Got Air in Lines Bleeding Brakes

So, I screwed up the job bleeding my brakes on the Miata. I got to the very last corner, the left-front, and didn't keep a close enough eye on the reservoir, and sucked air into the brake lines.

Do I need to totally re-bleed the whole system? Or can I just keep bleeding at that corner until there aren't any more air bubbles? Or maybe bleed just the front two lines but leave the back?

When I had my friend keep pumping at that corner, it seemed like there continued to be a couple of small bubbles. I called it a night because we were tired and I wanted to check with this board.

You might get lucky with a reverse bleed of the system. Use a mighty vac in reverse with the special cup they provide.

Otherwise build yourself a pressure bleeder and never worry about running out of fluid.

Seriously, a quick Google and I find:

http://faculty.ccp.edu/faculty/dreed/campingart/jettatech/bleeder/index.htm

This needs to be a tech-tip and EVERYONE should go and build one now if they don't have one.

fiat22turbo wrote: Otherwise build yourself a pressure bleeder and never worry about running out of fluid. Seriously, a quick Google and I find: http://faculty.ccp.edu/faculty/dreed/campingart/jettatech/bleeder/index.htm

For a home pressure bleeder like that, I got an interesting tip for making a universal one. The suggestion was to use a schrader (sp?) valve, like what's used for grease guns. Then you can install a nipple on the master cylinder cap of any car you own, and have universal pressure bleeder.

But I don't think I'm going to do that in the next day or two, and don't have a mighty-vac.

Also, I heard that the old-fashioned way actually yields better results if you have the time to do it.

I don't think so. I've done the old fashioned way for years and I've used my DIY pressure bleeder and the results have been the same.

Why? Either way, you have to slow down and pay attention. With the pressure bleeder you just have to pay attention for a shorter period of time.

For quick bleeds, the old fashioned way is still fine, especially at say a track day, etc.

I built my bleeder in an afternoon, so I'm not sure why you'd discount building one quickly.

I don't have a dremel tool or air compressor as the instructions suggest. Do you have a suggestion for a substitute? I will have to go to my parents or grandparents to borrow a drill.

But the question still remains: should I re-bleed the whole system? Or just the one line that got air introduced to it?

Salanis wrote: I don't have a dremel tool or air compressor as the instructions suggest. Do you have a suggestion for a substitute? I will have to go to my parents or grandparents to borrow a drill. But the question still remains: should I re-bleed the whole system? Or just the one line that got air introduced to it?

Look through the instructions, you don't need an air compressor for any of it, its just to fill the tank if your too lazy to pump.

Instead of a dremil you can use a drill, a razor blade, a rusty nail, a bic lighter anything that can puncture plastic.... Your just making a hole, dremil was just his suggestion, the author mentions not even measuring and the whole thing seals with an o-ring, just get it close.

as to whether or not you need to bleed the whole system, what is the car used for? If your gonna go race it I would want to make damn sure there is no air anywhere, and you might as well go back around and bleed it... Its not fun, but come on how hard is bleeding brakes really?

If its just a commuter try and bleed that side until the bubbles absolutely stop and then try it cautiously... If it stops its stop.

Eh, it's my track car and I'm hitting the track again in a week. I figured I'd probably have to do the bleeding job all over again, I was just hoping I was mistaken. Oh well.

At least if I build this tool, I won't need to rely on someone else's schedule to take care of the job.

Rebleed both front lines.

I didn't use a dremel, just a drill and a drill bit, a hand saw and a sharp knife. It is just bloody plastic after all.

I've got/had/used pressure bleeders, vacuum bleeders, check valves, and probably several other things for bleeding the brakes.

Always come back to the best. A 2' length of clear tubing and a can. A little fluid in the can, slip the tube over the bleeder and into the can, crack the fitting. It works better than any other method or tool I've ever used.

foxtrapper wrote: Always come back to the best. A 2' length of clear tubing and a can. A little fluid in the can, slip the tube over the bleeder and into the can, crack the fitting. It works better than any other method or tool I've ever used.

That's pretty much what I have been doing. Don't I still need to have someone pump the brakes though?

Nope, that's why there's the fluid in the container, to prevent air from being sucked back into the system on the return pedal stroke. After the fluid starts to flow out of the bleeder and into the tube it'll prevent that problem pretty well anyway. I use a "one man" bleeder kit I got for cheap from Sears years ago, it's a 90* rubber fitting that goes onto the bleeder and attaches to a short clear line into a cup to hold the old fluid. Start with a little fresh fluid in the bottom of the cup and then pump (slowly) away. Works like a charm.

If you've got a long enough clear tube, you don't need a helper, or even fluid in the bottle....you can usually just get out of the car and close off the bleeder screw before the bubbles make it back to the caliper.

Once the MC has been aerated, you'll want to bleed, then bleed again...and then drive some...and bleed again. There will be bubbles trapped in there for a few bleeds. Keep rebleeding until the pedal/brakes are firm.

