Brakes going all light

[deadonkey]

Hi,

Ive been having brake related problems for a while now.

What happens is;
Say when braking under normal conditions from 60mph to a stop say at a roundabout not particually heavy but for a decently long period.
The 60 to 30ish part is great good strong direct brakes but then when the car is almost to a stop ie under 20 the brakes feel all light the braking effect on the car reduces and the pedal sinks a bit, not all the way to the floor but about an inch.

This has lead to some exciting moments, ive learned to work around the problem by releasing the pedal and reapplying the brakes.
Now ive decided it needs fixed as its not safe.

The car has done 93,000 miles and has had 2 sets of pad changes and the discs changed.
The last service at 90k i believe did not come back with any problems with the brakes.

I am wondering if they simply need bled or the fluid needs changed.
Ive always followed the 18k service intevals and had the cambelt changed at 75k.

Anyone any ideas.

 

[BrianR]

You have some serious problems there, it certainly wouldn't pass an MOT like that so do you really think you should be driving it?

It sounds like worn pads/shoes. air in the system/ system leaks/ servo not working/ poor quality brake fluid, or all of the above.

Whatever it is, I would get it fixed before your user name becomes appropriate.

 

[Ben.]

the exact same happens with mine mate...quite wierd..word to word the same as your situation!!i have also learnt the same 'technique' as you!i think mine just needs new pads tbh...but my m.o.t is soon so il let them confirm and deal with it!

its the exact same age and car as yours...except yours is alot higher miles!!

 

[deadonkey]

Its been into a dealer once about it, they changed the pads, said the discs were ok, they certainly looked Ok to me, ie no score marks etc.
It was ok for a few weeks but drifted back again.
Im thinking that its something big like a servo leaking.
Its gonna have to go back in next week

Bland : I would tell them when you take it in as mine passed an MOT with the problem, they never noticed it or it didnt show up on the brake testing rig they have.
Its strange how it does it at first I thought it was overactive ABS as instead of going all light the abs came on.

 

[BrianR]

Try this.

Engine off, hand brake off, pump the pedal until it feels hard.

Maintain the pressure on the pedal for 30 seconds or so, and check if it moves.

With your foot still on, start the engine see if the pedal comes up as the servo fills up.

 

[deadonkey]

If you pump the pedal with the engine off it gets alot harder then when you maintain the pressure it slowly sinks, ive not started the car with the pressure on yet, will try tonight.

 

[BrianR]

Try it, but from what you say, I think you have a leak on the servo.
Is the engine a bit fast on tick over ?

 

[deadonkey]

no but last week I started it from cold at work, drove out of the works car park and it just died. the engine was still running but pressing the throttle did nothing,
I turned the engine off and started it again, the first press on the throttle revved the engine but subsequent presses did nothing. after a few restarts of the engine I drove the 40 miles home no problem.

It has only happened twice in the last week and on the same day. do you think the problems are connected?

 

[BrianR]

MMMM, its not easy to diagnose like this, but I think they might be connected. Its certainly a place to start looking.

A quick simple test is to listen under the bonnet with engine running, for the faint sound of air passing through a small gap. its not conclusive but it should give you a clue if you don't have any test equipment.

 

[deadonkey]

ok, thanks for all your help. i'll have a listen
Ive had no problems up to now 93k. its gonna be one thing after another now i can see that coming.
Dealer can sort it out I'd rather pay than do

 

[dick]

93000 in 5yrs in a 1.2

jeesus

 

[deadonkey]

yeah, It's because i work 40 mile from home so without doing anything else I do 400 miles a week which ends up as over 500 so about 2k a month and 24k a year for the three years ive had this job has given me the high mileage. The engine drives just as good as it ever did tho.
ive not had any issues apart from this brake related one, its only had a new battery, pads, discs and tyres, still on the original everything else (exhaust etc)
A few years before my time I believe 100k was about the limit.

Cars have certainly improved

 

[deadonkey]

I tried starting the engine while pressing on the brake pedal, as soon as the engine starts the pedal sinks about an inch. Just the same as it would without the engine starting.

I have a feeling this is going to be expensive, I will phone my local dealer on monday to get it sorted as i'm sick of it.

 

[tidyclio]

Definetly worth changing the fluid on your mileage and age of car it should if you follow what Renault say have been changed by now.
Sounds like brake fade possibly caused by air or the fluid boiling. After a while fluid unless dot 5 absorbs moisture which turns into air when high temperatures are being generated braking from high speed.

 

[TukTuk]

it sounds like a brake servo/master cylinder fault if the brake pedal is sinkin.Couldnt diagnose the exact problem without avin a look at the car myself but at least i can give u a general idea wat the prob is

 

[Ben.]

mmm...doesnt sound good!! is this going to be an expensive job?there is a never ending list of problems with my clio..its so frustrating!! its generally when im going say 10mph and approaching a roundabout...the car feels like it doesnt want to brake even with my foot down on the pedal, but then if you lift it off and re-apply the brake, its brakes harsh?also im not sure if it is related but the brakes do squeak :S

 

[BrianR]

I tried starting the engine while pressing on the brake pedal, as soon as the engine starts the pedal sinks about an inch. Just the same as it would without the engine starting.

I have a feeling this is going to be expensive, I will phone my local dealer on monday to get it sorted as i'm sick of it.

Thats normal, if the car has been standing for a while. What you are feeling is the servo building up vacuum which has drained away while the engine wasn't ruining. Having said that, most cars will hold that vacuum overnight,at least.

If you run the engine for a few mins, then switch off and repeat the "start with your foot on the pedal" process, the pedal should just move very slightly or not at all. (sorry this is vague, I know what to look/feel for but its difficult to explain the subtle differences)

One other thought that comes to mind.

If your discs are distorted, as you drive they will push the pads back and when you apply the brakes the first push will re-align them but the pedal travel will be longer. A second application of the brakes and the pedal will not go as far.

If you have ever changed pads and forgotten to pump up the brakes, you will know the feeling, probably in your shorts.

Imagine a buckled bicycle wheel but obviously not as exaggerated.

 

[BrianR]

I was looking for something else and I came across this, it might be worth getting your dealer to check your VIN and see if its one of the cars effected, if so, get it in, its a free fix.

 

[Ben.]

^^ interesting! sounds about right, although my car is three months older than the build start date!and surely the previous owner would have realised over the 4 1/2 years of ownership??

 

[deadonkey]

Yeah im gonna book it in, It only started happening in the last 6 months, the brakes on the car were always very good.
Im going to phone and get it in this week.

 

[BrianR]

^^ interesting! sounds about right, although my car is three months older than the build start date!and surely the previous owner would have realised over the 4 1/2 years of ownership??

Not necessarily, some people just OWN cars, they don't worry about them till they stop.
Most maker recalls are recorded in the service book if the dealer remembers to write it in, best to have your VIN checked though.