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Car Forum / Honda Cars / August 2007Air in brake lines or hosed master cylinder?
The short story: I screwed up and depressed the brake pedal with the caliper off the car. The piston came out, along with a bunch of fluid. Got the piston back in and everything buttoned up, but now the pedal sinks to the floor. The long story: A simple pad change turned ugly when I decided to flush the fluid while I was in there. I got the piston back in place, with the rubber boot over the piston. I assumed I was good to go, but the pedal goes to the floor with the ignition on. From what I can gather this is one of the two problems in the subject line. The vehicle is a '97 Civic EX w/160k miles. I hadn't flushed the lines in about 70k. The fluid (SynPower) was discolored, but wasn't horrible looking. I went to the rear right tire and started bleeding there with a MityVac. The fluid spewed out of the SpeedBleeder, which I take to mean that there was a ton of air in the lines, from the piston coming out. I did this for a loooong time, and, although I got clear fluid, I never got anything more than fluid spewing out a little a time. I put everything back together and moved to the front left caliper (where the problems started). Here, I was able to get a better fluid/air ratio, but still bubbles coming out the bleeder. After I ran through my 2nd liter of GT LMA since starting this process yesterday, I quit. Questions: 1) Does it normally take that much time and fluid to clear the lines of all air? At $8/liter, this is not fun. 2) How can I tell whether the problem is MC or air? Or do I have to finish the full bleed to determine that? Any and all advice appreciated. Anyone in Cincy is welcome to stop by and take a rotation on the MityVac. :) -Patrick > The short story: > [quoted text clipped - 40 lines] > > -Patrick 1. pinch off the rubber caliper hose - using the correct tool to avoid damage to the hose. 2. open the bleed nipple. 3. force the piston all the way back into the housing allowing the fluid and any air out. 4. close bleed nipple and remove the pinch tool. 5. bleed the system with someone assisting you - have them press the pedal on your command - press, open bleed, close bleed, release pedal. repeat. self-bleeding kits don't always get rid of air locks - and that's what it sounds like you have. you may also want to consider bleeding at the master cylinder by loosening the connecting hoses. use an assistant as above. have a hose ready to wash [NOT WIPE] any fluid off paintwork. oh, and make sure they press the pedal to the floor. it's the only way you can ensure air removal with an airlocked m/c. > 1. pinch off the rubber caliper hose - using the correct tool to avoid > damage to the hose. What is the correct tool? > self-bleeding kits don't always get rid of air locks - and that's what > it sounds like you have. you may also want to consider bleeding at the > master cylinder by loosening the connecting hoses. Should this be done before or after bleeding at the wheels? Also, is it possible to force fluid up the lines from the wheels to dislodge an air lock? Thanks. >> 1. pinch off the rubber caliper hose - using the correct tool to avoid >> damage to the hose. > > What is the correct tool? this is one design. http://www.thetoolwarehouse.net/shop/LIS-22850.html there's another i prefer because there's less temptation to over-tighten, but that takes more searching. google this group - it's been discussed before. >> self-bleeding kits don't always get rid of air locks - and that's what >> it sounds like you have. you may also want to consider bleeding at >> the master cylinder by loosening the connecting hoses. > > Should this be done before or after bleeding at the wheels? do it first. you'll have to return to the calipers again after you're done with the master cylinder, but it's the best place to start with a problem like this. > Also, is it possible to force fluid up the lines from the wheels to > dislodge an air lock? no. you can force fluid up, but it won't dislodge an airlock. You have to make sure the piston seal is intact and sealing and the caliper isn't leaking air anywhere (eg hose connection). I personally would not clamp a reinforced brake hose. Depending on the internal construction you could permanently collapse the hose. I'd say one liter (quart) of brake fluid should be sufficient to fill the entire system. However, if you got air into the master cylinder, you probably have to bleed it using an inexpensive kit from an auto store (bench bleeding kit). Tegger has an excellent writeup on bench bleeding: http://www.tegger.com/hondafaq/mastercylinderreplace/benchbleeding.html Both Castrol GT LMA (Low Moisture Activity) and Valvoline SynPower are very good fluids. I'd avoid the Honda DOT-3 made by CCI. IMO good dry boiling point but otherwise overpriced junk. I and many others have pulled calipers. No problems afterward. In the longer term I'd suggest a PowerBleeder from Motive Products. www.motiveproducts.com > Questions: > [quoted text clipped - 8 lines] > > -Patrick Similar subject: On an '00 Acura TL. After new installing rotors and pads when I'm braking the car pulls to the right. I noticed with the left caliper off, and pumping the brake, that it the piston came out very very slowly. It took two full travels of the brake pedal to get it to come out about 1/3". I had a clamp handy so as to not have the same issue as Patrick. Does this indicate a hanging caliper? Or perhaps a restriction in the brake line? > Similar subject: On an '00 Acura TL. After new installing rotors and > pads when I'm braking the car pulls to the right. I noticed with the [quoted text clipped - 3 lines] > same issue as Patrick. Does this indicate a hanging caliper? Or > perhaps a restriction in the brake line? how are you going to get a restriction in the brake line? is the hose kinked when you're trying to pump the pedal? otherwise, the pump ratio is correct - the master is small, the caliper has large pistons in comparison. the caliper piston is seized if the caliper piston offers resistance to the brake pedal when pumped. simply disassemble, with regard to the componentry you'll see in the workshop manual, clean, silicone grease, then reassemble. There were reports of rear pads wearing a lot faster than fronts on Hondas. Maybe it's the caliper seizing? > how are you going to get a restriction in the brake line? is the hose > kinked when you're trying to pump the pedal? otherwise, the pump ratio [quoted text clipped - 3 lines] > regard to the componentry you'll see in the workshop manual, clean, > silicone grease, then reassemble. So if you were to use the piston retraction tool to push it back, do you notice significantly more resistance on the left caliper? Time to put in a rebuilt caliper? If there is corrosion, you probably don't want to attempt a rebuild yourself. Besides, you need a special tool to depress the spring while removing the snap ring for the E-brake rear caliper AFAIK. With each caliper change it's a good time to put in a new brake line too with new crush washers. > Similar subject: On an '00 Acura TL. After new installing rotors and > pads when I'm braking the car pulls to the right. I noticed with the [quoted text clipped - 3 lines] > same issue as Patrick. Does this indicate a hanging caliper? Or > perhaps a restriction in the brake line? |
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