Temporary brake failure - advice

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bugsy
Joined: Wed 01 Apr, 2009 10:12
Posts: 47

  M roadster S50
Location: Sutton

Temporary brake failure - advice

Post by bugsy » Mon 04 Sep, 2017 10:26

Had a scary moment on Saturday night. After a 'spirited' drive I had a temporary brake failure at the bottom of my road.
My foot went to the floor and I had hardly any brakes turning into my road. It is a built up area so I was (luckily) going very slowly when it happened.

By the time I cruised up to my driveway (approx 300m later) the brakes had returned (better than ever in fact).
I can't see anything obvious - the brake fluid reservoir is at the correct level.

It's going to go into the garage straight away. I came across these articles which explain old brake fluid boiling:
http://www.liquid-levers.com/brakefailure.htm
http://www.autospeed.com/cms/article.ht ... ure&A=0781

Other than getting the brake fluid replaced, is there anything else I should ask the garage to check for?

Thx

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dazthephot
Joined: Wed 09 Apr, 2008 19:58
Posts: 121

  Z3 roadster 1.9i
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Re: Temporary brake failure - advice

Post by dazthephot » Mon 04 Sep, 2017 15:03

Hardly any brakes rather than no brakes at all.
You probably over heated your pads.
You can check the rubber hoses going into your calliper. Also your brake lines for good measure but mainly the pads for excessive wear. The fluid change will help.


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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 634

  Z3 roadster 2.2i

Re: Temporary brake failure - advice

Post by motco » Mon 04 Sep, 2017 15:46

Overheating pads will cause fade but that usually presents a hard pedal with little effect. I did a trackday with my Z and had exactly the phenomenon you describe: long, soft pedal after hard repeated braking on a circuit. It took a couple of hours to recover in my case. Change fluid and think about DOT5.1 fluid (NOT DoT5) which has a higher boiling point. Or drive more slowly!

mrscalex
Joined: Fri 13 Mar, 2015 09:14
Posts: 795

  Z3 roadster 1.9

Re: Temporary brake failure - advice

Post by mrscalex » Mon 04 Sep, 2017 16:02

I had that many years ago in an almost brand new XR3i company car. I was approaching stationary traffic at a roundabout.

I pumped the pedal repeatedly and it came back.
ImageImage
1999 Z3 1.9 Boston Green (Dimitri) - My brother's car owned from new and restored by me
2001 Z3 2.2 Topaz Blue (Trudy) - My car rebuilt from a write-off
2002 Z3 2.2 Titan Silver (Okus) - Project car waiting for a new engine
2001 Z3 2.2 Topaz Blue (Debra) - Donor car/breaker
1998 Z3 1.9 Boston Green (Allsworth) - Donor car/breaker now gone to Z3 heaven
Always happy to try and help with spares :)

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2115

  Z3 roadster 1.9

Re: Temporary brake failure - advice

Post by Del » Wed 06 Sep, 2017 11:48

My understanding is that when the pedal travels to the floor like this it is the fault of the brake fluid. I would get some top quality Dot 4 in there with a much higher boiling point i.e. Castrol React Performance - I've got this in my cars. People (unlike me :D ) who regularly get involved in "spirited driving" in BMW M and Audi RS cars, also seem to like EBC Redstuff brake pads.

http://www.ebay.co.uk/itm/Castrol-React ... 1244219291


https://ebcbrakesdirect.com/

bugsy
Joined: Wed 01 Apr, 2009 10:12
Posts: 47

  M roadster S50
Location: Sutton

Re: Temporary brake failure - advice

Post by bugsy » Wed 06 Sep, 2017 12:15

Thanks for all the advice. Have arranged for the brake fluid change and will get all pads, disks and lines/hoses checked out as well.

I already have red stuff pads with standard disks fitted (thanks to this website). No wear warnings/issues were raised at the MOT in July.

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 634

  Z3 roadster 2.2i

Re: Temporary brake failure - advice

Post by motco » Wed 06 Sep, 2017 17:10

Del wrote:
Wed 06 Sep, 2017 11:48
My understanding is that when the pedal travels to the floor like this it is the fault of the brake fluid. I would get some top quality Dot 4 in there with a much higher boiling point i.e. Castrol React Performance - I've got this in my cars. People (unlike me :D ) who regularly get involved in "spirited driving" in BMW M and Audi RS cars, also seem to like EBC Redstuff brake pads.

http://www.ebay.co.uk/itm/Castrol-React ... 1244219291


https://ebcbrakesdirect.com/
DOT5.1 is compatible and has a higher boiling point both as new (dry) and older (wet). The only thing you must NOT do is DOT5 because it is silicone fluid. Motul do a suitable one. https://www.motul.com/ca/en-us/products ... rake-fluid

zedzedthree
Joined: Fri 29 Jul, 2016 14:16
Posts: 14

  blank

Re: Temporary brake failure - advice

Post by zedzedthree » Thu 07 Sep, 2017 21:02

Some years back this happened to me in a 9 month old Volvo without warning whilst approaching a roundabout (luckily quiet with little traffic)
felt like all brake fluid had been drained but reservoir was to max line.
Pedal returned to normal but I drove very cautiously for a few weeks and again, pedal went to floor with no warning,went to Volvo service and received lots of flannel and comments like"feels ok to me,stop worrying"
Advanced driving tuition said carry out static brake pedal test before driving car which I started doing,the pedal sank so I took the car back to service and told them that car was parked at the top of their very steep slope and maybe they would check the car for me (declined to say why, but that they would find out soon enough,my 3 kids were driven about in that car !!)
Five mins later the service guy came back on foot looking as though he needed a brandy and fresh trousers.The car had gone straight over the road at the bottom.
The master cylinder has a one way flap valve in it to stop fluid returning to reservoir until pedal is on upstroke,this had malfunctioned and other than the initial cylinder bore fill of DOT4,no more fluid could be admitted.
Result-one new warranty master cylinder and a lifetime loss of confidence in even dual line brake systems.
Lots of replies above regarding cooked pads and water in fluid etc,please bear in mind that master cylinders do have a life,do malfunction and the newest Z3 is now 14 years old.
Please consider this a possible as well.

bugsy
Joined: Wed 01 Apr, 2009 10:12
Posts: 47

  M roadster S50
Location: Sutton

Re: Temporary brake failure - advice

Post by bugsy » Tue 26 Sep, 2017 15:46

Amazingly, none of us guessed the actual problem. The side of the drivers front wheel brake pad disintegrated/collapsed.
So it was new front brake pads. All the tubes were checked and the brake fluid replaced (with Dot4) and so it is all back to normal.

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 634

  Z3 roadster 2.2i

Re: Temporary brake failure - advice

Post by motco » Tue 26 Sep, 2017 17:15

So how did the braking return if the pad had broken up?

This happened to my son's Z4M Coupé

Image

bugsy
Joined: Wed 01 Apr, 2009 10:12
Posts: 47

  M roadster S50
Location: Sutton

Re: Temporary brake failure - advice

Post by bugsy » Wed 27 Sep, 2017 09:22

On my bill it said the caliper seized as well. But they said the brake liquid would have filled the gap created by the lack of pad, so the brakes would have returned. It's just I didn't have a front near side brake.

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 634

  Z3 roadster 2.2i

Re: Temporary brake failure - advice

Post by motco » Wed 27 Sep, 2017 09:37

It is possible that the caliper piston exceeded its normal travel and seized as a result. Pumping the pedal should have drawn in more fluid as it does when you've fitted new pads and have pushed the pistons back in to the cylinders. In any case you're back on the road with functioning brakes.

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