Neil F Posted February 10, 2003 Share Posted February 10, 2003 I have a 2003 Academy car and having spent a fair bit of time getting the throttle/brake position right, I was chessed off to find that the brake pedal seems to be dropping. I have only done 400 miles and first noticed the problem after I left the car standing for about 5 weeks. The brakes were sinking to about half way down and I would need to pump them to regain the height (although it wouldn't last past a couple of applications). I bled the brakes thinking it was some air shifting in the rear calipers (I hear this is a problem area) and it seemed to do the job, but having left the car another 4 weeks I find it has happened again, albeit not so pronounced this time. Needless to say i have checked for leaks (none) and checked fluid levels but I dont appear to be losing any. All I can think is that maybe the master cylinder is faulty and allowing fluid to pass one of the seals? Anyone have any ideas? Neil. Better to burn away and fade out, than to burn out and fade away.... Edited by - Neil F on 10 Feb 2003 17:45:16 Link to comment Share on other sites More sharing options...
danwhiley Posted February 10, 2003 Share Posted February 10, 2003 Neil, is this happening before, or after a bit of a blat? If before (which it sounds like from the description), it could well be that you need to do another bleed. I know that people suggest jacking up the car at one end and tapping the pipes etc while bleeding, to shift those pesky bubbles and help them "float" upwards. However, I recall hearing comments that you should lower the end which you are bleeding, due to the position of the bleed nipple on the cylinder. Can anyone else out there give Neil a definitive answer for bleeding - up, or down? Dan. p.s. Good luck with the Academy! Link to comment Share on other sites More sharing options...
F355GTS Posted February 10, 2003 Share Posted February 10, 2003 Does sound like air, somewhere, If you are not losing fluid level then I'd guess the Master cylinder is OK Mark Link to comment Share on other sites More sharing options...
TomBerlin Posted February 11, 2003 Share Posted February 11, 2003 Neil, Master cylinders can get soft without leaking. Have bled an awful lot of brake systems and have never heard of having to either lift one end of the car or tap the lines. If you're not having an assistant pump the pedal while you bleed (a self bleeding tool or trying to gravity bleed) you may not be forcing the fluid through fast and firmly enough to bring the air with it. There is no substitute for having two people do this job. It is also posible to gently clamp the rubber hoses to isolate the offending caliper or wheel cylinder. If as you imply the brakes worked initially, since air won't enter the system on it's own, I suspect the master. And yes they can be bad out of the box. Good luck Link to comment Share on other sites More sharing options...
allen Posted February 11, 2003 Share Posted February 11, 2003 I believe the sierra calipers fitted to the de dion rear, are not fitted in the original orientation, i.e. the bleed nipples are not situated at the highest point. and it can be impossible to bleed the air pocket through. I only have this second hand as I have a live axle 😬, with drum brakes allen Edited by - allen on 11 Feb 2003 02:26:44 Link to comment Share on other sites More sharing options...
JAG Posted February 11, 2003 Share Posted February 11, 2003 Guys, these rear calipers are difficult to bleed properly. You need to; 1) remove the caliper mounting bolts and bleed the caliper with the caliper held to get the bleedscrew at the highest point, 2) once bled, pump the brake pedal until the rear caliper piston is fully out (carefully! you don't want it to pop out) - then push it back in. You will need a special tool to get the piston back in, you can get one from Halfords. 3) Repeat 1) & 2) at least three times, the more the better. The main reason for all this messing about is the internal mechanism that applies the handbrake and adjusts for pad wear etc... It is extremely complex and contains a big spring, a cage to hold said spring, cams etc... basically loads of places for air to get trapped. Justin Edited by - JAG on 11 Feb 2003 09:22:48 Link to comment Share on other sites More sharing options...
prs Posted February 11, 2003 Share Posted February 11, 2003 I have these calipers on the back of my 3Dr Cossie, the position of them is pretty much the same as a caterham, however to bleed the system on the cossie you open the nipple and press down the brake pedal and then switch on the ignition whilst holding down the pedal. This activates the ABS pump and the fluid is powered through the rear calipers, it takes 10 secounds for each side to bleed clean. It comes as no surprise to me that they are a pain to bleed on a Caterham, I have partially pushed the caliper out when bleeding as this allows greater flow of fluid but you will need the specaial wind back tool afterwards. Hope this helps. Phil 😬 Link to comment Share on other sites More sharing options...
catflap Posted February 11, 2003 Share Posted February 11, 2003 Hi-spec are making a replacement for the sierra brakes, due to the amount of people having trouble Pics can be seen here (its the prototype) www.thekitcarworkshop.co.uk I have had soooo much trouble with mine, I am waiting for these to come out, I have hi specs on the fronts and they are ace Hope this helps The tips on bleeding above helped my brake feel, i blocked off the rear brake pipes and my brakeing feel went rock hard :) so i know (in my case) its the backs causing the trouble Link to comment Share on other sites More sharing options...
