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Installed new Master Cylinder and pedal goes to the floor

 
uget2nd
I love my Chevy Chevette!
Posts: 10
Joined: 04/13
Posted: 07/06/13 05:55 PM

Friends,

I just installed a new Tuff Stuff long bore Master Cylinder. 1 inch piston. Dual port
The master cylinder that I replaced had the same specs.
I didn't bench bleed it but I cheated by installing it on the car and pumped until the bubbles were gone.
Hooked up the lines and bled each brake.
The problem now is that the pedal goes to the floor with some, but little resistance.
I bleed with two people. One to push the pedal down while the other person releases the bleeder and then lets the pedal up once the bleeder is tight
What am I over looking.
I bled the breaks about 10 sequences each., and went thru almost 2 bottles of fluid.
Can you help me out  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 07/06/13 07:32 PM

well...   what kind of braking system do you have????


disc on the front... disc on the rear..

disc on the front.. drum on the rear..

drum all the way around..


just curious...   long bore.. or DEEP bore/shallow bore...    the deep bore shallow bore is the depth of the hole in the back of the master cylinder piston..

if you have installed a deep bore master on a shallow bore booster.. the push rod will move about an inch.. before it contacts the back of the piston...


i have several ways of bleeding the brakes...

with 2 people... i start with the lines disconnected at the master...  holding fingers tight over the holes.. i have the person in the drivers seat start to pump... i usually get fluid out of one side first.. then the other side..  i am using my finger tips as check valves..   this is hard on painted engine compartments... i always wash down with water asap... as soon as i get fluid from both sides... i hook up the lines...  snug them..  put a wrench on both.. have the person in the drivers seat pump 3 times and hold.. i loosen both lines while the assistant pushes to the floor.. i tighten the lines..  have them let up the pedal and pump 3 more times and hold..

i can tell when i am loosening the lines right at the master if i am getting air from the master..  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 07/06/13 07:41 PM

so... can you describe your braking system...

if you have disc brakes... and the fluid all thru the system is truly clean and fresh.. not just at the master..

you can retract one of the front brake calipers and this will push fluid back thru the  system... this is not a great way to bleed the brakes...

its harder with rear disc.. as some rears have a parking brake built into the caliper..


you can also try this... when i am alone.. and need to bleed brakes..

i have a  bleeder screw partially open..   just a tiny amount...

i play whack a mole with the brake pedal.. but just barely bumping the pedal...  what i am doing is building pressure in the master... but not  moving the piston far enough to close off the fill port into the reservoir..

if the piston seal moves past the fill port.. when it moves back it will create suction and pull air in at the bleeder screw..

i only do one wheel at a time...

what happened to cause you to change the master..?????  was it going to the floor before the new was installed.???  

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uget2nd
I love my Chevy Chevette!
Posts: 10
Joined: 04/13
Posted: 07/07/13 04:35 AM

No booster. I have no room
Disks up front , drums in back
Changed because I wanted a new chrome one. The one on the car was 50 years old  

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zman123
Everything in my driveway’s a Chevy
Posts: 537
Joined: 06/08
Posted: 07/07/13 06:08 AM

You may want to take the master back off, bench bleed it and start all over. I also got a new (chrome) master cylinder that was bad right out of the box (it happens). I guess the short answer is make sure everything is good before you start. I learn most of my lessons the hard way.  

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idrivejunk
I mow my lawn and find Chevys
Posts: 5119
Joined: 12/09
Posted: 07/07/13 07:14 AM

+1 zman

I think you answered your own question when you said you didn't bench bleed it. You just can't skip that, the master has to be level for the air to escape. You gotta watch closely, too.

Also consult a manual for your vehicle to see if it has a valve somewhere that has to be held open during bleeding.  
idrivejunk

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 07/07/13 11:01 AM

I agree with Matt and Zman. Bench bleed the M/C.
One other thing did you put the rod in the pedal on from the M/C to the brake pedal in the same hole. NOTE: Some brake pedals have a number of different holes that limit travel. The Lever will either add travel or remove it....
One of the Brake companies sell a threaded version so you can tailor the Push/Rod length
Good Luck...

Bob  

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redneckjoe69
I mow my lawn and find Chevys
Posts: 2337
Joined: 03/10
Posted: 07/07/13 12:40 PM

check your wheel cylinders too.    ive seen them blow out a few rare times after a new master cylinder install.       hope you get it figured out.  

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uget2nd
I love my Chevy Chevette!
Posts: 10
Joined: 04/13
Posted: 07/12/13 01:12 PM

Thanks for your input, but I am still having problems.

I did remove the new master and start over.
I bench bled it, not with the hoses that were supplied, but I purchased pre flared brake lines with nuts and bent then into the reservoirs.( 100% no air)
I installed the master, bled the lines in the proper sequence (right rear, left rear, right front, left front) but no pressure at all. Right from the start.
I installed the old master and it had pedal right away, but spongy. Bled the lines and as good as new.

Asked around and found 3 reasons this could be.

1 - Defective master
2- Was sent master for power brakes
3 - Air in system

I know there was no air in the system.
As for the master for power brakes, I rechecked Tuff Stuff model numbers and for a manual brake, 1 inch cylinder, long bore for disk/drum set up    2021NA  part number was correct.( these specs are the same for my old master)
So it must be a defective master. I packed it up, returned it (as defective) and reordered a Tuff Stuff 2021NA (same as previously ordered)
The new one came, bench bled it, installed it and same thing. Absolutely no pedal.
I knew that it wouldn't improve things but I did bled the lines, but nothing

Anyone know whats wrong?  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 07/12/13 03:46 PM

improperly assembled ... by the same group on the assembly line..


well it has 3/8-24 inverted flair ports on both sides...

hmm...


how about some 3/8 inverted flair plugs...   or some 3/8 inverted flair unions and some 3/8 inverted flair plugs..  so you can install them on the end of your bent bleeder tubes..  if you have tube nuts on both ends.  bleed it... then plug the lines.. see if you get a solid pedal...

OPGI and Classic industries both sell in their catalogs... brake pressure gauges that screw into the  bleeder screw holes that would give you the ability to  check both ends of the car to see if the brake pedal motion actually moves fluid and builds pressure..

i might try the 3/8 inverted flair plugs right into the side of the master and bleed them right there..

now.. with inverted flair threads in both sides...  hmm..  some creative person could install short brake tubing sections to a inverted flair to 1/8 or 1/4" pipe thread and a 1000 or 2000 pound gauge directly..  i might do it with a TEE to allow me to bleed the system..


CH28715 Lrg  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 07/12/13 03:54 PM

P7140064  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 07/12/13 04:01 PM

Mascyl


The dual master cylinder splits the brake hydraulic system into two sections, generally serving the front and rear brakes independently.


When the pistons are pushed forward as the brakes are applied, the seals operate against a smooth bore to generate hydraulic pressure. If one side fails, due, for example to a broken brake line, the undamaged side still maintains pressure independently of the failure on the other side. Most of the time the front disk brakes use a bigger reservoir because disk brakes require more brake fluid.

Master cylinders can develop internal leaks caused by seal wear or corrosion of the bore. They may then require double pumping to develop pressure in the effected chamber.  

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