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Old 02-05-2009, 11:33 PM   #1
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Default Brake help!!!

Ok, this is a question about the crx im rebuilding. I replaced the MC, prop valve, and all 4 calipers. I bench bled the MC before installing. All 4 corners have been bled in the correct order and no bubbles are coming out anymore. The pedal is firm and the brakes have enough holding power that I was able to tq the axles nuts to about 150ftlbs with 0 slipping.

Heres the squeeze though, after pushing on the pedal on the upstroke a stream of air bubbles can clearly be seen coming up from what appears to be inside the master cylinder up into the reservoir. It doesn't seem to affect pedal pressure, but I'm sure you can appreciate my unwillingness to drive it since it seems very abnormal.

There is no fluid leaking out anywhere, so I don't have a clue where air might be entering the system, yet it is somewhere. Any constructive ideas what might be causing it?

BTW, the brake system is nearly identical to the miata's.
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Old 02-05-2009, 11:45 PM   #2
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Ok, this is a question about the crx im rebuilding. I replaced the MC, prop valve, and all 4 calipers. I bench bled the MC before installing. All 4 corners have been bled in the correct order and no bubbles are coming out anymore. The pedal is firm and the brakes have enough holding power that I was able to tq the axles nuts to about 150ftlbs with 0 slipping.

Heres the squeeze though, after pushing on the pedal on the upstroke a stream of air bubbles can clearly be seen coming up from what appears to be inside the master cylinder up into the reservoir. It doesn't seem to affect pedal pressure, but I'm sure you can appreciate my unwillingness to drive it since it seems very abnormal.

There is no fluid leaking out anywhere, so I don't have a clue where air might be entering the system, yet it is somewhere. Any constructive ideas what might be causing it?

BTW, the brake system is nearly identical to the miata's.
Sounds like a bit of air is still in the system and has worked it's way up to the master cylinder. When you push the pedal, the fluid moves down a bit and the air goes down with it, but then rises back up. You let off the pedal and fluid flows up into the MC and a bit of air also came with it. How did you bleed the system? Manually or with a hand held vacuum pump? The hand held vac. pumps make this so easy and fast, it's stupid. Also if you didn't rebuild the MC yourself if never hurts to tear it apart and make sure it was done correctly. I've seen new ones that had a bad seal out of the box.
CRX FTW. Friend has a 89' si. I almost bought it off of him. Best honda period.
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Old 02-05-2009, 11:49 PM   #3
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Ive tried both manual and mitivac. The lines are so clear of air is stupid! I pumped the pedal for like 5 min and ****** bubbles still come up out of it. These are big *** bubbles, not just little tiny ones. Its whack!

Ya the crx is an 89 HF. I rebuilt the stock motor over christmas. The brakes are the final piece for me to get it on the road for DD duty.
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Old 02-05-2009, 11:56 PM   #4
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Weird. You think it's air coming out of the system of there is air getting in somewhere? If you stand on the pedal with vacuum to the booster does it stay hard? I can't imagine it getting air in the system after the master and it not leaking fluid under pressure. I'm gonna say bench bleed the master again. They're a bitch sometimes. I always bench bleed it till I know there isn't any air in it, then do it that much more. I always get a spec more out eventually. Try tapping on it with the end of screwdriver to get any tiny air bubbles stuck to the walls of the cylinder and whatnot to let go and flow out. Picture taping on a cup of soda and the bubbles stuck to the sides float up. Same thing for the calipers, etc.
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Old 02-05-2009, 11:58 PM   #5
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Ah, you said new calipers. I missed that. They most certainly still have air in them. It's a bitch getting them full of fluid when new.
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Old 02-06-2009, 01:59 PM   #6
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If it had that much air in the system, he would not get a hard pedal. However, if air were being drawn into the system, you would expect that the fluid would leak out, especially under pressure. Are there any loops in the brake lines around the proportioning valve, or anywhere else in the system that could hold air bubbles?
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Old 02-06-2009, 03:02 PM   #7
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no loops in the system, no leaking fluid, firm pedal, lots of bubbles on upstroke....
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Old 02-07-2009, 03:05 PM   #8
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I HATE YOU PAT!!!!

I got a chance to work on it this morning, and went ahead and bench bled the master again. Well....after doing that and bleeding the system again there are no more bubbles. Brakes are good to go!
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Old 02-07-2009, 03:20 PM   #9
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yay!
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Old 02-07-2009, 03:24 PM   #10
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I HATE YOU PAT!!!!

I got a chance to work on it this morning, and went ahead and bench bled the master again. Well....after doing that and bleeding the system again there are no more bubbles. Brakes are good to go!


"Told ya so..." Whenever I change a caliper I always end up bleeding the system twice if I care about pedal feel.
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