MoparFins

Techical Discussions => General Tech- - BRAKES => Topic started by: Gary Buckley on March 12, 2012, 07:05:10 PM

Title: Poor Brake Pedal
Post by: Gary Buckley on March 12, 2012, 07:05:10 PM
Hi .Can anyone give me a heads up as to what might be wrong that I cannot get a good pedal on my brakes.I have a 1941 Chrysler royal and I purchased a dual mastercyclinder set up from Pirate jacks.I did everything they explained with drum brakes but It still takes about 4 pumps for a good pedal.I have bled the master cyclinder before installing and have bled the system 3 times.I have residual valves front and back I have factory front setup and a 9" ford setup in the rear.The unit I purchased came with the pedal and is designed for under the floor.


Title: Poor Brake Pedal
Post by: Guests on March 12, 2012, 08:02:45 PM
Four pumps indicates air in the lines still.  First thing to do is a visual check for level. All the brake lines need to be lower than the master cylinder itself or it takes a lot of work to get the system bled because air, even as slow as it flows in brake fluid, can be very stubborn to get out of a line that is above the master cylinder, such as where a flex hose attaches to the frame.  Verify there isn't any fluid showing up as a leak from any of the wheel cylinders, that doesn't help, either.  Bleed the front set first, then move to the rear set, use a small rubber hose attached to the bleeder on the back of the bleeder valve and run it into a glass jar, watch  the fluid, you want clear. Use a short hose and put some fluid in the bottom of the jar so you can prove there isn't any air in it, and if the fluid is dirty or has gunk in it, maybe rebuilding the wheel cylinders would be worthwhile. If clean, get bubbless  fluid through and into the small jar and you know it is good. Swap to the opposite side and do the same thing. Prepare to take some time doing this, otherwise, go to Harbor Freight and get a self-bleeding brake pump and follow the directions, it will set you back around $25 last time I heard.
 
Nice car, by the way. Any pictures?
Title: Poor Brake Pedal
Post by: firedome on March 13, 2012, 04:34:33 AM
I always thought you started bleeding the farthest wheel away from the
MC first ie: rear pass wheel, then r driver side, front pass side, then
f driver? Is there a reason why to do it differently on this 41?

Title: Poor Brake Pedal
Post by: Guests on March 13, 2012, 09:25:37 AM
Not a matter of the furthest to the closest, it is a matter of the two halves of the master cylinder (he has a dual master cylinder now), front pair or rear pair. Single master cylinders are as you said because you are attempting to remove the most air from the longest line first.
Title: Poor Brake Pedal
Post by: firedome on March 13, 2012, 09:33:05 AM
D'oh! ... forgot he was converting '41 Royal to dual !

Title: Poor Brake Pedal
Post by: Guests on March 13, 2012, 01:37:39 PM
That's OK, happens to all of us.
Title: Poor Brake Pedal
Post by: Steve on March 13, 2012, 05:29:19 PM


Boy I see the Geriatrics are running rabid here.  LOL
Title: Poor Brake Pedal
Post by: Gary Buckley on March 13, 2012, 08:27:05 PM
Thanks for the info.I pretty well did all the above.Bled throughly 3 times.When I was bleeding them the last time yesterday my son had mentioned that the pedal didnt drop at all when I opened the front bleeders.Some fluid did come out when I loosened the bleeder.I find that most of the pedal when pumped up is Back brakes.The reason being ,When I had my son pumpup the pedal he said that it would go to the floor when I opened the rear bleeder.I also left a pic of my car in a folder Thanks again


Title: Poor Brake Pedal
Post by: Snotty on March 14, 2012, 12:42:06 PM
I had this happen to me once.  After bleeding it 3 times the pedal remained soft as yours is.  Turned out to be the MC, even though it was new.  The (???) valve inside of the MC was bad.  I put another one one and the problem was gone.  Good for me my parts shop did an exchange.
Title: Poor Brake Pedal
Post by: Steve on March 14, 2012, 02:00:29 PM



For the life of me I can't remember what it's called now.
POLARACO2012-03-14 18:01:12
Title: Poor Brake Pedal
Post by: Brian on March 14, 2012, 02:13:41 PM
Residual pressure valve.....That's what your looking  for Steve.(http://www.moparfins.com/forum/smileys/smiley4.gif)  And I'm pretty sure he said he's got one on each line already.


