What's wrong with my brake system?

[LittleRed4wd]

So during the past week I've been doing lots of work to my wagon, including the vented rotor brake upgrade. When I pulled off the original calipers I forgot to cap the lines, so the master cylinder drained. I figured it was fine, since I was gonna replace all the fluid anyways. Fast forward to yesterday, when I finally got all my brake parts together. I put everything on (I highly recommend the 1/8th inch spacers from synthdesign, perfect fit), filled up the master cylinder, and noticed the brake pedal would go straight to the floor with no resistance. I figured no big deal, I just gotta bleed the calipers. So I did that and still the pedal goes straight to the floor. I went back around and noticed the rear passenger cylinder still had lots of air bubbles coming out, and I spent about an hour straight bleeding it with no signs of the bubbles decreasing. Is there something wrong with the system or is there just a ton of air in there? I didn't touch any part of the rear brakes, except for letting the MC drain. Nothing was leaking prior to pulling the front setup apart.

Unless I can think of another possible problem I think I'm going to pick up a vacuum pump/bleeder thing tomorrow and try that. (I've been doing the one person on the pedal and one on the bleeder deal). Any suggestions?

[Jarf]

It is never a good idea to let them run dry. How long was it empty? long enough for the seals to dry out? Not too mention that all the crude in the bottom of the master drained out past those seals in the master.
While it is possible that damage has occurred it is just as possible that you have other problems.
First make sure you have no leaks, it is possible to have a leak small enough to allow air to enter but not fluid to leak out.
Just because you didn't open the rears doesn't mean you haven't introduced air into the rears.

Top up the master, pump the pedal until you get a bit of pedal, while your assistant holds pressure on the pedal and start with the RF, then the LF.
Refill the master religiously.
Pump up the pedal, now include the rear (RR,LR,RF,LF).
Do this several times, the pedal should slowly improve, if it does not, you either have a leak or a trashed master (not so likely but not unheard of).
PAY close attention to the flex line connections.
If things don't improve, check the metal lines to the flex lines and verify there are not cracks, deformed flares or dirt in the threads.

Also a good idea to work out a plan with your assistant before hand.
For me, I use "pump", assistant pumps until he gets a pedal at which he announces "holding" (and stops pumping). You crack a bleeder, he tells you when he is down, you close the bleeder and reissue the pump order.
Keep the commands/dialoge to a minimum and there will be less chance of operator error.
While it sounds kinda stupid, I have more than my fair share of assistant induced problems, which created the above routine.
Nothing worse than having a noob doing the pumping and not being aware that he MUST keep the pedal down until YOU order pumping to resume (all bleeders closed)

[LittleRed4wd]

Thanks Jarf- I'll try that. The MC sat empty for about 4 days- oops! It may be time for the mr2 upgrade...

[SynthDesign]

Air bubbles are a pain! In instances like that, yeah it's happened to me a few times, I normally bleed the system, let it sit for a few hours and bleed it again. Sometimes it takes quite a bit of time to work out three or four small bubbles stuck in the master cylinder. Tapping the lines and cylinders/calipers with a rubber mallet helps to free them too.

Best of luck!

[dlb]

ditto on synth. i had to replace a few brake hoses recently and was surprised at how long it took to get all the air out of the line. just keep it up.

[Petros]

I do not think it is possible to bleed the brakes without an assistant pumping on the brake pedal. IT takes lots and lots of pumping to get all of the air and old fluid out if it was opened up. Power bleeder might help, but it is not substitute for doing a proper, sequential bleed of the system, start and the rear brakes and work forward.

DO NOT let the master run out of fluid at any time. Or you will have to start over again since you will pump air into the system again.

Good luck

[larry mcgrath]

I just finished the brake up grade, with a master cyl that was EMPTY for who knows how long.what you MUST DO before you hook up the 2 brake lines to the master cyl is to blead the air out of the master cyl. To do this take 2 old brake lines and connect them to the master cyl and bend them so they go over the brake fluid resivor and into and below the fluid level,pump the brake pedal repeadly,make sure the ends of the brake lines stay smurged in fluid.by pumping the peadle you will fill the pistons inthe master cylinder. Other wise it will take forever to fill the master cyl because of an air lock in the cyl ,hook up the 2 brake lines and blead the brakes THis is the best way to solve this problem works every time.

