Getting constant stream of air bubbles during brake bleed
Hello Everyone,
I am getting a lot of grief attempting to bleed the brakes of my 5th gen. (brake system is completely stock).
I recently purchased a Motive positive pressure bleeder to flush all the old brake fluid. It works by using air pressure (I used 15 psi) to push brake fluid into the reservior on top of the master brake cylinder..
I followed the proper bleed order (according to the shop manual) for a 5th gen: driver-front, passenger front, passenger rear, and then driver rear. I made sure that the reservoir was always filled with fluid, well above the min line.
The brakes felt really mushy after the flush. The car seems to stop well enough on a dry surface during a short test drive, but still, I can push the brake pedal all the way to the bottom if I apply reasonably firm pressure.
So I repeated the same brake flush proceedure a second time:
I am getting a constant flow a small air bubbles from the two rear calipers only. This does not happen with the front calipers. The fluid was intitially clear for the first 30 seconds then the bubbles started to appear. I have gone through 2 liters of brake fluid with no end to those bubbles. I am just sitting there, looking dumpfounded at the clear pipe and wondering where the hell are all those bubbles coming from.
When the engine is on, the brake pedal is still very mushy. I am going to try holding the jar and bleeder pipe above the level of the bleeder screw to make sure air isn't being drawn in around the screw due to the "siphoning" suction as fluid flows down a pipe. The brake pedal is still very mushy.
I read somewhere, on a non-honda forum, that stated that vacuum and positive pressure bleeder tools simply do not have enough oompf to kick out all the trapped air from a brake system and the only way to get them out is to use the traditional 2 man approach.
If my next attemp also fails, I guess I will try the traditional 2 man approach.
Do a manual bleed by pumping the brake pedal instead of using the vaccuum pump.
I did it first with the vaccuum pump with bad results - brake pedal would not feel stiff when pressed on. Afterwards, doing it via the manual way produced better results.
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Name: Jack-in-the-Box -|- Car: Meep-meep -|- 2001 EBP Type SH Gremlin Infested. Do Not Add Water. Seriously, DO NOT ADD WATER. RIP. To be replaced.
I do not need to explain anything to you.
My broken wings still strong enough to cross the ocean with.
My broken wings how far should I go drifting in the wind.
Yes, as soon as it stops raining here (and I could lure in an assistant with some free pizza), I will try bleeding the brakes manually.
It is very strange though. I can understand how a vacuum pump could get air into the brake system: Air can be drawn in from around the loose bleeder screws that Preludes have, but I am still puzzled how a positive pressure tool (which pumps fluid from the top) could caused air to get in. If anything, the latter method would cause fluid to leak out from any loose connections, not cause air to be sucked in. I would indeed be curious to know what I am missing here.
Really Ken? Mine is still stock and I am at 107xxx miles.
__________________
Name: Jack-in-the-Box -|- Car: Meep-meep -|- 2001 EBP Type SH Gremlin Infested. Do Not Add Water. Seriously, DO NOT ADD WATER. RIP. To be replaced.
I do not need to explain anything to you.
My broken wings still strong enough to cross the ocean with.
My broken wings how far should I go drifting in the wind.
OK, I got the problem fixed this afternoon. After doing some research I found out that air can leak in from around the bleeder screw, even when using a positive pressure system (e.g. Motive pump tank), due to suction created by the siphoning force as fluid flows down the bleeder hose.
This morning I used instead the traditional 2-person brake pedal approach. Also, I took the precaution of cleaning the bleeder screws and putting a little motor oil on the threads to prevent air leaking in. Two big air bubbles came out of the front-left caliper (bubbles always used to come out the rears on the two previous attempts ) and few small ones on the front right. No air came out the rears. Now the brakes feel as good as new.
The master cylinder is still in great shape according to the press-and-hold test and the fast-press slow-press test (as stated in the shop manual).
Really Ken? Mine is still stock and I am at 107xxx miles.
I mean there is some variation, but a lot of owners have to replace their MCs like clockwork around 100k miles. There are seals in there that will degrade over time. Kinda a function of usage on how fast.
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I am not an active moderator on this site anymore. Please contact Phryxis or liquidxnitez for help with your issues.
Mine was still good at 175k and Rays old car still has a good one and that car is around 150k+ now.
I think you might have had too much pressure, we just did this same thing over the weekend on Sees car wtih good results. I was using it at around 5-10psi.
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