brakes won't bleed :(

[kelner]

So I've been wrestling with my car the last two weeks trying to figure out what happened to the brake system (more on that in a moment). The car was at my mother's and I only really get sundays to go down to her place and work on it, so really only worked on it two days total plus today. It's my only transportation and I had been borrowing her van, but had to give it back today so I am stuck driving a very scary vehicle. For reference this is a 1986.5 Toyota Supra w/o ABS.

It all started when I was just driving in some Atlanta traffic and the brake pedal went soft and I wouldn't get pressure until about 3/4 of the way to the floor. Now my brake wear indicators had been squealing at me for sometime so I thought maybe I had ignored them too damn long. So I changed them and no improvement.

Now at this point I test drove the car down the street and I could still lock the tires up and stop from reasonable speeds. I was just scared whatever was wrong would fail and I would end up in someone's ass (if you live in Atlanta you know how people drive and you know the traffic is shit. I'm sure there are plenty of other big cities just the same way).

So I decided to try bleeding the brakes even though I had not opened the lines or removed them at any point. Well I start with the back passenger since that is the furthest away from the master. It just dribbles out fluid. Maybe once every 20 times I bleed it there would be a nice stream (I had my mother on the pedal and I would get up and check the reservoir every 5 or so pumps). Both rear calipers were like this. When I moved to the front after 30 mins of trying to bleed the back I got a normal response from the bleeders. Nice long streams of fluid.

Now, I thought maybe I had some ridiculous amount of air in the system so I tried bleeding the pass rear for another 30 mins (I probably open and closed the valve at least 300 times) and finally got pissed off. So I decided to try adjusting the brake pedal height to see if I extended the master arm out some more if it would change things. No luck there either (extended it all the way out).

Now at some point I started wondering if the proportioning valve might be causing this issue some how. Everyone I talked to assured me it wasn't because it's just an iron block with different sized holes in it. So I listened to them and did the next best thing. I threw some parts at it.

I replaced the master cylinder in an attempt to get this shit working even though I had no reason to believe it was at fault. Well, my old one was dirty as shit and had crud (just looked like build up of dust and dirt inside the reservoir. No real big chunks) in it so I cleaned out the reservoir and hooked up the new MC. I attempted to bleed the rears, but I got the same thing as before, just a trickle of fluid. The fronts bled fine, but the brake pedal was softer and went event further to the floor.

Test drove it again and now couldn't lock the brakes up and the pedal feel was worse. Nobody carries a proportioning valve, I guess it's up to me to pull mine out and see if something is wrong inside? Has anyone heard of this happening?

Does anyone have ideas on what it could be? (BTW: there are no leaks or kinks anywhere in the brake system, I have checked numerous times).

Cliffs:
Brake Pedal feel changes
Change Brake pads - Feels the same
Bleed brakes - rear calipers don't want to bleed properly
Replace MC - bleed brakes, rears still won't bleed - brakes suck worse
Ideas?

 

[benchwarmer]

After you swapped the master cylinder did you bleed the rear brakes until you saw new fluid coming out?

 

[kelner]

After you swapped the master cylinder did you bleed the rear brakes until you saw new fluid coming out?

I attempted to bleed the rears, but I got the same thing as before, just a trickle of fluid. The fronts bled fine, but the brake pedal was softer and went event further to the floor.

yes I did, but after about 10-15mins of it just dribbling fluid out I gave up on them.

 

[87nasupra]

have you traced your lines and checked for dents/ crimps in line making sure they are straight? i just replaced brake lines at my job last week because the lady hit a tire from a tractor trailer on the highway and bent the LF brake line causing a soft and low pedal. Just a thought. GL

 

[Chaos_Performance]

well the first problem that i see is that the m/c was never bench bled to get the seals sitting right and the fluid in it. thats y there is a shit load of air in the system now and some will never comer out as the m/c needs to be bled seperate from the system hope this helps

 

[87nasupra]

well the first problem that i see is that the m/c was never bench bled to get the seals sitting right and the fluid in it. thats y there is a shit load of air in the system now and some will never comer out as the m/c needs to be bled seperate from the system hope this helps

It would also help if he noted the brand of MC as some of them that i use at work do not require a bench bleed. I installed mine on a ABS n/a auto that stated to bleed right off the start.

 

[gaboonviper85]

well the first problem that i see is that the m/c was never bench bled to get the seals sitting right and the fluid in it. thats y there is a shit load of air in the system now and some will never comer out as the m/c needs to be bled seperate from the system hope this helps

don't have to do this with a supra m/c....you can but it will bleed just fine....when I replaced mine I didn't tighten the braklines down tight and let fluid come out the threads then locked them down...didn't even bleed the system afterwards either and had no issues.