Neil F Posted February 14, 2003 Author Share Posted February 14, 2003 Thanks for the ideas guys. I hadn't thought of isolating the various calipers to see if there is a problem in one or (two) of them. I have a brake hose clamp but will it damage the braiding? I've also heard that some people do a modification wherby they put a thin washer between the ball and socket at the back of the master cylinder pushrod. This is supposed to take up the initial pedal slack by advancing the position of the blanking section of the piston that isolates the reservoir from the pressure circuit. Anyone got any experience of this? It sounds like I need to work on those rear callipers, I'll try them tomorrow. Neil. Better to burn away and fade out, than to burn out and fade away.... Link to comment Share on other sites More sharing options...
Peter Carmichael Posted February 14, 2003 Share Posted February 14, 2003 DO NOT CLAMP THE HOSES That was bad advice. Link to comment Share on other sites More sharing options...
neilsjuke Posted February 14, 2003 Share Posted February 14, 2003 Whilst bleeding move the hand brake on and off to shift the air . Link to comment Share on other sites More sharing options...
Neil F Posted February 15, 2003 Author Share Posted February 15, 2003 I took the car out for a drive today to really get to grips with these brakes. I didn't bleed them or anything (I wanted to see if they degraded further, which they didn't) and I did over 100 miles of country lanes and twisties. This takes the total for the car to over 500 miles (service time!) and my conclusion is that the brakes are pants. Unless I can get some air out of them or improve the pedal travel in some way I will be seriously concerned about the integrity of the brakes while racing the car. I just don't have the confidence to drive the car fast up to a corner! I understand from the Academy regulators that you can upgrade the brakes and I intend to ask how much I can do to them. Anyone got any pad suggestions; Mintex 1144s, Pagid? Neil. Better to burn away and fade out, than to burn out and fade away.... Edited by - Neil F on 16 Feb 2003 13:17:33 Link to comment Share on other sites More sharing options...
Neil F Posted February 18, 2003 Author Share Posted February 18, 2003 OK. I have now bled the brakes to death. I tapped the rear calipers, I jacked the rear up, I wiggled the handbrake (well my assistant did), we bled the rears with the handbrake on, with it off and the same again twice. I now have a firm pedal pressure.... I have also "advanced" the master cylinder piston a little to remove some of the play at the initial stroke of the pedal. The car now stops better with a positive pressure but I feel like I would have to stand on the brakes to lock the wheels. I do understand that the brakes may now bed in better and things might improve but I would still welcome suggestions for a more aggressive pad (and some part numbers if possible). I have confirmation from the Academy regulators that can upgrade the pads so I'm not being naughty! Can anyone help? Neil. Better to burn away and fade out, than to burn out and fade away.... Link to comment Share on other sites More sharing options...
MikeW Posted February 18, 2003 Share Posted February 18, 2003 Neil, Glad you got the brake bleading sorted out. When I first got mine (1600 VX Graduate) I also felt as if you really needed to stamp on the brakes. But I think it's a combination of no servo assist, no diving of front end ( that you get in a 'normal' car) and also they do take a little time to warm up. Running in the Academy you will be on the CR322's so I wouldn't go too aggressive with the pads. I use the 'green stuff' ones in mine which work fine. MikeW 1600 VX Black/Ali Membership No 6582 Link to comment Share on other sites More sharing options...
charlie_pank Posted February 18, 2003 Share Posted February 18, 2003 Neil, there's been lots of discussion on here in the last month or so about the quality of the brakes on the 7. I think that the outcome was that you don't feel like you're braking hard because a) the harnesses stop you from having to hold yourself off the steering wheel b) the front doesn't dive c) there's no servo assistance The best suggestion I read was to try a "brake comp" where you pick the adversary of your choice, and a nice straight bit of road with a conveniently placed lamp-post, agree a speed, then see who can start braking at the lamp post and stop in the shortest distance. Personally I think the stoppers are fantastic and I have an academy car with mintex pads, it's just a different feel from stopping a tin-top. Charlie'n'Kermit The plan is: there is no plan S5EVN Link to comment Share on other sites More sharing options...
Sheds Moderator Posted February 19, 2003 Share Posted February 19, 2003 My 7 brakes feel odd after a tintop, I think it's the lack of servo. Also mine is ex race and may have pads which are poor when cold, I dunno. I may try the EBC green stuff jobs come spring. Certainly some soft pads would be a good idea in a 7 to increase the feel, and it is so light that the wear would be bearable. Maybe you just need to readjust to a no-servo system and educate yourself into PRESSING the pedal rather than just taking up the slack. It always takes me a couple of applications to adjust. Link to comment Share on other sites More sharing options...
Foxy Smith Posted February 20, 2003 Share Posted February 20, 2003 Just read the following in the Caterham owners manual. "De Deon cars fitted with new pads may seem to have excessive pedal travel despite being fully and properly bled, this being due to the high mechanical advantage of the pedal. In use however, the system will improve dramatically within a few miles as the pads bed to the discs." So that's all right then! Link to comment Share on other sites More sharing options...
Neil F Posted February 20, 2003 Author Share Posted February 20, 2003 Well spotted! I hadn't seen that and it wasn't mentioned when I called Caterham... I have done 500 miles now though and I'd hoped they would have been some way to being bedded in by now? Mind you as they weren't properly bled that may affect the bedding process (I knew a girl like that once) . I'll get me coat. Neil. Better to burn away and fade out, than to burn out and fade away.... Edited by - Neil F on 20 Feb 2003 18:08:38 Link to comment Share on other sites More sharing options...
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