Per Schroeder wrote: you can usually just get out of the car and close off the bleeder screw before the bubbles make it back to the caliper.

I put a loop in the clear tube. This way the bubbles get trapped at the top of the loop if they are in the tube when I stop pumping the brakes. Otherwise bubbles will get forced by the loop and exit the tube.

Another thing I have noted is that smaller ID tubing is better. You get a tighter fit to the bleader and a more rapid expulsion of the fluid through the tube (think hydraulics / volume here). As well as the tube will usually be cleared with a single pump of the brakes.

Per Schroeder wrote: Once the MC has been aerated, you'll want to bleed, then bleed again...and then drive some...and bleed again. There will be bubbles trapped in there for a few bleeds. Keep rebleeding until the pedal/brakes are firm.

Hmm... that's even worse than I was worrying. So, basically, I'm going to want to completely re-bleed the system twice now? Grr... I was so close to being done before this happened.

It just depends on how much air got pumped in there. When I've gotten air in the MC, I start with the shortest line (usually LF) and pump all the air out through that one. Then I go on to the longer lines. No biggie.

Per Schroeder wrote: It just depends on how much air got pumped in there. When I've gotten air in the MC, I start with the shortest line (usually LF) and pump all the air out through that one. Then I go on to the longer lines. No biggie.

I didn't get too much in. I was watching the line while my friend pumped, and the MC had just started to suck in air with the brake fluid. I topped the reservoir as soon as that happened.

So... it sounds like my best course of action is to bleed the lines in reverse order? If I do this myself, just pump everything out through short line (which is the one that got the air, until there are no more little bubbles in the line, then work my way backwards through the other lines, checking to be sure I stop getting air bubbles in them?

Yep. that sounds reasonable. Which line were you bleeding when the air got in? that might be the one to start with, followed by the shortest....

Per Schroeder wrote: Yep. that sounds reasonable. Which line were you bleeding when the air got in? that might be the one to start with, followed by the shortest....

I was on the shortest line when I got air in the system.

I'd gotten pretty much everything out of the system and was having my friend give it a few more pumps for good measure. Just as I was about to tighten the valve, I saw a bubble.

You can also get those "speed bleeders" which are just replacement bleeders screws for the cylinders with a one-way valve in them (available at PepBoys type stores under the FixIt section). A brake fluid filled cup will basically do the same thing, but you have to be a bit more careful to make sure the seal is good.

A note with the Schrader valve on the master cylinder: This could turn into a huge mess!! Since the Schrader valve is a one-way valve, when you finish bleeding there will still be full pressure in the reservoir. Guess what happens when you take the cap off to lower the fluid level down the the full mark!!

This is the biggest pain of the power bleeders, the potential for a big brake fluid spill when you take the cap off. This a much bigger issue with the older style master cylinders.

Yeah, I used the auto parts store hose with one way valve and it works like a charm.

Salanis wrote: Eh, it's my track car and I'm hitting the track again in a week. I figured I'd probably have to do the bleeding job all over again, I was just hoping I was mistaken. Oh well.

I was with taking a short cut until I saw this was a track car. Do it right. Don't scrimp on brake maintenance for a track car.

That said...

I usually bleed by putting a long hose on the bleeder. I take that line and use a tall cup or bottle with about an inch of brake fluid in the cup/bottle. I then put the hose in the bottle. After that's done I crack the bleeder. The hose, at this point, is attached to the bleeder and flows away into the cup/bottle with the bottle end of the hose submerged in the brake fluid. Then I start pumping the brake. I pump it a lot as I usually can't see the whether there are bubbles or not. A friend would help here but I'm a loner, a rebel. There are things you can't know about me..thinks you shouldn't know...anyways...

Once I'm done pumping I close the bleeder valve. After the bleeder is closed I pull the hose and go to the next one. Don't let the reservoir go empty using this method. Then you'll be where you are now.

I do this on all four corners. I get a pretty good bleed with this by myself most times.

I'm reading about the other bleeder now.

I have to tools to take care of this myself then, and can start on it after grabbing some more brake fluid. Unless people think I should wait until I can grab an assistant who will be able to tell me when there are no longer bubbles in the lines.

Salanis wrote: I have to tools to take care of this myself then, and can start on it after grabbing some more brake fluid. Unless people think I should wait until I can grab an assistant who will be able to tell me when there are no longer bubbles in the lines.

An ass-istant will help you to do it right the first time. I usually rely on physical effort to overcome the lack of team work. In that case I pump the pedal a LOT. I have refilled the brake reservoir two or three times on some jobs. Why not? They say use an unopened brake fluid container each time. So why not use the WHOLE container on one job right?

Snagged a friend into helping with the job. As luck would have it, he was actually knowledgeable on what's involved with bleeding brakes.

One of the best parts of it is, he's too big to fit in my Miata, so I got to man the pedal while he messed with the lines!

I think we got all the air out. Pedal feels about like it did before the job (fluid wasn't too bad, just wanted it as fresh as possible for the track next week). I'm going to see how the pedal fairs when I bed the new pads in.