Title: Poor Brake Pedal
Post by: Steve on March 14, 2012, 02:47:32 PM



(http://www.moparfins.com/forum/smileys/smiley36.gif)(http://www.moparfins.com/forum/smileys/smiley36.gif)(http://www.moparfins.com/forum/smileys/smiley36.gif)(http://www.moparfins.com/forum/smileys/smiley36.gif)
POLARACO2012-03-14 18:50:13
Title: Poor Brake Pedal
Post by: Guests on March 14, 2012, 02:47:41 PM
And some just require a whole lot more bleeding than you expect, and just because you get fluid as soon as you open the valve just means air would be higher in the line, or while sitting, the air was allowed to collect at a higher point in the line, so you have to push about three to four ounces through the line to get it right. Don't pump up the brake pedal, that causes bubbles, or makes the compressed air break up and increases the length of time to bleed. Press the pedal, let it do what it is going to do, open the bleeder, close the bleeder, let the pedal up, press the pedal, repeat. After about ten times, note if the pedal is improving, then swap wheels.  After the second wheel, swap to the opposite end and do the same.
Title: Poor Brake Pedal
Post by: Steve on March 14, 2012, 02:52:29 PM


I always gravity bleed for a few hours.  I
Title: Poor Brake Pedal
Post by: Guests on March 14, 2012, 03:10:29 PM
He has a floor master cylinder which may be lower than the wheel cylinders, or lines above the master cylinder level, so he has to bleed a little longer and gentler if he is having problems. One of those brake suction guns may be necessary to overcome any possibility of a bubble being held in the middle of a high point of a line and not able to pump it out gently.
Title: Poor Brake Pedal
Post by: Steve on March 14, 2012, 04:11:33 PM


It's in line with. the wheel cylinders.  But their are bends that go up slightly.  Did I mention I jack the ends up if needed? (http://www.moparfins.com/forum/smileys/smiley2.gif)
Title: Poor Brake Pedal
Post by: Guests on March 14, 2012, 04:43:46 PM
Anything to help in the initial bleeding correctly.
Title: Poor Brake Pedal
Post by: Gary Buckley on March 18, 2012, 06:51:17 AM
Hi everyone .Well I have tried bleeding again.As suggested I bled the system using the no pump theory and at the same time I elavated the vehicle in favor of the master cyclinder as its under the floor.When bleeding I noticed that I had some pedal in the rear because of the pedal dropping when opening the bleeder screw.No air came out with ten bleeds per right wheel.I then proceeded to do the same on the front .When opening up the bleeder screw here I have fluid coming out but almost just a gravity flow and no rush of fluid.Also no pedal drop after ten bleeds per wheel.At the end of the bleeding session i have no more pedal than before and noticed no air coming out.When I had the front drums off adjusting the front shoes ,I noticed that there are very large wheel cyclinders on the front.Is it possible that they are too big for my master cyclinder I purchased? The rear Ford cyclinders are normal size compared to the original 1941 Chrysler cyclinders on the front.Thanks again


Title: Poor Brake Pedal
Post by: Gary Buckley on March 18, 2012, 08:39:30 AM
Hi Again.I just measured the original mastercyclinder bore and it is about 1 1/8 inches in dia and the stroke is an inch.I will have to jack the car up later and measure mine .I know my stroke is only 1/2 and inch for sure.