 

[67rstbkt]

I would always suggest bleeding a new M/C. The fact that the rears are just dribbling can't be a good sign. have you tried undoing the lines and spraying brake cleaner through them? I once had a clutch line get so clogged it would'nt bleed. I shot a can of brake cleaner through it, let dry, and then ran the brake fluid through.

 

[kelner]

Sorry I've been absent in the thread. Sorry, I did not mention that I did in fact bench bleed the MC w/ the couplers and lines that it came with.

Like I said, the problem was present long before I even went to a new MC. I have attempted bleeding several times since my last reply and the front brakes still bleed fine and I do have pedal feel back to normal (outside of the adjustment I made to the brake pedal which is causing some play at the top of the pedal travel, but I am going to readjust the pedal this weekend to the correct height). So I have had front brakes the past week and I stop just fine now and the pedal feels fine.

However, rear brakes still don't bleed. At all. I literally attempted to bleed the passenger rear for a half hour and never once did I get a stream of fluid. I gave the driver rear a shot, but I only gave it about 10 mins before I gave up on it.

I think either there is an obstruction in the hard lines or the lines have collapsed in both rears. Not sure how to tell if they are collapsed, but a visual inspection makes it appear as if they are fine.

I am going to start pulling lines this weekend and I will figure it out.

Thanks for all the ideas and help.

 

[Bill UK]

Probably blocked bleeding nipples, the hole at the bottom seals over with rust. The Toyota part # is for one only.

 

[87nasupra]

best bet is to take both rear bleeder stop out and hit the pedal. If you get fluid coming out, you know its the bleeder stop. IF not you know its something in your lines.

 

[kelner]

Well I did not get a chance to troubleshoot as much as I wanted this weekend, but I did order two speedbleeders for the rears.

After putting the speedbleeders in and mashing on the brakes a lot I still didn't get any fluid

So I took the bleeder screws out completely and still nothing. I didn't have a chance to remove the rubber lines going to the calipers though, but I have a three day weekend this weekend so I can hopefully find out what's wrong then.

I think I am going to order a ss line kit today and if worse comes to worse it's just an upgrade for me.

 

[CPT Furious]

FWIW, I had a very similar problem to you and it turned out that two reman master cylinders I got from O'Reilly's were both bad. After I went and got a brand new one from my Toyota dealership, I had no problems. I can't explain why, but a new cylinder solved my troubles when the remans couldn't...

link:

http://www.supramania.com/forums/showthread.php?t=74678

 

[kelner]

well it seems there was something wrong with the way I screwed the rear line into the MC because nothing was coming out (that is, I unhooked the lines at the caliper, metal-to-rubber connection, behind the fuel tank, at the proportioning valve and then finally at the MC) until I unscrewed it from the MC and then it pissed fluid everywhere. I really don't know what the problem was, but I unhooked it, fluid went everywhere. I hooked it back up, opened the speed bleeder on the rear passenger and it farted (most literally) all the air out and then I hear nice squirts and took a look under the car and lots of fluid was coming out.

I was so happy! My brake pedal feel is back and stopping power seems improved. My front rotors are defiantly warped, but I read some good information on how to prevent this next time. Apparently ceramic pads do not hold heat like organic and semi-metallic pads plus the addition of copper fibers help dissipate heat thus preventing the warping of rotors (warping is caused from braking, be it normal or extreme, and the brake pads heat up, as well as the rotor, but when you come to a stop the pad keeps a section of rotor hot while the rest cools off resulting in the warping). According to the text drilled/slotted rotors do next to nothing to help this and generally decrease brake performance unless using a much larger rotor and pad/caliper. Apparently they were designed originally to release gas that was caused from the friction between the pad and rotor, but thanks to advanced in technology we no longer have to worry about that.

I still have no e-brake and I really do miss it because you don't realize how often you use it until you don't have it (specifically when i want to keep the car running but want to get out of the car to do something). I might look into some sort of hydraulic solution if there is one available because I really hate the fucking drum brake design.


Thanks for all who helped!! I was really scared that the above post might have been what happened to me, but luckily it was just something screwy. Not really sure what might have been wrong. Maybe someone can chime in and has an idea?

 

[benchwarmer]

I'm glad you got that fixed! Might want to read this before you think you have warped rotors. http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

 

[kelner]

thanks for the article. I have never broken in my brake pads (I've actually never heard of it, but it all makes really good sense) or rotors. Is it too late to do that now? Can I somehow roughen the surfaces of both pad and brake to start anew or would this require new components?

This is all assuming (like the article says) that the hub assembly and mounting interface is even.

 

[benchwarmer]

I have no idea. Hopefully someone who knows more will chime in.