philwaters Posted March 7, 2009 Share Posted March 7, 2009 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 Link to comment Share on other sites More sharing options...
Normans_Ghost Posted March 7, 2009 Share Posted March 7, 2009 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 Link to comment Share on other sites More sharing options...
The Pikey Posted March 7, 2009 Share Posted March 7, 2009 Phil I don't think it can be anything other than the master cylinder. Jason C7 8USA Link to comment Share on other sites More sharing options...
Grubbster Posted March 8, 2009 Share Posted March 8, 2009 Same thing happened on my old Volvo years ago - replaced teh seals in the master cylinder and all OK again. Solent Se7ens Web! Link to comment Share on other sites More sharing options...
Molecular--Bob Posted March 8, 2009 Share Posted March 8, 2009 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. Link to comment Share on other sites More sharing options...
philwaters Posted March 8, 2009 Author Share Posted March 8, 2009 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 Link to comment Share on other sites More sharing options...
Billyboy Posted March 8, 2009 Share Posted March 8, 2009 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. Link to comment Share on other sites More sharing options...
TJG Posted March 8, 2009 Share Posted March 8, 2009 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. Link to comment Share on other sites More sharing options...
jj48 Posted March 8, 2009 Share Posted March 8, 2009 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 Link to comment Share on other sites More sharing options...
Paul Deslandes Posted March 8, 2009 Share Posted March 8, 2009 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 Link to comment Share on other sites More sharing options...
Mavic82 Posted March 8, 2009 Share Posted March 8, 2009 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 Link to comment Share on other sites More sharing options...
Normans_Ghost Posted March 8, 2009 Share Posted March 8, 2009 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 Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted March 8, 2009 Share Posted March 8, 2009 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 ) Link to comment Share on other sites More sharing options...
AndyBeadsworth Posted March 9, 2009 Share Posted March 9, 2009 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 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted March 9, 2009 Share Posted March 9, 2009 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. Link to comment Share on other sites More sharing options...
I.Mupferit Posted March 9, 2009 Share Posted March 9, 2009 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 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted March 9, 2009 Share Posted March 9, 2009 oops 😶🌫️ Link to comment Share on other sites More sharing options...
John Ryan Posted March 9, 2009 Share Posted March 9, 2009 Have you checked the temperature of the calipers after a run? I had a sticking caliper once and it caused similar issues, not sure why, but I thought it might be overheating the fluid in the caliper, hence causing fade. Link to comment Share on other sites More sharing options...
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