Title: Poor Brake Pedal
Post by: Guests on March 18, 2012, 12:39:26 PM
That's how my Nash is set up and the rear brakes will lock up easily if too much pedal is given, so a porportioning valve will be needed to fix that. At his point I would consider there being a problem with the master cylinder itself. If you are pushing fluid all the way through without any air coming out, not enough fluid seems to be pressurizing.
 
Do check one thing, that the brake lines are being routed so the front reservoir is going to the rear brakes and the rear one is going to the front brakes, and does this thing have a porportioning valve incorporated into it?
Title: Poor Brake Pedal
Post by: Gary Buckley on March 18, 2012, 04:50:20 PM
At this time I am awaiting an answer from the company that I purchased the brake system from. In their diagram they show drum to drum with a dual master,with the Line closest to push rod feeding rear brakes.The info I read online says that a firewall mounted dual master line closest to push rod feeds front.Another article I read says that a master cylinder used for drum to drum has equal compartments and doesn't make any difference,not like one designed for disc to drum .Also they recommend using a metering valve with the drum to drum insed f a proportioning valve.I really don't know at this time what I purchased.It came from Pirate jacks and was a complete pedal included assembly.I have it plumbed now that the line closest to the push rod is going to my front.


Title: Poor Brake Pedal
Post by: Guests on March 18, 2012, 05:04:09 PM
Agree with waiting for the company to tell what is what, being reverse may have been plumbed differently, but either way it should still be able to get pedal, backwards or not, function is still function, it would be porportions that would be wrong, but pressure should still work. As far as the metering valve goes, with the larger and smaller wheel cylinders, that is to balance front and rear more accurately, because you want about 60/40 front to rear, and the different sized cylinders at the wheel will require adjustment to get that proper. Still doesn't explain why you can't get any brake pedal after bleeding unless the plunger inside the master cylinder itself is bad.
Title: Poor Brake Pedal
Post by: Gary Buckley on March 18, 2012, 05:37:38 PM
I removed the boot tonight from the dual master and got my wife to push on the pedal.It is pushing the plunger in between 1/2 and 5/8 of a inch and bottoms out.The cylinder seems to be about 7/8 to 1 "in Dia. Its hard to get a good visual on it being where it is.After about 4 pumps I have not a bad pedal but it wont last.Next time I push it down it is low again.


Title: Poor Brake Pedal
Post by: Guests on March 18, 2012, 05:57:15 PM
That would be leaking cups in the master cylinder itself, they pump up and are able to overcome whatever is letting the fluid pass by the cups inside, sometimes actually able to push the fluid that passes behind the cups back to the correct side, then leaks back when sitting.

To give an idea, my Dad rebuilt the master cylinder on my TR4 because the brake would do this. I found out years later that there were two size cups, .010 difference in cup size, .740 was early, .750 was the next year (1964), but look identical on the outside, and his rebuild had the smaller cups. The brakes would hold, but as you held them, they would bleed down slowly, but always stopped quickly the first time, so I kind of lived with it and never had a problem. Yours seem to be doing the same thing, but the fluid is actually leaking down right off the bat and require four pumps to correct the problem.
Title: Poor Brake Pedal
Post by: firedome on March 19, 2012, 04:05:57 AM
I've had bad m/c brand new out of the box. For some reason they seem to have a high failure rate.

Title: Poor Brake Pedal
Post by: Gary Buckley on March 19, 2012, 03:08:23 PM
I was contacted by the supplier today and they told me the MC does not have residual valves built in.He said where I am using it as non power brakes that it can be used for drum to drum,drum to disc or disc to disc.I asked him if it had a proportioning valve  and he didn't answer that.I went out today and switched the two lines around on the MC.For some reason I feel like the brake pedal has more travel now.I took the car for a run around the block and it will definitely pump up to give me a good stop.I am going to bleed the circuit again maybe tomorrow evening because I probably picked up some air
 when I had the lines off even though I didn't lose any fluid.I also removed the cover from the MC and slowly pushed the pedal down a few times .There was hardly any movement in the front section but the rear which would be a normal front on one mounted on the firewall erupted 4 inches when slowly pushing on the pedal.Not sure what was happening here as I was just experimenting.


