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 Brake pedal going to the floor - occasionally
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| philwaters Yawn..... Location: Reading, Berkshire | Posted - 7 March 2009 19:57   
A little attention grabbing, to say the least.I first had it last Sunday on the run back from Goodwood. The brakes had been fine all day with some very spirited driving on the run there and back (was with a friend on a Fireblade). Under hard loads I didn't have any problems but when I got back to his town where we parted company, I approached a roundabout and had backed off long before due to red lights. I mealy went to brush the brakes a little and there was nothing there, foot went completely to the floor. A quick pump and they were rock solid again, thankfully I had given myself plenty of space. A little spooked I left huge gaps the rest of the way home but didn't have any problems until, again I was braking very mildly and the same thing happened. Today I spent a long time bleeding my brakes fully with some new fluid, starting with the nearside rear, then nearside front and finally the offside front. Checked all the joints for leaks and everything was dry. Repeated to ensure no more bubbles and went for a test drive. (all the old fluid was clear of bubbles by the way) Same thing - again under half decent braking the pedal is firm and the car pulls up perfectly. When I gently braked at a roundabout again the pedal went to the floor and I had no brakes until I lifted and hit them harder. I can't make the problem occur, if I try to gently brake it doesn't always do it, but I could make it happen more often than it would normally by hanging back and braking very early. So - long waffle over - any ideas as to the problem? I'm running big brakes, standard master cylinder and drums on the live rear axle (and yes I've pulled them apart and checked the slaves are not leaking - bone dry). (My gut feeling is the master cylinder seals have started to go as I presume they are the type where the harder you push the more they seal, so would fail at low pressure first) Phil Waters |
| nverona I think I just saw Arne Saknussen..... Location: French Blatting in Noellet France | Posted - 7 March 2009 20:13
Phil, assuming you didn't lose any fluid it is indeed the master sylinder rubbers. If you know how to do it you can get a repair kit, if not get a new cylinders. Don't take chances. Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here You and your seven toThe French Blatting Company Limited |
| Jason Fletcher Anyone got a sock? Location: Kenilworth | Posted - 7 March 2009 20:15
Phil I don't think it can be anything other than the master cylinder. Jason C7 8USA |
| Grubbster I think I have a serious problem Location: Gosport | Posted - 8 March 2009 9:39
Same thing happened on my old Volvo years ago - replaced teh seals in the master cylinder and all OK again. Solent Se7ens Web! |
| Molecular--Bob I ought to get out more Location: In The Lab | Posted - 8 March 2009 10:12
Mine did this and pumped the fluid out along the shaft of the cylinder and deposited it in the footwell. Take the pedal cover off and pull back the rubber boot on the cylinder shaft and see if you have fluid collected in it. |
| philwaters Yawn..... Location: Reading, Berkshire | Posted - 8 March 2009 12:35
Thanks all - Will investigate part numbers for a new seal kit (a new one is over £100  )Bob, I took the pedal box off last night as part of my leak checks - all bone dry. Phil Waters |
| Billyboy Yawn..... Location: Great White, spotted in Lancs ;-) | Posted - 8 March 2009 15:34
This was happening on a customers car many years ago - In the end it was found to be a wheel bearing failing - mmm I hear you say The wheel bearing was failing and sometimes causing the disc to be wonky - in so pushing the pistons back in the caliper, when this had taken place the first application of the brake was just filling the displaced brake fluid back up in the pistons, the bearing had started to fail about 2 days before they brought the fault to our attention. I am sure you would feel it though on a 7 if this was the case.  |
| TJG Anorak Location: Herts | Posted - 8 March 2009 17:05
I appreciate resealing master is a much cheaper option but I wouldn't even consider it. Had too many fail, not worth the risk IMHO. |
| jj48 Deity Location: East Sussex | Posted - 8 March 2009 18:16
I would never re-seal any brake component, they are your lifeline so to speak. Have always fitted new master cylinder as a lot cheaper than losing your life! Richard Sussex Swede R400 |
| Paul Deslandes Anyone got a sock? Location: Guildford ('ish) | Posted - 8 March 2009 18:17
If you're stuck I have a second hand standard M/C you can have for £25 + p&p. If you're interested I'll check its condition. It spent about six years in the car (<10k miles) and eight in a box in the garage. It was okay when it came off the car and I replaced it with a racing M/C. Paul |
| Mavic82 Anorak Location: South Leicestershrie | Posted - 8 March 2009 21:12
I would agree with Billyboy. It sounds like pad nock back to me. This can be caused by warped discs or failing wheel bearing! Typical symptoms are just what you described. Guy |
| nverona I think I just saw Arne Saknussen..... Location: French Blatting in Noellet France | Posted - 8 March 2009 23:04
As long as you know what you're doing there's no danger in replacing the seals. Someone did it to the new cylinder! Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here You and your seven toThe French Blatting Company Limited |
| myothercarsa2cv blah, blah, blah... Location: Dartford | Posted - 8 March 2009 23:06
This happens on my 2cv from time to time, found it to be the drums on the rear, where the shoes drop away from the drum, and it takes a pump to lift them up again. I sorted this by adjusting the eccentics that control the shoe rest position, don't know if you have anything similar on your drums? John _________________________ Bugsy: '82 2cv6 (Back on the road!!!  )Talloulah: '08 1.6K Classic (Grubby  ) |
| AndyBeadsworth Novice Location: Warsash | Posted - 9 March 2009 11:13
How old is the brake fluid?? I had a similar experience at a track day and expert opinion suggested the fluid might be old. It deteriorates with age rather than use. I have not been back out on the track since its been replaced but will be interested to see how much diffence it makes, or not. However I will double check the seals on the master cylinder to be safe. I did have some spillage of fluid but that was put down to an incorrectly assembled race cap. I have not had any spillage with road use since then and everything seems to be functioning correctly. Andy B JPE |
| Stationary M25 Traveller I think I just saw Arne Saknussen..... Location: Not quite over the hill, NW Kent | Posted - 9 March 2009 11:35
Indeed - old fluid will be like treacle - when bleeding new fluid through the system, it is easy to see the change in colour if you use a clear pipe on the bleed nipple. |
| Brent Chiswick I think I just saw Arne Saknussen..... Location: Looking for the next project | Posted - 9 March 2009 12:13
Guys if you read the first post, I think you will find the brake fluid is approximately 2 days old. Phil, I agree with the general consensus about the master cylinder. I had exactly the same thing happen on a tin top a few years ago and it was shagged seals that caused it. You were more fortunate than me when you suddenly had no brakes then. I ended up in the back of another 7 who very kindly acted as a buffer. Mind you, no amount of pumping would have brought my brakes back as there was no fluid left in the system on mine.(fractured pipe)  Brent (aka Arfur Nayo) Lotus Elise Probably the best hair dryer in the world! Edited by - Brent Chiswick on 9 Mar 2009 12:19:42 |
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Brake pedal going to the floor - occasionally
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