my mind at rest, im more happy now that I dont have some form of dangerous gremlin in my car!

Cheers

Rob

[cheezemonkhai]

I would recommend a brake fluid change and if you are giving it some use DOT 5.1 rather than DOT 4.

For the sake of £50 to get it done with 5.1 and to have them check the pads/discs while bleeding the system is it really worth the risk?

[RobKnapp2]

I would recommend a brake fluid change and if you are giving it some use DOT 5.1 rather than DOT 4.

For the sake of £50 to get it done with 5.1 and to have them check the pads/discs while bleeding the system is it really worth the risk?

..I totally agree, I never skrimp on breaks or tyres. Ill get it done with the disks and pads.

Thanks.....

[VRSPhil]

I would go for super dot4 rather then 5.1. It's almost as good as 5.1 without the tiny life span.

[cheezemonkhai]

I would go for super dot4 rather then 5.1. It's almost as good as 5.1 without the tiny life span.

Super dot 4 is DOT 5.1! I think you are getting confused with DOT 5 which is totally different.

http://www.briskoda.net/forums/maintenance-performance/brake-fluids-hopefully-definitive-thread/65339/

[VRSPhil]

Super dot 4 is DOT 5.1! I think you are getting confused with DOT 5 which is totally different.

http://www.briskoda.net/forums/maintenance-performance/brake-fluids-hopefully-definitive-thread/65339/

Shell sell dot 4, super dot4 or dot 5.1....the specifications are different.

[Richy Fitt]

Audi A3's have bigger splashguards to overcome this wet weather braking problem but it has sacrificed cooling under hard driving. The A4 has FOC deflectors in Germany and these were supposed to be coming to the UK (according to Honest John). May be worth a look to see if they fit your Vrs.

[cheezemonkhai]

Shell sell dot 4, super dot4 or dot 5.1....the specifications are different.

Odd that then when you speak to the manufacturers like comma and millers and castrol they say that you have DOT 4 and then super DOT4/DOT 5.1. I specifically checked this out and run my car on DOT 5.1.

All super dot 4 or dot 5.1 are are DOT 4 type fluids with DOT 5 performance characteristics.

DOT 5 is the silicon based item which does not mix.

[KenONeill]

I'd agree with the water film theory, particularly if you have spokey alloys like I do (see avitar). The brakes don't get hot when you don't use them.

I'm presently trying to find out whether grooves or cross-drilling would be better to reduce the build-up, and let it clear faster.

Lockheed list Dot 4.0, super 4, 5 and 5.1 separately.

[cheezemonkhai]

Water on brakes bad, but I can't say it has been that noticeable on other cars I have had.

Could be that super DOT4 doesn't need to pass any tests so theirs couldl be a half way house between the 4 and the 5.1.

Either way 5.1 has a higher wet boiling point than DOT 4 so will last just as long and can mix.

[VRSPhil]

Water on brakes bad, but I can't say it has been that noticeable on other cars I have had.

Could be that super DOT4 doesn't need to pass any tests so theirs couldl be a half way house between the 4 and the 5.1.

Either way 5.1 has a higher wet boiling point than DOT 4 so will last just as long and can mix.

When I mentioned life span, I meant in terms of time between changes rather than time before boiling. 5.1 absorbs water more quickly than dot 4 so it's effectivness reduces more quickly.

[cheezemonkhai]

When I mentioned life span, I meant in terms of time between changes rather than time before boiling. 5.1 absorbs water more quickly than dot 4 so it's effectivness reduces more quickly.

As I see it DOT 5 absorbs it more quickly, but since DOT 5.1 is made from the same stuff as DOT4 it doesn't take on water any quicker. Certainly the case in my experience.

The DOT5.1 also still works at a higher temperature even when it is wet, hence shouldn't have a shorter drain life than any other fluid.

EDIT: Just to state the obvious but the Super DOT 4 and Super DOT 5 are not actually DOT standards they are just manufacturers saying that these fluids perform better than the minimum requirements for the DOT standard they are tested against in some way (Usually dry boiling point).

Understanding Brake Fluid - RPMnet.com tech articles - by AFCO racing

For example the Castrol super DOT 4 has a slightly higher dry boiling point than the minimum spec for DOT 5.1 but doesn't meet the wet boiling point for DOT 5.1

To all intents and purposes however the fluids overlap and as they are made out of the same chemical compound the take on of water will be no faster.

