alan c Posted January 21, 2017 Share Posted January 21, 2017 I am struggling to get my brakes bled properly. Car has the up rated AP calipers front and rear, and front ones are just back from a refurb. I have pushed 1.5L through and fluid is running clear with no bubbles but the pedal is still softI have the rear ones unbolted so I can have them vertical with the bleed nipple at the top.Any others tricks I can try?Alan Link to comment Share on other sites More sharing options...
Pendennis Posted January 21, 2017 Share Posted January 21, 2017 Have you got the rears up high with bleed nipple highest point in caliper Link to comment Share on other sites More sharing options...
alan c Posted January 21, 2017 Author Share Posted January 21, 2017 HiThe fronts are vertical with two bleed nipples at top so fairly sure problem is with the rears. They are on flexible hoses so have them unbolted and I am holding them vertical with the bleed nipple at the top. I will have another go in the morning and focus on the rears holding them higher and perhaps tapping them a little.I am using the Sealy pressure system which helps a lot and if I leave the system pressurised it hold the pressure so no leaks and there are also non visible .Just got a little frustrated, tried traditional method last week and had hoped the Sealy system and taking th rears of and holding them would solve the issue. Will let frustration subside with some red and try again in the morning. Link to comment Share on other sites More sharing options...
Pendennis Posted January 21, 2017 Share Posted January 21, 2017 Get them as high as possible, I tend to cable tie them up nearly top of damper. Presume you've got something in damper between Pistons? Link to comment Share on other sites More sharing options...
7 wonders of the world Posted January 21, 2017 Share Posted January 21, 2017 When you say 'soft' are you meaning springy or does it pump up with repeated applications of the pedal?Is the fluid your using from a new sealed bottle thats been stood for a while - seen sooo many people get a new bottle of fluid and shake it before opening it as if it were ketchup! - which naturally fills it full of tiny air bubbles... Whilst under pressure gently tap the calipers, use the hammer shaft, to dislodge and tiny bubbles still clinging to the inside of the caliper Link to comment Share on other sites More sharing options...
Ivaan Posted January 22, 2017 Share Posted January 22, 2017 Have you installed new pads? In which case it could just be that they need bedding in.Does the brake peddle hold up firm with constant foot pressure on it, or does is continue to sink down? If so, then you have a problem with the master cylinder seals.Having the calipers re-furbished means that the system has been drained for some time, so the seals could suffer. Link to comment Share on other sites More sharing options...
alan c Posted January 22, 2017 Author Share Posted January 22, 2017 Thanks for the various comments, I have had another go today and not really made any progress. In answer to the various questions:-1 Fluid I am using is new and purchased in last couple of weeks so that should be ok.2 I had a brake judder issue and have already replaced front discs etc so calipers were away for a refurb to try and solve that so I have not yet got as far as trying the car on the road so newish pads not the issue. At least if so I have not got that far yet.3 if I pump the pedal and keep my foot on it there is no further movement and pedal feels firmer but not right, it does not go down even with foot on brake for some time. Take foot off and leave for a few seconds and it's soft again. So I don't think its an issue with the master cylinder.4 I had rear calipers as high as I could get them and ran about 0.5 L through them whilst tapping them. Fluid runs clear with no bubbles. (Block of wood is wedged between the pistons)Unless I am missing something it still feels like there is air in the system somewhere. Any other ideas? Link to comment Share on other sites More sharing options...
Pendennis Posted January 22, 2017 Share Posted January 22, 2017 Have you tried bleeding the brakes the old fashion way with someone in car and you on calipers?If I remember correctly on your other thread I thought It would probably be the master cylinder. I be interested to know like you what the problem is, but as I said on your other thread I had a similar situation and was convinced it was moisture then after flushing it was still there so thought it must be air, after I checked for air again and any leaks which there were none I had no choice but to change the master cylinder as it couldn't be calipers, my evidence did not justify them at fault. That was my problem, abnormal pedal travel with pressure differential feed back via pedal.Before you go and buy one have you checked for any leaks? Do you have a brake bias valve in the rear line? If yes, I presume you have it fully open at this stage? Link to comment Share on other sites More sharing options...
alan c Posted January 22, 2017 Author Share Posted January 22, 2017 HiFairly convinced the original problem was not the mater cylinder. We were able test the car at an MOT station on their rolling road and vibration/judder was only evident on the front wheels. So I assumed if it had been the cylinder it would have been evident on all wheels. Having said that I guess I cannot rule out that there is now a problem there given car was sat for about a months with no brakes.I did start with the traditional method of foot on pedal but purchased the Sealey kit so I could try and make progress on my own. I might go back to traditional approach tomorrow evening. There are no visible leaks anywhere and if I leave the system connected to the Sealy brake bleeder with 20psi of pressure it holds that.I am not aware if I have a brake bias valve and I have certainly not adjusted one. If had one where would it be and what does it look like. Link to comment Share on other sites More sharing options...
Pendennis Posted January 22, 2017 Share Posted January 22, 2017 There are many types of bias valve, but here is the CC version: https://caterhamparts.co.uk/other/2459-valve-brake-reducing-csr.htmlThey could be installed anywhere on the rear brake line, normally it's located either drivers or passenger footwell compartment near seating position. To be honest you'd know if you have one Link to comment Share on other sites More sharing options...
