I've been having problems bleeding my rear brakes. I tried using the push on the brake pedal method but getting no where. I have a mity vac which uses vacuum. I got fluid to the passenger side rear and it's coming clear. The driver side doesn't want to bleed for some reason? Am I not bleeding it long enough. I know back brakes are a pain to bleed. I also noticed that my brake light doesn't come on either when I depress the pedal. The switch is spiced into the rear brakes line, thus telling me I still have air in the line and I don't have pressure to the switch. If I pump the brakes slightly, the brake light flickers on and off. Anybody have suggestions on what I should do next?

 

It kiind of does sound like you have an air block in the driver's side. What is your brake system configuration (not stock, I think?). The line to the driver's side could be plugged, or the bleeder screw holes could be. If there weren't caps on the bleeder, I'd bet on dirt getting in there and blocking the hole. Have you tried the mity vac on that one?

 

Ross, I tried the mit vac on the driver's side. I see fluid coming out but very little. I didn't have any blockage with the drum brakes and they worked fine. The lines are all new. The only thing I replaced was cutting the hard lines and adding the rubber hose ends with the connections to mount the line to the calipers. Maybe I should keep trying to bleed the lines? I am getting fluid coming out the bleeder and I'm showing less fluid in the MC bowl. I guess my question is, does it take several times of cracking the bleeder and bleeding the lines to get the air out of the line? If that makes sense?

 

Back to the top! I need some advice from you brake mekanics out there. HELP! LOL....

 

Just a wild thought ed, When you converted your front brakes to disc didn,t you use cpp master cylinder with built in proportioning valve? Doesn,t that have to be changed when you go from a disc drum to a disc disc? If you already took care of that just ignore me.

 

I gather that you have 4 way disk? What style calipers? And yes sometimes you must go around more than once. Back when I was turnin wrench we would seat the piston by pulling the beak line off caliper and use air-compressor to apply brakes at caliper then let up on the piston. Sometimes the piston is pushed into boar of caliper so far that bleeding is impossible. If you do this though please put on at least 3 lug nuts to square up rotor to axle. Is the system a standard split ie fronts/rears as with most rear wheel drive or diagnal split. Also if you converted from a disk/drum to a disk/disk did you change the mastercylinder. It wont change bleeding but it will change operations. Disk/drum have check valve to keep slight pressure on wheel cyl cups so they hold pressure. Kurt G. Y-blocks rule.

 

Thanks for the suggestions everyone. I have the CPP front kit, but the calipers are standard GM. My master cylinder is a Corvette which is suppose to be disc/ disc. When I had the drum in the rear (now disc brakes using the Cadillac calipers) I installed a Wilwood proprotioning valve in the line to the rear brakes. I am running separate brake lines. Front reservoir to front calipers and rear bowl to rear calipers. If I bleed the brakes using the mity vac, I've been trying it several times and still get fluid but not a clear steady stream. I'm wondering if I can have that much air in the lines? I had to replace the rear portion of the hard lines, so most of the lines were removed to install the disc brakes. How long should it take to bleed brakes effectively? I did notice that the brake fluid is still coming out dirty and not clean like the new stuff I'm adding. Should I keep bleeding the lines or maybe use another method? I'm trying to avoid taking it to a shop if I can figure this out myself.

 

I would try bleeding. How close is the drivers side pads to caliper. Do your GM caliper have the screw in pistons for adustment (Its been 15 yrs since I turned wrench for a living, things change includung my memory). Does the park brake accuation lever twist piston out when applied? Or is park brake off center of rotor on back side? Kurt G.

 

Kurt- I have the brake actuation lever that twists the piston out. I have the parking brake set with new cables and they grab the disc. The piston is in the middle of the caliper. I know these calipers are a real pain to adjust, but they have the Ebrake mechanism which others don't. I would like to have an ebrake, even if it doesn't work.... LOL.... Ed

 

Some have had a problem with the brake flexible lines having bad fittings allowing rubber to partly block fluid within the lines. Crack the line at the start of the flex line for flow.What part of the system is old possibly having dirt in it? Have a great day,chuck

 

There is no part of the brake system that is old now. Everything has been replaced. I used the mity vac again and it seems like there is still air bubbles coming out the line. The brakes have improved and now I can pump it a few times at the pedal and my brake lights work again. When it sits for a while, the pedal fades and I lose my taillights. It sounds like air in the lines, but I've been bleeding this thing just about everyway possible. Maybe I'll take it to a brake guy and have him bleed it and be done with it. This is frustrating as heck! Didn't have this problem bleeding the drum brakes at all. I don't think I bleed them but once, maybe twice. Thanks for the suggestions everyone. Any great tips on bleeding the lines?

 

Ed, could the copper washer between flex line and caliper have a scratch and allow air to get past. I'm going to ask some stupid questions but please bear with me. Have you let system set to see if fluid leak is detected. Have you ever seen a pressure bleeder? It applies 15 psi of pressure sent to hydrolic chamber pressurizing fluid to mastercyl through master cover adapter. The shop I worked at had an Ammco pressure bleeder. Maybe you can rent one if you can gain access to top of master, you need room for the adapter to fit. Kurt G.

 

Ed, sorry forgot to mention you will want to have park break cables working though. The park break is the adjustment for rear breaks, GM type rear caliper work different than front. The square cut seal on front calipers allow piston to pull back just a little after each break application resulting in front break adjustment but on rear caliper piston jas 1 way ratcheting actionand when enough pad wear happens piston stays in new location. If park break is not used the after some miles front breaks start doing mor than thier share of work causing overheated front rotors, resulting in rotor warpage. Also when changing pads on the rear you will need to screw the piston in DO NOT PRESS IT IN. Does the rear piston surface have notches on face of piston near edges? Sorry to bore you with all this. I'd hate to see a friend make a mistake that could be avoided, by the way you have a very cool lookin truck. Kurt G.

 

If you are getting bubles using the mighty vac and losing your brakes after a couple of days then you have a leak somewhere in the rear lines. Using a pressure bleeder would show which connection is leaking or undo all the connections and look for damaged threads or seats on the lines. Maybe even mismatched threads somewhere or a loose fitting. I don't know about the Vette m/c but the typical disc/drum GM m/c uses the rear port to feed the front brakes and the front port to feed the rears.
Jeff

 

Ed, if everything is new including the MC, did you bench bleed the MC? You still could have air in there if you didn't. If you have the manual proportioning valve make sure it is wide open during the bleeding process.