first real (legal) drive with new master cylinder. the good & (moderately) bad - FFCars.com : Factory Five Racing Discussion Forum

NiceGuyEddie · 09-20-2012, 02:15 AM

i got my insurance card from Robbin today (e-mail so i could drive right away.)

i took the car out for 40 miles. i 'rode the brake' down big hills, stomped on it, everything i could think of. i even let the car roll backwards down and hill and hit the brakes.

my last master was a stepped one plumbed backwards. i put that right, and the braking is much improved. the feel of the pedal is much better. now that i have the "straight" adjustable brake rod from Breeze the brake pedal is more even with the clutch pedal (top height), and it does not "bounce" past the top. it also does not make a creaking noise, we learned that because the old pushrod was rubbing something.

the problem is that the brake pedal is still "sometimes faded." every 15 minutes or so, it will go 3/4 of the way down with nothing. not that i would really do that, if the pedal is "pre faded" as i call it, all i need to do is pump it again and it's ROCK solid from all the way up top.

most the time it's soft for 1" of travel or so and BAM they are rock solid. if i pump it twice, the second pump would be solid from all the way up top. the 1" of travel is identical to the free-play in my clutch pedal.

i bled the brakes all around more times than i could count, and i saw absolutely no bubbles coming out anywhere. all of the old fluid was pushed out, because all the new fluid going to the catch bottle eventually came out crystal clear. we went through two full bottles of brake fluid.

recently on TV... i don't remember which car show, but it's the one with the 'Larry the Cable Guy" sounding guy... they used a reverse bleeder. there are also youtube videos for it.

Harbor Freight has one for $27, Phoenix has one for $350.

advice?

Marc A · 09-20-2012, 02:18 PM

Did you bench bleed the M/C?
Marc A

FFR5452 · 09-20-2012, 02:31 PM

Hate to tell you this, Eddie, but you still have some air trapped somewhere. Probably in the m/c.

Silverstreak02 · 09-20-2012, 02:33 PM

When brake pads are initially changed the caliper pistons are pushed into the caliper as part of the process. The first time you hit the brake pedal it will travel all the way to the floor as it moves the piston out to contact the pads and rotor. It retracts slightly to release the brakes, but doesn't return completely into the caliper. The next time you hit the brakes the piston has to move only a short distance so the pedal travel is also short. I wonder if the self adjusting mechanism on one of your calipers has a problem. I believe you have an unusual caliper on the rear that has opposing pistons. I'd look at those first.

Jeff

pavieSD · 09-20-2012, 04:45 PM

Since you already have everything on the car, and I recall that you have the tools to make new brake lines, you can bleed the master cylinder on the car. You'll just need to build two new brake lines, plumb them back into the reservoir and pump the brakes until no more bubbles form. Here is a picture from an old Toyota:

NiceGuyEddie · 09-20-2012, 05:32 PM

yes, i bench-bled the master cylinder.

i thought about what Jeff said. since the problem is exactly the same as before, maybe there is something wrong with one of my calipers.

i have Wilwood rear and stock mustang front.

.

Hunter 2 · 09-20-2012, 05:39 PM

Reverse bleeding is the only way to go in 2012. You'll do it once and be done. The old fashioned way goes against the laws of physics as air likes to go up. So pushing the air up rather than attempting to push it down makes the job easy. Think about how difficult it is to try to push a ballon filled with air down in a pool. Very frustrating. I used the Phoenix. The HF one is...let's just say...you'll wish you had saved that $27 for lunch. I'd also suggest a NEW good old fashioned Jeep MC like you had before. Those Dorman MCs are harder to bleed. I have two of them.

QSL · 09-20-2012, 06:17 PM

Hunter, would that tool work in place of bench bleeding? How satisfied are you with the tool?

Someday I Suppose · 09-20-2012, 07:55 PM

What year Mustang fronts do you have? Any chance they are PBR's and swapped left for right? I seem to remember an issue where you could swap them and get an air bubble in the caliper.

-Scott

Quote:

Originally Posted by NiceGuyEddie

yes, i bench-bled the master cylinder.

i thought about what Jeff said. since the problem is exactly the same as before, maybe there is something wrong with one of my calipers.

i have Wilwood rear and stock mustang front.

.

Lex · 09-21-2012, 09:43 AM

Quote:

Originally Posted by Someday I Suppose

What year Mustang fronts do you have? Any chance they are PBR's and swapped left for right? I seem to remember an issue where you could swap them and get an air bubble in the caliper.

-Scott

I the calipers are reversed the bleeder will be at the lowest portion of the caliper hence not letting the air out as it would rise to the top section.

CraigS · 09-21-2012, 01:11 PM

In my experience air trapped in the lines doesn't just show up once every 15 minutes. The mushy pedal would be pretty constant. I wonder about axle endplay pushing the pistons back in the solidly mounted Wilwoods. That might be something that would show up intermittently depending on how much and how hard the car has been cornering prior to a given brake application..

PSB · 09-21-2012, 01:27 PM

Get yourself one of these: Phoenix Systems reverse bleeder http://www.summitracing.com/parts/PSL-2004/

I just replaced my master cylinder with a Wilwood dual setup. I "bench" bled the master cylinders in the car and bled the whole system in about 15 minutes. I'll never go back to the old way of bleeding brakes.

Pete

tirod · 09-21-2012, 01:32 PM

Agreed - air doesn't just come and go. Factory calipers are mounted on pins or guideways machined into the mount, and float to stay centered on the rotor.