Pendennis Posted January 22, 2017 Share Posted January 22, 2017 I only bleed the brakes the old fashioned way, never trust the new devices! Starting left rear, then right rear, left front then right front, always bleeding furthest away nipple from MC first, so last nipple is front right nearest to MC Link to comment Share on other sites More sharing options...
alan c Posted January 22, 2017 Author Share Posted January 22, 2017 Ok I don't have a bias valve I would have spotted it in those locations. Order you set out is the order I have been following.I will persuade "boss" to help again tomorrow evening and see if going back to traditional method makes any difference. I had best put the heater in the garage for a while first though. It is an integral garage with some insulation but it has not been very warm this weekend. Link to comment Share on other sites More sharing options...
alan c Posted January 22, 2017 Author Share Posted January 22, 2017 Ok I don't have a bias valve I would have spotted it in those locations. Order you set out is the order I have been following.I will persuade "boss" to help again tomorrow evening and see if going back to traditional method makes any difference. I had best put the heater in the garage for a while first though. It is an integral garage with some insulation but it has not been very warm this weekend. Link to comment Share on other sites More sharing options...
Pendennis Posted January 22, 2017 Share Posted January 22, 2017 Yep a tad chilly, My missus hates doing it but promise her a new handbag!It's quite important to get those rear calipers up high, good luck Link to comment Share on other sites More sharing options...
elie boone Posted January 24, 2017 Share Posted January 24, 2017 I use an old reservoir cap with a hole drilled in it and pressurize it with a blow gun at 0.4 bar and never had issues bleeding except once for a faulty Sierra caliper. Link to comment Share on other sites More sharing options...
John Vine Posted January 24, 2017 Share Posted January 24, 2017 The front AP 4-pots have two nipples per calliper. Are you bleeding the inner nipple first, and then the outer?For info, the Assembly Guide says:"The uprated front brakes have two bleed screws on each calliper. Remove the dust cover from the inboard bleed screw on the front LH calliper. Connect the flexible tube to the bleed screw and operate the brake pedal several times. Whilst mounting pressure on the brake pedal open the bleed screw and allow compressed air and brake fluid to flow into the container. Tighten the bleed screw before the pedal is released. Repeat the procedure until no air bubbles are visible in the released brake fluid. Remove the flexible tube and replace the dust cap. Carry out the procedure for the outboard bleed screw."JV Link to comment Share on other sites More sharing options...
MADMALC Posted January 24, 2017 Share Posted January 24, 2017 I think you need to run the car and bed the brakes in and then do another bleed to be sure that the problem is air or indeed the master cylinder.If you have done as John has shown above then my suggestion seems the next logical step.Both 7s I have built had 'squidgy' pedals till the whole system had had some use (abuse). Link to comment Share on other sites More sharing options...
Pendennis Posted January 24, 2017 Share Posted January 24, 2017 You should never have squidgy pedals at any point either during or after assembly!!It is not that important whether you do the inner or outer bleed first or second. As a rule of thumb the motor trade normally start furthest away from MC and work their way in, but it isn't that important on ours. Link to comment Share on other sites More sharing options...
alan c Posted January 24, 2017 Author Share Posted January 24, 2017 I have tried the front calipers several times sometimes inner first and sometimes outer and it makes no difference.The pedal is so soft it is not safe to take the car on the road, it was bad enough turning the car round in the road to reverse it into the garage for easier access.Going to try traditional approach next and see what happens and it has also been suggested I leave it under pressure for several hours and see what happens. Link to comment Share on other sites More sharing options...
Pendennis Posted January 24, 2017 Share Posted January 24, 2017 Blimey, they are bad. What master cylinder you got and what fluid you using? Link to comment Share on other sites More sharing options...
Pendennis Posted January 24, 2017 Share Posted January 24, 2017 Blimey, they are bad. What master cylinder you got and what fluid you using? Link to comment Share on other sites More sharing options...
OliverSedlacek Posted January 24, 2017 Share Posted January 24, 2017 I recommend getting hold of a vacuum bleeder. After struggling using all the above suggestions, I borrowed one and got an instant result. My personal theory is that all the pressure systems compress the air bubbles and they stick in the nooks and crannies. Vacuum bleeders drag the air out with the fluid. Link to comment Share on other sites More sharing options...
elie boone Posted January 25, 2017 Share Posted January 25, 2017 Never had any problem with my system, takes about 1 h to put the 7 on axle stands drain the system refill and bleed single handed. Link to comment Share on other sites More sharing options...
MADMALC Posted January 25, 2017 Share Posted January 25, 2017 If it is so bad the only answer that seems logical is that the master cylinder is letting fluid past the main seal but the fluid is being retained by the secondary seal so no leak is showing. I would be stripping the master cylinder if it were mine, if that proves a red herring then a small fire may fix the issue! Link to comment Share on other sites More sharing options...
Pendennis Posted January 25, 2017 Share Posted January 25, 2017 You wouldn't get any leaks if the seals were worn and letting by!You just are unable to maintain pressure Link to comment Share on other sites More sharing options...
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