CC57 Posted March 17, 2010 Report Share Posted March 17, 2010 Please help. I replaced with steel, the plastic lines running to my rear brakes. I replaced them from the master cylinder all the way back the braided steel line connected to the calipers. 2 Issues: 1: Even with the bias cranked all the way to the rear I’m barely able to get a substantial amount of rear percentage. I would say I’m able to obtain about a 55 rear to 45 front split. And to get the rear higher than the front, I’m having to pump the pedal a few times (I know, not correct, uh?) 2: No fluid is leaking out any where that I can see, but if, after pumping the brakes some to get some pressure built up, if I hold the pedal steady, the gauge starts bleeding down. So it looks like: 1: I obviously still have a leak, otherwise why is the pressure bleeding down 2: Other than changing the brake line material (did not change the size), where did my rear percentage go? One guy (thanks Scooter) said I should look for pressure leaking by in the master. Maybe I must rebuild or replace the affected master. Any thoughts/suggestion/guidance? Thanks all Link to comment Share on other sites More sharing options...
Truck99 Posted March 18, 2010 Report Share Posted March 18, 2010 Sounds like you may have some residual air in the lines somewhere. Sometimes it takes quite a bit of bleeding to get all the air out when you replace lines. When you bleed the rears, crank the bias all the way to the rear. Make sure the bleeders on your calipers are all the way at 12 o'clock - take them loose from their mounts and put a spacer between the pads if that's what it takes to get the bleeder all the way to the top. Pressure bleed them rather than gravity bleeding. Good luck. Link to comment Share on other sites More sharing options...
CuttingEdgeRacing Posted March 18, 2010 Report Share Posted March 18, 2010 When you made the transition from the steel line to the braided line, did you use a -an fitting? Dont forget that AN fittings at a 37 degree flare and standard brake fittings are 45 degree flares. Sometimes people dont use the right adapter. You clearly have a leak, IMO. I had a fitting on a previous car that wouldn't leak under pressure, but would "suck back" air. Link to comment Share on other sites More sharing options...
GINGERBREADMAN Posted March 18, 2010 Report Share Posted March 18, 2010 you definately have air in system..what I find most of the time is the angle the m/c is sitting while bleeding is wrong...the end that the rod is coming out needs to be higher than the opposite end even if m/c has a bleeder...air gets trapped between the rubber boots in the m/c....I jack the car up as high as I can get it on one end while leaving other end on ground....then just bump or depress just a little bit and release...you will see bubbles coming out of the fill hole in m/c...continue till it stops bubbling...you will notice a difference in the way the pedal feels as soon as air is gone.... Link to comment Share on other sites More sharing options...
HiTech Posted March 18, 2010 Report Share Posted March 18, 2010 our cars are stock system.s and have had problems with getting air out ..pump and bleed .or gravity bleed just wasnt cutting it ...so i went to useing a hand held vacume pump ..that fixed my problems .run aboult $25.00 AT YOUR LOCAL AUTO PARTS //AUTO ZONE HAS EM OUT ON THE SHELF ....IN THE TOOL SECTION ...... TURNED OUT TO BE MY BEST FRIEND WHEN BLEEDING THE SYSTEM .. ONE MAN JOBBER ....... Link to comment Share on other sites More sharing options...
wheelchair49 Posted March 19, 2010 Report Share Posted March 19, 2010 WOW!! Look at all the professional advice you get on Lone Star Speed Zone by just asking!! Link to comment Share on other sites More sharing options...
NickHolt Posted March 19, 2010 Report Share Posted March 19, 2010 Lot's of smart, experienced guys and gals on here... Nick Link to comment Share on other sites More sharing options...
