timbo Posted February 15, 2005 Share Posted February 15, 2005 Here's one for you. I've had a ball of bother getting a firm pedal with my brakes. (frt = Hispec 4 pots, rr = std, std master c yl.) Brake pedal feel. The pedal is soft. I can push (and takes a significant push) the pedal right to the floor. It takes a lot of force but the pedal continues downwards. A strange thing happened yesterday during once such pedal application..... the pedal went extremly soft for a second as if a bleed nipple had been released and retightened. There is no air in the sys... it has been bled, various methods, on many, many occasions. There is no fluid leaks. I pressurized the pedal, left it pressurized overnight. No leaks. When driving the brakes work but the rrs will lock first under really, really forcefull brake pedal pressure. I cannot get the frts to lock at all. I have 2 suggestions. What is the likelihood of the frt seal in the master cyl not holding the pressure, allowing the fluid to bypass the seal.... thus rr bias issue and spongy pedal. The frt brake flexi hoses have a quite small diameter hole on the union into the caliper body. (smaller than the the hose ID). Should I bore this out? The basis of this argument is that the smaller bore union may restrict flow, requiring higher brake load pressure to obtain the caliper piston movement. Any thoughts guys? Emerald Isle's 1st SV 148lbft @ 6091rpm/182bhp @ 6690rpm engineered for low revs Link to comment Share on other sites More sharing options...
andy_h Posted February 15, 2005 Share Posted February 15, 2005 I've just had similar problem with mine, but then I've not tried mine out on the road yet. My pedal was hard after bleeding but went soft overnight. I consulted Blatchat and found if you have AP racing calipers these need to be taken off the dion ears and hung upright to help air escape. I did this but no change. So I left my brake pedal wedged down hard and the cap off the reservoir, and over a couple of nights it seemed to have bled itself. Now it's been two weeks and I've still got a hard pedal. Road test next. Don't forget, if you do take the calipers off, wedge some wood in to stop the pistons falling out when you press the pedal down. Hope this helps. road legal 2.0 VX race car 😬 Link to comment Share on other sites More sharing options...
Joe 90 Posted February 15, 2005 Share Posted February 15, 2005 You can't escape the basics. If the pedal slowly goes to the floor then there are only two possibilities, a leak or a knackered master cylinder. If you're really sure there's no leak, then the master is SNAFU. If the rears lock before the fronts, then your brake balance is wrong. This seems to be quite common with the standard rear disks, and can be solved by a pad change or a brake bias valve. I would solve the pedal issue first though. Don't bother with bores, IDs etc. SEP field working, not spotted in 103,100 miles. Some photos on webshots, updated 25 Jan Link to comment Share on other sites More sharing options...
Normans_Ghost Posted February 15, 2005 Share Posted February 15, 2005 second Olivers advice Norman Verona, 1989 BDR 220bhp, Mem No 2166, the full story here Link to comment Share on other sites More sharing options...
timbo Posted February 15, 2005 Author Share Posted February 15, 2005 status: I've inspected the frt hoses. The frt flexi hose have adapters fitted for caliper threaded fitment. Whats interesting is that the adapter has a insert that sleeves inside the flexi hose body. Hence the ID of the flexi hose is greater than the ID of the adpater..... the adapter is reducing the cross sectional area. Is it possible this restriction could effect the problems I have. Have spoke to Caterham... they don't do seal repair kits for the girling master cyl. Propose to contact manufacturer direct. First I'm fitting Simon Bell's master cyl off his chassis build to try. Will give it ago at the weekend. Emerald Isle's 1st SV 148lbft @ 6091rpm/182bhp @ 6690rpm engineered for low revs Link to comment Share on other sites More sharing options...
timbo Posted February 15, 2005 Author Share Posted February 15, 2005 I've just taken off the master cyl. When hold my thumb over the frt outlet (frt brake supply outlet) and push the push-rod in I appear to get significantly less pressure than when I do the same with the rr master cyl. outlet. Would need pressure guage to measure accurately. It's looking particularily like a duff master cyl. Emerald Isle's 1st SV 148lbft @ 6091rpm/182bhp @ 6690rpm engineered for low revs Link to comment Share on other sites More sharing options...
timbo Posted February 15, 2005 Author Share Posted February 15, 2005 Part no. is Girling 74660152 59FC Who is the best to talk to re repair kit or replacement master cyl.? (that is given caterham can't get repair kits) Emerald Isle's 1st SV 148lbft @ 6091rpm/182bhp @ 6690rpm engineered for low revs Link to comment Share on other sites More sharing options...
Joe 90 Posted February 16, 2005 Share Posted February 16, 2005 As you've described it, even healthy cylinders would give less pressure due to seal friction. I don't know of anywhere that you can reliably get repair kits from as I think they went obsolete some years ago ☹️ SEP field working, not spotted in 103,100 miles. Some photos on webshots, updated 25 Jan Link to comment Share on other sites More sharing options...
Jason Plato Posted February 16, 2005 Share Posted February 16, 2005 Ithink Rob Walker has a master cylinder for sale 01179 239941 Link to comment Share on other sites More sharing options...
patneale Posted February 16, 2005 Share Posted February 16, 2005 Having built two Caterhams I know the problem. Somewhere there is some air trapped. With my first build after numerous attempts to get a firm pedal, I solved the problem instantly. I went to Halfords and bought a Gunson's Eezi bleed kit, about £15, I think. It could not be more simple. You connect up a bottle which you fill with brake fluid ( about 1/2 pint) and the top cap has two pipes. one is connected to your spare tyre and the other (which has various different caps to fit on the end) you connect to the cars brake fluid filler hole instead of the normal cap. You just go round the various brake nipples in the correct order letting out the fluid and you will be amazed at the amount of bubble of air that come out. No pumping the brake pedal, just let the spare tyre pressure do the job. 1/2 pint in the bottle tops up the level as it it let out the other end. Total success on the Caterham every time and on other cars as well. No need to put off the change of fluid in the old family banger either !! Link to comment Share on other sites More sharing options...
timbo Posted February 16, 2005 Author Share Posted February 16, 2005 Pat... used that method numerous times. Emerald Isle's 1st SV 148lbft @ 6091rpm/182bhp @ 6690rpm engineered for low revs Link to comment Share on other sites More sharing options...
patneale Posted February 17, 2005 Share Posted February 17, 2005 The build manual for Feb 2003 all models says " Uprated front Brakes" ( 4 pot ) "Initially brake pedal may seem excessive despite the system being fully bled. However the system will improve as the pads bed to the discs during the first 500-1000 miles" It does not say if this is "new" or after new pads , but it would be reasonable to assume that it would also apply for a period after new pads have been fitted. If new pads have not be fitted it sounds like a master cylinder problem! Link to comment Share on other sites More sharing options...
timbo Posted February 17, 2005 Author Share Posted February 17, 2005 Rob's sending me his old master cyl, never used, for a small fee of course. I'll let you know of the outcome. Emerald Isle's 1st SV 148lbft @ 6091rpm/182bhp @ 6690rpm engineered for low revs Link to comment Share on other sites More sharing options...
Myles Posted June 9, 2005 Share Posted June 9, 2005 Didja get anywhere with this? We discussed it on tour - but I've forgotten the outcome. My pedal will go to the floor if you keep pressure on (static - it's not a 'problem' when driving - just the lack of front braking effort...) At the local meet last night, we'd started to suspect the MC and front-seal... Project Scope-Creep is live... Alcester Racing 7's Equipe - 🙆🏻™ Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
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