Title: Poor Brake Pedal
Post by: Gary Buckley on March 19, 2012, 03:08:35 PM




Title: Poor Brake Pedal
Post by: Gary Buckley on March 19, 2012, 03:12:25 PM
I forgot to mention that my MC has 2 same size sections.Not sure where there is really any difference from front to back when installing lines but I switched to the way the company I purchased from showed in there instructionshttp://www.piratejack.net/index.php?option=com_content&view=article&id=11&Itemid=18 (http://www.piratejack.net/index.php?option=com_content&view=article&id=11&Itemid=18)


Title: Poor Brake Pedal
Post by: Guests on March 19, 2012, 03:24:23 PM
You say the eruption of four inches spraying fluid happened when you PUSHED  the brake pedal? That isn't right, it is when the pedal is let OFF that the fluid sprays because of the pressure from pressing the pedal and hydraulic pressure. It is backwards, which could indicate one of the plungers was installed backwards possibly, or leaking past the cup and pushing fluid up this way. Here is something you can do to test the master cylinder
 
If brake fluid bypasses a pressure seal on a master cylinder you will get a pedal that fades. To test for this obtain two inverted flare plugs at an auto parts store and plug both master cylinder outlets. Try your pedal. If the pedal is high and firm the master is good. If the pedal fades the master is bad. Replace master as necessary.
 
If in doing this test the pedal slowly loses pressure, it is leaking past the cups.

Title: Poor Brake Pedal
Post by: Steve on March 19, 2012, 04:54:34 PM


I disagree on the residual valves.  A Prop valve is a good idea.  They make adjustable ones.  It gets cut into the rear line.  DO NOT UDE COMPRESSION FITTINGS.  Saying that just in case
Title: Poor Brake Pedal
Post by: Gary Buckley on March 19, 2012, 06:34:28 PM
Yes When I pushed the pedal down the fluid in the section farthest away from the push rod erupts.The section at the push rod end really does nothing noticeable other than a slight movement in the fluid.I really didnt know what to expect with the cover off  while pushing in on the pedal slowly.So when you push on the pedal should the fluid level go down and when you let off should the fluid return as he did when erupting ?Does having he cover off effect how the brake MC works?


Title: Poor Brake Pedal
Post by: Gary Buckley on March 19, 2012, 06:36:15 PM
My shoes have one cylinder  at the top.


Title: Poor Brake Pedal
Post by: Guests on March 19, 2012, 06:56:41 PM
There is a small hole located at the bottom of each of the reservoirs. When the pedal is pushed, there is a rubber piston that pushes and closes this hole after less than quarter inch of movement and is able to pressurize the fluid to the brake cylinders. Since it is full of fluid, along with the wheel cyinders and lines, That piston is compressing about 3/4 an ounce of fluid (thus pumping the brakes for low pedal is able to pull more fluid back into the plunger piston faster than the brakes can allow it to bleed out, thus more pedal power, which bleeds off when the brake is not pushed after a few seconds naturally). OK, now, when you back off the pedal (under normal conditions), there is fluid that fills in behind the piston through this hole, and when you back off the brakes, that fluid is forced out the hole because of the 1200-1500psi pressure from the brake pedal fluid, thus is squirts, but slows down the pedal speed because the hole restricts the brake fluid speed and keeps things from breaking after a few months of this, but it should squirt when the brake is released, not when it is pressed. This indicates something is WRONGGGGGGGG. In thinking about this and rereading what you are saying, the front piston has some kind of damage, backwards, part missing, because the rear pressurizing plunger is somehow putting pressure against the front cylinder and I bet if you did it often enugh you could actually transfer fluid from the one non-squirt reservoir to the other reservoir. Look at a blow-up assembly in your link of the master cylinder and you will see two sets of plungers, some separators and springs that work together (sometimes different diameters) and how they both push fluid with equal pressure but can do different volume (disc take larger volume, so being located on the front it would be a bigger piston/cup and the rear would be smaller so they work correctly to brake evenly), but yours for some reason isn't doing that, it is pushing fluid from the rear to the front and it shouldn't.
 
