Hi, I have a nearly 12 month old F2 HSE with ~13k on the clock , mostly from easy rural driving. The car has been fantastic from the day I got it, exceeding my expectations on fuel consumption & comfort and bad weather performance. However, just this last week or so it has had dead breaks first thing after standing for 12 or more hours. I have experienced disc issues from salt and wet discs before, on other vehicles, affecting the performance till it polishes off but this is different. I have to press the break pedal very hard to get just about any effect and then within just a few rotations of the wheels they come in fine. There is no rubbing noise and I have checked the discs before setting off for signs of rust etc. I also noticed that during normal driving that the breaks appear to pump up slightly if I hold the pedal constant, as if he break assist is slowly coming in.

To confirm, the surface of the discs look fine and show no signs of damage and the pads look to have plenty on them using a small mirror, but I have yet to pull them to confirm. My 30+ years of motoring (and an engineering background) makes me feel this is more like an issue with the ABS being sluggish or not working correctly. Has anyone else had problems from cold starting?

It's booked in for the 1st service next week so I will get them to check things out then, just don't want to get stung for new parts if its not the root cause.

Thanks for any advice! Fred

When the snow was at its deepest, I ploughed my way through some deep drifts then parked up overnight. The next day I noticed poor brake efficiency with some extra pedal travel. Once warmed up, they recovered but were similar after the next cold start. Now though, without intervention, they seem to be fine. It's also had a service in between and everything checked ok. I can't offer any explanation, only empathy.


EDIT:
I posted this at the time:
http://www.freel2.com/forum/topic4922.html...efficiency
...but got no response...

Fred, I don't think it's ABS related.
The ABS system is essentially a ECU connected to a wheel sensor which is constantly looking at an exiter ring/pole wheel connected to the wheel hub or brake disc, if the brakes are applied and the wheel stops rotating it backs off the brakes but just for a fraction of a second, then re-applies them.
So what else could it be....the pads?, doubtfull with the outlaw of asbestos many years ago the pad material has got harder and so tend to wear the discs more, but if the brakes are OK after an initial worrying few seconds don't think it's these.
I had a similar issue on a Passat many years ago and it was eventually found to be related to the servo. Age and red wine don't help me remember but I'm sure there's a pipe that comes from the inlet manifold on the car to pressurize the servo, I recall that the pipe had a split in it.....maybe your problem is similar to this.
Have you tried pumping the brake pedal a few times before you actually set off - maybe worth a try.
I bit of knowledge can be dangerous so please just treat these comments as a guide

Mine doing exactly the same. Ive booked mine in for a new brake servo as its all I can think of.

Mines an 08 done 10500 k.

Just for the hell of it it couldn't be ice on the pads and/or discs after overnight could it which then rubs off after a few rotations? Only a thought don't tell me I'm stupid! Ralph
Zurmatt Silver, Diesel, Automatic, side steps, mud flaps, mats, boot liner, TomTom Start 60 installed, rubbing strips, removable Brink tow bar, after market tinted glass, front styling bar, Rear spoiler, Motorlicious tail pipe trim. Wood Company centre armrest

Ralphk wrote:

Just for the hell of it it couldn't be ice on the pads and/or discs after overnight could it which then rubs off after a few rotations? Only a thought don't tell me I'm stupid!

Mine have done it too, and i thought it may be something like that.  Don't put petrol in a diesel. They don't run well.

It's a common thing during sub zero temperatures on many cars, ones much affected than others.
Maybe we should remember the laws of phisics which told us that when air moves through a small orifice (like the ones inside a brake booster) with high speed it favors the build up of moisture/condensation. Ask any dyer which works with compressed air.
The same on your brake servos.
Just that now, with much humidity in air and below zero temperatures this will result in an ice plug over night (or after some time needed for that moisture to freeze), inside your servo booster and/or booster hoses.
So, no servo assistance until that "ice cork" is dislodged or melted.
The service guys can't do anything about it, even if you want to.
Live with it, thinking of warmer days or the heavy cars with compressed air brakes where the thing is much worse....

yes i have just had this happen in the recent snow and ice so the next day i checked the discs.Found ice formed on each disc,the temp outside was -10.A few revolutions with brake pedal applied cleared it.
Like you said its not the normal gritty sound after a frw days parked up.
SO dont panic just always apply the foot brake several times gently before gathering to much speed.

My situation was more akin to the brake servo not 'charging' since I had increased pedal travel and poor efficiency. I'm inclined to agree with Alex - it will be a likely restriction (assume ice) in the vacuum source to the servo. So, no vacuum, no servo assist until the restriction is gone (thawed).
If the servo vacuum comes off the inlet manifold then humidity would play a part in the formation of ice, but diesel engines often have a vacuum pump to 'charge' the servo?? Don't know what a FL2 has.

For both the I6 and TD4 engines, the vacuum required for brake booster operation is created by a vacuum pump mounted at the rear of the cylinder head, driven by the intake camshaft.

alex_pescaru wrote:

For both the I6 and TD4 engines, the vacuum required for brake booster operation is created by a vacuum pump mounted at the rear of the cylinder head, driven by the intake camshaft.

Correct. So what are we thinking - servo failure ? Mines intermitting, sometimes I get so much travel I hit the bottom of the pedal. Another time its ok ?

Those as old as me may remember the old Ford Sierra, I used to work for a company that issued these to engineers with a 1 ton trailer laden with tooks and spares. Around the 2 year mark (70k) the brakes would intermittantly fail, we lost several vehicles. Turned out the engine had a vacume pump that charged the servo, the valves on the vacume pump would stick, no vacume no servo.

If you were lucky you would come to the lights press the brake pedal and it would barely move, you would then go through the lights and hope that no one else was coming through. Pumping the brakes would free the valve, and it would be fine for a while.

We need to keep an eye on this. There's a possibility that there may be a design issue with either the servo or the pump in cold temperatures. I'm not one for scare-mongering but brake loss needs to be taken seriously.
If it is temp. related I would expect our colder climate colleagues to experience this more-so.

Its getting a bit warmer now and I have a max / min outdoor thermometer so I will try to see if its only happening on sub zero days. I suspect the servo is working because there is not much pedal movement with the first bit progressive till if you press far enough it goes rock solid.

I will also try just a gentle breaking for a few yards deliberately to see if that warms the discs before I need them to do any real work.

Thanks to everyone for all the input, this is a great board, glad I have joined!

 Fred

AndyT wrote:

We need to keep an eye on this. There's a possibility that there may be a design issue with either the servo or the pump in cold temperatures. I'm not one for scare-mongering but brake loss needs to be taken seriously.
If it is temp. related I would expect our colder climate colleagues to experience this more-so.