Silicon fluids (DOT 5) take on water much much faster than the others however.

[VRSPhil]

As I see it DOT 5 absorbs it more quickly, but since DOT 5.1 is made from the same stuff as DOT4 it doesn't take on water any quicker.

That would make sense... I don't personally know enough to argue my point, I am just repeating information from an article I read a while back in a magazine. I do take your point, but at the same time I guess there must be some difference between dot4 and dot5.1 for the boiling points to be different?

[cheezemonkhai]

I've just edeited the post above basically super DOT 4 is typically DOT 5.1 for the dry boiling and doesn't meet it for the wet boiling point.

Just whatever you do avoid the DOT 5 and either DOT 5.1 or Super 4 will work as they are essentially in the same field

[KenONeill]

The problem with DOT 5.0 (silicone) isn't how much water it absorbs how fast, but that it doesn't absorb it, so you can get bubbles of water in hot spots, with a boiling point of 100C! :eek:

[J555 JPG]

I've had this problem once in the past on a 306. Problem was eliminated by fitting Black Diamond Combi Discs(drilled & grooved)

[cheezemonkhai]

I've had this problem once in the past on a 306. Problem was eliminated by fitting Black Diamond Combi Discs(drilled & grooved)

Hello there...

Thought you might have joined up having seen you on the M27 a good few times

Yes grooved disks might help things a bit, as the water vapour will be able to escape more readily from between the friction surface.

[ScoobyChris]

I'm a mechanical numpty, but not sold on the water film on the disc theory myself as the act of rotating at a fair few revolutions should shift most water (centrifugal forces and all that). My theory would be on the relatively sheltered pad getting damp which in turn will take a few stops before it's effective again (and up to temperature). Grooved discs may be a possible solution as this will allow a passage for the water vapour to escape so the pad can still bite the disc, rather than having a layer of water vapour between the pad and the disc.

Noticed it on the Fabia with OEM brakes, but not noticed it on the Mondeo with OEM or uprated brakes. I wouldn't bother with cross-drilled personally - look nice but tend to crack and warp.

Chris

[KenONeill]

I'm not convinced by cross-drilled discs either, for much those reasons. I know pushbikes suffer similar water on friction surface problems too.

[robgraham]

Just to add my penny worth for all it is worth!

Bog standard 1.9TDi Estate - front disks and pads were replaced in the summer and I didn't notice a specific difference, apart from getting rid of a shudder on light braking. A month ago the hand brake started failing (70K miles ) and the garage had to replace both cylinders because they were leaking.

Now there was a problem because for some reason my machine is fitted with the cylinders for an automatic which are different slightly in length so when 'ordinary' cylinders were fitted the brake pedal went half way to the floor before anything happened ( anybody else met this one ?). Anyway the net outcome was that all the bleeding resulted in a change in the fluid and what a difference - might be due to having rear brakes that work but I suspect the change in working fluid was the main contributor.

Rob

[RobKnapp2]

Wow, some really interesting info on here! Thanks...

I think ill keep an eye on it, and see what happens. Being that its my only car(wife doesnt drive) our only transport, my way of making money, and I ferry the family about, im very wary of anything that isnt exactly perfect!

To this end I think ill just get the lot done, front and rear pads, fluid etc with Genuine OEM stuff. Being brakes its just not worth the risk of not doing them...

Credit card here I come....!

Thanks again for everybodys replies.

Regards

Rob

[midgebuster]

I worry about some of the stuff garages fill their customers heads with. If you are boiling dot4 brake fluid you must be driving at near competition speeds for a prolonged period. As long as your fluid is changed regularly, ie every few years there is no problem. Do these garages think that their knowledge is suddenly greater than the development engineers at Skoda? Sounds like an excuse to charge you more money. Even fluid full of water would stop you, it would just boil quicker, which is why it needs changing.

As for the wrong cylinders comment, once the brakes have been applied for the first time, the shoes will only pull back to a point controlled by the master cylinder, the length of the slave would have no effect.

I would recommend using a Skoda dealer and OEM gear. If you know your way around a car then buying genuine parts is the way to go.

My two pennys worth, I just hate to see people fleeced

Neil