Does that help?
Title: Poor Brake Pedal
Post by: Gary Buckley on March 20, 2012, 04:42:33 AM
Thanks for the info.When I bench bled the MC it seemed to be fine so I guess something has gone wrong.I will pull it off and take it apart.


Title: Poor Brake Pedal
Post by: Steve on March 20, 2012, 04:51:06 AM


Single.  Yeah I forget some of the incidentals
Title: Poor Brake Pedal
Post by: Gary Buckley on March 21, 2012, 06:51:58 PM
Ok people I am back.Today I think I gained some ground with the beast. First thing I did was block off the 2 lines on my MC and it passed  with flying colours.Pedal was at the top and never dropped any amount so I am now ruling out the master.I removed the right front wheel to inspect the brake lining and check to see if I was running out of travel on my shoes.The lining is defenitely down over half way so I will be ordering new shoes .I noticed one of the rubbers on the wheel cylinder was damp so I released the one spring and the pins that hold the shoes on and let them swing away from the cylinder .When I did this I noticed another set of adjusting cams hidden behind the shoes.Which was great to find.I removed both rubber boots from the cylinder and found both ends were leaking.I removed all the rubbers and spring .Checked them thoroughly ,cleaned everything up and reassembled everything .I then removed the drivers front and checked it out .No leaks and the shoes are getting close to the rivets towards the top as the passengers side were.Once I had the wheels back on I adjusted the front shoes more than I did the previous day using the top adjusters this time.I proceeded to get my wife out and do some bleeding.Using the one pump method that was suggested I bled all wheels.I bled the rear 10 times per wheel and the pedal stayed very low but you could hear it drop when I opened the bleeder.I next bled the left front ,the same amount of 1 pump per bleed.Some air cam out but not alot.At this point we still didnt have any pedal.I then proceeded to the right hand front.After 2 bleeds fluid finally came out.Instantly my wife yelled out that she had a good pedal.I continued to bleed until all air seemed gone and then topped off both sections in the MN again.Now when I hit the pedal  I have quit a bit and with the second and third pump it just gets better.1 pump I can hear front and back shoes moving so I think I may have this beast whipped .Pedal feels spongy as it did last summer driving with the original running gear and rear housing .I am going to order a kit for the 2 wheels cylinders and some brake lining just the same.I want to thank everyone for their input it was greatly appreciated.
.




Title: Poor Brake Pedal
Post by: Gary Buckley on March 21, 2012, 06:55:24 PM




Title: Poor Brake Pedal
Post by: Gary Buckley on March 21, 2012, 06:58:36 PM
By the way regarding the brake hoses.Yes I replaced every hoe and line on the car this winter.The only used parts are the front brake shoes and the 2 front wheel cylinders.When I installed the 9" ford housing I replaced everything on the housing except the backing plates which were in great condition.I will try and download some pics to give you guys some idea of the work I did in the last 4 months


Title: Poor Brake Pedal
Post by: Guests on March 21, 2012, 06:59:04 PM
We ain't done yet, but at least going through procedures you learned a lot, learned how to adjust brakes (and check a master cylinder, which I am glad to hear it is OK), and know what needs fixed on top of everything else. Keep us informed, you have a good start to being able to cruise in a week or so!
Title: Poor Brake Pedal
Post by: Gary Buckley on March 21, 2012, 08:08:41 PM
Ok I posted some picks of the last 4 months .I was a busy beaver this winter.I uploaded the pics to my profile I am not sure if everyone can see them or not .let me know if you cannot and I will move them to whatever the moderator tells me to i guess thanks again