Hughy

Ok, here's what's happened, I was driving the car on Sunday and when I pushed the brake pedal there was nothing, it went straight to the floor, as soon as it came back up and I pushed it again they worked. This happened 4 times randomly in the 60 mile journey, I was not pushing the car and now I think about it, this only happened when I was rolling to a stop and only applied gentle pressure. I have had the brakes checked today, and the garage could find nothing wrong with them, no leaks and no fluid lost. With no visible signs of anything out the ordinary we decided to bleed the brakes for piece of mind. On the way home (about 30 miles) I stopped at the local garage, no problems on the way home until I left the garage and again was coming to a stop at the lights and applied gentle pressure to the brakes and again nothing. I know this is a long shot, but has anyone heard of this before or any idea what could be causing this,

The car is a 2011 STI Saloon and well maintained, it has alcon brakes front and rear and they are in very good condition, the front calliper's where removed around 6 months ago and re-sprayed while I had new discs and pads fitted.

Any help or advise on this would be greatly appreciated

Cheers

Hugh

joz8968

iTrader: (13)

I had an Integrale Evo I back in 1997/8, and the same thing happened to me...out of nowhere!

Luckily, I was trickling along in slow moving traffic at the time and didn't hit the car in front. (Makes me shudder to this day, thinking what might have been, if I'd been hooning at the time!)

Had it rectified at John Whalley... But for the life of me, cannot recall what was wrong/changed. I think they simply replaced the master cylinder, IIRC.

If there's no fluid leaks down by the calipers, then there must be some kind of pressure being vented somewhere, under the specific conditions you cite.

I reckon, therefore, like my situation, the master cylinder is the most likely culprit..

1509joe

iTrader: (2)

Check your wheel bearings back the pads off the discs before you check.

Don Clark

Could be your brake booster not working.

You haven't been changing hoses for silicone recently?? (missing nrv)

Brake booster checks

Hughy

Thanks for the replies guy's, I will get them things checked out......

Cheers

Hugh

360ste

iTrader: (1)

On a clear bit of road accelerate then brake immediately if the pedal travel is long come off the brakes for a second or two and try the brakes again. If you then have brakes it will most likely be the Non-Return Valve in the flexi pipe from the manifold to the brake booster. Had this when I put samco hoses on and did not know about the NRV.

1509joe

iTrader: (2)

If it was the NRV he would have a pedal and brakes albeit very hard. The pedal wouldn't go to the floor.

johned

Any leaks.

Hughy

Thanks for all the replies guy's, I have found a leak on the drivers side calliper where the pipe screws into the bottom of the calliper, could this be the problem??

Cheers

Hugh

Don Clark

The link pipe connecting the two sides together ??, then yes could be your problem.
How much fluid left in your master cylinder??

just in case it's needed
https://www.rosssport.com/Brands/ALC...ALCPSC4497X661

JDM_Stig

iTrader: (3)

Worrying the garage didnt spot it then

Hughy

Cheers Don, will get it checked to see if I need to order one....

Hughy

Very worrying, would this leak show when bleeding the brakes with the engine off..???

Godspeed Brakes

iTrader: (259)

If the pipe seems to be leaking , nip it up with a spanner , if its only leaking very slightly , it won't need tightening much , get someone holding the brake pedal on and look at the caliper to see if you can see it drip.
I'd be surprised if that was your issue though , it would have to be leaking quite a bit to lose the pedal , and then your pedal would drop everytime you pressed it.
As already been said , play in a wheel bearing can cause the pedal to drop due to pad knock off , but then it would do it quite a lot , probably everytime you turned and straightened up.
It's more likely a master cylinder , have you had the brakes bled recently ? As this can finish off a worn cylinder causes it to stop holding pressure
Hope this helps
Cheers Ian

Jonny Cut Corners

Could be a combination of problems.
Leaky line to that caliper and any of the following guesses;
- Split in a vacuum inline to the brake booster
- Failing seal in the master cylinder
- Split in a junction or hard line somewhere out of sight

Croney

I had similar happen once after a long downhill with feet off pedals in gear engine pulling vacuum for a couple of minutes which is probs longest for me (gradually slowing down long steep hill) i seemed to loose brake assist, rock hard wooden pedal. Only happened once and i Could not replicate it. I was worried for a while whst would happen if it happened at speed but it never has

1509joe

iTrader: (2)

Now that could of been your NRV stuck or possibly PCV not closing off boost.

Hughy

I have tightened the leaking line to the caliper , I will drive it for a week or so to see if it happens again or hopefully see if its sorted. Thanks for all your comments and advise...

Cheers

Hugh