BUT - Wilwood and other competition calipers are rigid, and the complementary rotor is mounted on pins to float. It uses a special hub to do that.

Something has to float, your choice.

NiceGuyEddie · 09-21-2012, 02:51 PM

hmmmm. more complicated than i thought, now axle play may be a problem.

out of fear of complications, brakes on DD's are pretty much the only thing i pay Pep Boys to do, but when the brakes go on my Tacoma in about a year, i plan to try it myself.

so a quality bleeder tool will be worth the investment.

another 150 mile drive last night, same results. just once the brakes were faded (3/4 way down and no pressure) - then the second quick pump and they were rock solid. i didn't even need to let the brake pedal get back to the top, just a wee up and BAM they are rock solid.

there is also a mysterious "leak", it's getting moist around the lip on the plastic reservoir. we are talking 2ml spread over the front part of the lip. the fittings are bone dry, and it does not seem to be leaking out the cap. at first, it was a wee over-fill, but i took some fluid out.

.

QSL · 09-21-2012, 03:36 PM

eddie, i just purchased one of those bleeders the other day after reading this thread. Should be here next week. Your welcome to try before you buy if you want.

Silverstreak02 · 09-21-2012, 04:05 PM

I still believe you have a piston in one of your calipers that is being pushed back into the housing. I believe you just converted from rear drum to rear disc brakes. I suspect the problem is in the rear if this just started since the conversion. Look over the installation closely.

Jeff

NiceGuyEddie · 09-21-2012, 10:51 PM

QSL: i planned to spend even a few more bucks on a higher quality unit that came with a case. we'll see how yours works out.

i will have to read about how to investigate my rear brake calipers locking.

could this in any way be related to parking brake tension?

Big Blocker · 09-23-2012, 01:31 AM

Eddie,

With your 5 link rear end, is there a chance that you pulled the axles out during your brake conversion?

Any chance you left out a "C" clip holding the axle in?

Once all bolted up (without a C-clip) the fact that the disk is captive by the caliper, you would have excessive free play pushing your caliper pistons back, causing a first press of the brake pedal condition not too far off of what you are describing here.

The axle would be floating back and forth as far as the caliper would allow it to, making it necessary for you to press the pedal twice to refill the piston reservoirs in the rear calipers, before there was disk pad movement sufficient enough to apply braking force.

Just a thought . . .

HTH

Doc

canuck1 · 09-23-2012, 05:18 PM

Sounds like pad knock back, where fixed (not sliding) rear calipers aren't able to reset pad position relative to the caliper piston and rotor. If your rear rotors aren't perfectly flat or (more likely) you have some axle end play, it can create a small gap between pads and rotor face as the pads get knocked back towards the (fixed) caliper piston causing a noticeable irregularity in brake response.

Not an expert, so I'm not saying this is what it is, only that it sounds like pad knock back.

I think Sanford has similar rear brakes and he has used 'helper springs' to minimize it. Might try contacting him.

Sean

Sent from my Autoguide iPhone app

NiceGuyEddie · 10-10-2012, 09:47 PM

i ordered the Phoenix reverse bleeder, and i seriously hope my problem isn't related to the rear axle...

will advise.

cheers,

NiceGuyEddie · 10-13-2012, 05:40 AM

UPDATE

here is Kenny with his new blue roadster. he gratuitously showed up to help me "reverse bleed my brakes in 10 minutes by myself."

the Phoenix tool is a good tool for the money, i'd recommend it to anybody. it must be nice to use when filling a totally dry brake system. brake bleeding is a messy job and i hate brake fluid, but it kept it to a minimum. when doing the rears, it was often times very hard to squeeze the trigger, and it would only squeeze halfway a few times. not sure why. i had to unsqueeze it by hand to get the plunger to get back to the first position. anyway, that's the tool.

there were a few times that i considered using it in reverse and sucking the whole system dry, but i did the rears twice, and kenny said he could see no bubbles coming out, nothing but fluid, and we had to drain the master several times. there is the little float in the master, it would be nice if that came out, but i could not get it out.

FFR5452 suggested there was air in the master cylinder, possibly there because i did not prime it well. the good news is that with the first pump of the passenger front, ken said he saw a bubble. it came up right away so i assume it was in the master cylinder. that was the only bubble we saw. by the way, it was much easier to pull the trigger on the tool with the front brakes.

went for a drive and the pedal feels the same. still 1 1/2" of free play but rock hard after that and the car stops very well. but after doing this i thought it would be hard all the way up top.

i did not get any pedal fade. i stopped the car 50x hard, and no problems. but the pre-faded pedal usually came after cruising for 10 minutes or more.

i drove Ken's car, his brakes worked absolutely awfully and i thought i was going to die.... i'm sure it can be improved, but his pedal was rock solid from up top and it seems like the pedal doesn't even go down 1/8" when pressing it. he has the Wilwood pedal box and dual master cylinders. (i don't expect my car to feel like his and i don't want to over-complicate my post.)

i am not sure if i solved my problem. that bubble definitely had to be purged out so it was already worth it. a longer drive is due to see if the pre-faded pedal thing went away.

the question is: we discussed the master cylinder - are there two chambers, front and rear? i think someone said there were two chambers, and it would make sense that with the first pump on the front the bubble would come out if there was a bubble in the front section of the master.

cheers,