[GLet71]

Hey, that's a great little tip you got there Larry!

[LittleRed4wd]

Well I figured it out- the wheel cylinder was leaking so that only air would get in, but no fluid would come out. Fixed that and of course one of my front calipers siezes up. Looks like the brakes are going to take a bit longer...

[Lil Beast]

Was about to mention make sure all the brass fitting to be tight, or bench bleed the MC! Sounded similar to my fuel system problem had gas bubbling, cause of a crack in the brass!

[deejay1272]

I am having a similar problem. After bleeding the rear driver side brake line I could not get fluid to come out of the bleeder nozzle at all (even with an assistant pumping the brakes). This also happened at the front passenger side but i was able to see some very small qmount of flow at the bleeder.

No matter how many times the brakes were pumped, no fluid would come out of the rear driver side brake bleeder. This was NOT the case on the rear PS or front DS where fluid flowed freely between cracks on the bleeder nozzle.

I didn't bleed the (new) MC because I figured I had to bleed everything anyway since I was also replacing the brake hoses as well as the MC.

Do I need to bench bleed my MC anyway? Why am I getting no flow at my rear DS and only low flow at front PS bleeders?

[ARCHINSTL]

You should bleed the new MC - every one I've ever installed, even waaay back when had this in the instructions. It's less awkward to do this before installing (whence the term "bench bleeding"), but it can be done. Most (all?) new MCs come with little bleeder kits.
As to the reason for little to no flow from several points - I'd guess that the previously mentioned crud has made its way through the piping. Either that and/or some rust in the wheel cylinders is clogging the bleeders. I'd suggest removing the bleeders and blowing through them.

If this still does not work, then what I would do is to blow compressed air through the disconnected lines - put a hose on the lines and run it into a bucket with some kind of cloth in the bottom to catch and view any debris that is ejected.
Note - that is what I would do - cannot vouch for its efficacy.

I had the prob with no flow through, oddly, the same two bleeders you mentioned the last time I bled Goldie's - turned out the two bleeders were clogged.
Tom M.

[dlb]

+1 on tom's response about plugged bleeders and lines. i would try the easiest thing first: remove the offending bleeders; plug the hole with a rag or rubber cap as best you can; use compressed air to blow the bleeders out; put them back in and try bleeding the lines again. if that doesn't work, than i would try the more tedious task of disconnecting the lines at both ends and blowing them out with compressed air. i recently blew out the fuel lines on a project tercel and didn't come up with a good way to secure rags to the ends of the lines. wound up blowing crap all over the walls of my car tent. hopefully you're more creative than i am if you have to do that.

[Jarf]

my money is on plugged bleeder screws. Just remove the dang thing and clean it out from both ends with a 1/8in drill bit, they get FULL of crude.
I prefer to operate the drill but by hand but in extreme cases power-drills work too, just be very careful, or just get new bleeder screws and call it done.

If that is indeed your problem, after you get it all cleaned out (do ALL the bleeders if you find this to be the problem) then when your done, drop by your friendly dealer and collect a bag of bleeder screw condoms (my word, not Toyota's) they come in packs of 10 and are pretty cheap, especially compared to spending a couple of hours cleaning up
rusty bleeders, or better yet, replacing wheel cylinders and calipers because the bleed screw has broken off.
If you take the bleeder out and fluid starts draining, you know your problem is the bleeder screw, itself.

Blowing with compressed air , while effective, has it's dangers, brake fluid is nasty stuff whether it gets on your paint or in your eyes, be very careful.
(remember that if you blow 150psi into a line that is dead-ended, it will come back at you with the same force but with airborne liquid)

Don't blow out lines that are attached to components, if you must blow the rear line with the wheel cylinder attached to the line, have the shoes and drum installed, to stop the cylinder from exploding.

[deejay1272]

I will check on the plugged bleeder screws soon. That one makes sense to me. I just hope I don't need to have a vacuum bleeder machine to fix this!

Since my lines are so full of air already, I might as well replace the rear brake hoses as well and then start all over with the bleeding process. Can't wait.