Brakes won't bleed! Bad Master Cylinder? - Acura TSX Forum
 
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post #1 of 8 (permalink) Old 01-07-2017, 11:18 PM Thread Starter
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Brakes won't bleed! Bad Master Cylinder?

I have an '04 6MT that I did some brake work on and I can't get the air out of the brake lines. I replaced the front rotors and pads, and installed SS brake lines at all 4 corners. Master cylinder is full of fluid and there are no brake fluid leaks.

I did not know that Honda only wants you to go 1/2 way down with the brake pedal when bleeding the brakes, and so my wife/assistant pumped using the full travel of the pedal while I worked the bleeder valves. We made 2 rounds of bleeding each wheel, in the proper order and the pedal never got any firmer. There was no air coming out of the bleeder when I moved on to the next wheel, but when there was no pedal feel improvement after bleeding each brake, I returned back to each wheel and there was air in every line.

I replaced the 2 front bleeder valves, with no change.

The Acura manual says you can damage the master cylinder by going all the way to the floor, and since we were pumping for about an hour, I think it's trash. I didn't like the feel of the brake pedal in the first place, which is why I replaced the parts that I did originally.

Before I replace it tomorrow, is my master cylinder trash?

Any suggestions on trying to get the air out of these lines?

Why did Honda/Acura design a master cylinder that isn't supposed to go all the way to the floor? It doesn't make any sense when it seems as though every other car on the planet uses the full travel of the brake pedal!

Thanks for your help!
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post #2 of 8 (permalink) Old 01-09-2017, 11:46 AM
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Just checking, because I ran into this dumb mistake, but do you have the calipers on the correct side? Last week I ran into the same snag and then BAM I realized I had my front calipers on the wrong side and the bleeders were facing down. Swapped them over and bam air came right out.

I too thought my MC was taking a dump. If you've got your calipers on correctly it's pry the next place I'd look.

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post #3 of 8 (permalink) Old 01-10-2017, 10:41 PM Thread Starter
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Thanks for the suggestion, but I removed the calipers one at a time, so it's not that.

I got the new master cylinder bench bled, with no help from the chicken shit bleeder hose kit that came with it, got it in, and bled all 4 corners. A lot of air came out of the lines, but there was minimal improvement, the pedal still goes to the floor without much effort.

I'm about to do some of the tests for the brake booster called for in the TSX shop manual.

Does the brake booster have a high failure rate? I wonder if I can get the master cylinder far enough out of the way without disconnecting the lines...

Last edited by gumbalaya; 01-10-2017 at 10:42 PM. Reason: none
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post #4 of 8 (permalink) Old 01-11-2017, 12:03 PM
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Quote:
Originally Posted by gumbalaya View Post
Thanks for the suggestion, but I removed the calipers one at a time, so it's not that.

I got the new master cylinder bench bled, with no help from the chicken shit bleeder hose kit that came with it, got it in, and bled all 4 corners. A lot of air came out of the lines, but there was minimal improvement, the pedal still goes to the floor without much effort.

I'm about to do some of the tests for the brake booster called for in the TSX shop manual.

Does the brake booster have a high failure rate? I wonder if I can get the master cylinder far enough out of the way without disconnecting the lines...
The booster likely isn't the problem. Alls the booster does is make it easier to push the pedal. If the pedal still hits the floor you've either still got air in the lines or a bad MC.

Try this:

Functional Test

1. With the engine off, press the brake pedal several times to deplete the vacuum reservoir, then firmly press-and-hold the brake pedal for 15 seconds. If the brake pedal sinks, either the MC is internally bypassing, or there is a leak in the brake system. (mc, lines, prop valve, calipers, wheel cylinders, etc)

2. With the brake pedal pressed, start the engine. If the pedal sinks slightly, the vacuum booster is okay. However, if the brake pedal height does not vary, the check valve or booster is faulty.

3. With the engine running, lightly press the brake pedal. If the pedal sinks more than 3/8" (10mm) in three minutes, the master cylinder is faulty. (If the A/C is on, a slight change in the height of the brake pedal is normal.)

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post #5 of 8 (permalink) Old 01-12-2017, 01:40 PM Thread Starter
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Thanks for the info! I'm pretty sure that I accidentally moved the MC piston without lines hooked up and got air into when I put it in the other night.

So I bench bled it again and reinstalled it last night, bled the brakes, and everything felt great!

Right up until I started the engine and the brake pedal went to with 1" of the floor before it got firm. Pumped the brakes, with no improvement. I shut off engine, pumped the brakes and pushed hard on it for 15-20 seconds, with no pedal sinking or anything like that.

Started engine again, held brake pedal, shut it down, and the pedal seemed like it was rising ever so slightly, my leg didn't rise by it felt like my foot was moving up.

I ran through the booster check valve test, good vacuum, I pinched the vacuum line, pushed the pedal, went down near the floor, pumped the pedal several times, and the position did not change. Now I'm looking for a brake booster.

Should I go OEM or other for a brake booster? These guys seem like OEM, but not sure if they're selling knock-off OEM stuff. Anyone have any recommendations?

BRAKE MASTER CYLINDER - MASTER POWER for 2004 Acura TSX SEDAN
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post #6 of 8 (permalink) Old 01-12-2017, 04:53 PM
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I've never had an issue bleeding with the pedal all the way to the floor. I do it myself with no special tools. I'd be triple sure before buying a booster. This is not likely the issue anyway. I've had a booster fail on me...the pedal gets rock hard, that's all.

How to bleed your brakes the HTSpec way...by yourself...with no shouting.

Also you can always trust Heeltoe: Get Genuine OEM parts at oem.heeltoeauto.com

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post #7 of 8 (permalink) Old 01-13-2017, 04:08 PM
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What is the condition of your rear pads? I had a similar situation (not air on the lines though) with my ITR (pedal was spongy). I installed new pads and rotors in front and bled the system a couple of times with no success. Pedal remained spongy (and this is going all the way down with the brake pedal). Even replaced the MC and still the same (similar thinking as OP - did I mess up the MC?). Decided to replace the rear pads (they were worn maybe 1/2 to 2/3 gone) and this solved the issue. Firm pedal.

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post #8 of 8 (permalink) Old 01-26-2017, 11:47 PM Thread Starter
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Quote:
Originally Posted by MrHeeltoe View Post
I've never had an issue bleeding with the pedal all the way to the floor. I do it myself with no special tools. I'd be triple sure before buying a booster. This is not likely the issue anyway. I've had a booster fail on me...the pedal gets rock hard, that's all.

How to bleed your brakes the HTSpec way...by yourself...with no shouting.

Also you can always trust Heeltoe: Get Genuine OEM parts at oem.heeltoeauto.com
Update!

I figured I would try bleeding the brakes as described in the link by Mr HeelToe, so I figured, "what have I got to lose?" So I bled the brakes again, and there was no difference in pedal feel whether the car was running or not. So I said f*ck it, and shut it down for the night and would keep driving it as is, stomping on the brake pedal to come to a stop. The next day, I drove it out of the driveway, and about gave myself whiplash while coming to a stop from 4 mph!

I was a doubter of pumping the brakes with the bleeder valve open, but it worked in this case. Thanks for the tip!
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