HiTech Posted March 20, 2010 Report Share Posted March 20, 2010 WOW!! Look at all the professional advice you get on Lone Star Speed Zone by just asking!! tell me how is what you said going to help this man out with his problem ..lol come on we know you know the answer .. Link to comment Share on other sites More sharing options...
thumper Posted March 20, 2010 Report Share Posted March 20, 2010 If your master cyls are floor mounted you need to add the check valves sold at most racing shops.With a floor mounted M/C the fluid will drain back to the M/C from the wheels by gravity.If I reme,ber correctly the 6 lb was for disc and the 12 pound for drum.This will stop the need to pump the brakes for pedal.If your pedals are mounted high this is no problem. Link to comment Share on other sites More sharing options...
CC57 Posted March 21, 2010 Author Report Share Posted March 21, 2010 Believe was/is probably just some air left in the system. Once I figured out how to use the Mighty Vac, I'm getting more pedal. Plus the needle on the bias gauge is holding steady. Some questions still remain though: 1) Still have the bias cranked all the way to the rear in order to get substantially more rear than front. But that may be all I should expect from a bias bar. Anyone's input on how much a bias bar will influence the differential between front and rear: 5%, 10%, 20, more? 2) Even after running a couple of cylinders worth of fluid through the lines back through the caliper bleeder and to the Might Vac cannister, I'm still seeing a somewhat steady line of very small bubles. Do you think that is just a bit of air leaking in around the bleeder valve as it's opened? 3) Still have to give the pedal a couple of pumps before the pressure gets up to where I think it should be. I just picked up some new Hawk pads. Going to install them and see if I note a difference. Don't really expect to, but it can't hurt. (I do expect to see better stopping with the Hawks compared to the worn pads I was on though.) Open to any other suggestions. And I sincerley appreciate all the input Oh yes. It's a dual reverse mount hanging master cylinder arrangement, so I as far as I know, I shouldn't have to worry about the residual valves. Link to comment Share on other sites More sharing options...
GINGERBREADMAN Posted March 21, 2010 Report Share Posted March 21, 2010 4 wheel disc or does it have drum rear??? Link to comment Share on other sites More sharing options...
CC57 Posted March 21, 2010 Author Report Share Posted March 21, 2010 4 wheel disc or does it have drum rear??? Disc at all 4 corners Link to comment Share on other sites More sharing options...
Ford27 Posted March 21, 2010 Report Share Posted March 21, 2010 I know beeding sequence is important..farthest to closest. Link to comment Share on other sites More sharing options...
Truck99 Posted March 22, 2010 Report Share Posted March 22, 2010 The pressure bias you are seeing may be related to different sized master cylinders from front to rear. If you are working on your pro truck, don't worry about getting a bunch of rear brake - you won't need it. Link to comment Share on other sites More sharing options...
97car Posted March 22, 2010 Report Share Posted March 22, 2010 I had a similiar issue with my car when I went to bleed the brakes, I also had to do a bit of cranking on the bias to get more front braking. I have 3/4 " mastercylinders, but I still have room to go, worked great the way it was before on dirt, still have good brakes on asphalt though. I would have to change a maser cylinder to change the results. Link to comment Share on other sites More sharing options...
CC57 Posted March 22, 2010 Author Report Share Posted March 22, 2010 The pressure bias you are seeing may be related to different sized master cylinders from front to rear. If you are working on your pro truck, don't worry about getting a bunch of rear brake - you won't need it. No, working on my Dirt Mod. But thanks for the truck related info. Good to know. Link to comment Share on other sites More sharing options...
GINGERBREADMAN Posted March 22, 2010 Report Share Posted March 22, 2010 on my dirt mod I had 7/8 and 1" m/c's.....7/8 on rear will get you more pressure to the rear...to adjust the brake bias correctly you should find center of adjustment.....if has 20 rounds,set at 10...depress pedal with hand or foot to apply about 20 lbs. of pressure...bias rod should run straight...if not adjust rods on m/c's till bias rod runs straight...if done right should get 60 or so front running all the way to the front and 80 plus rear adjusted all the way rear... Link to comment Share on other sites More sharing options...
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