Spongy brake pedal

Carla · October 17, 2010, 07:35:05 PM

Quote from: Plymouths on August 13, 2010, 05:44:41 PM
Before going to all the work of removing the master cylinder, only to find out it's not your problem, I would try some trouble shooting first. Make up a fitting of a piece of pinched tubing and nut to go on the master output line to the shoes. This will fool the master into thinking all the brake shoes are out and touching the drums. Any application of brake pedal should be 'hard' with very little movement. When you remove the output line to the brake you will dump all the fluid in the system uphill from that point BUT this test may prove out whether or not the master is the fault. When you have the blocked test line on it's only a matter of filling the master reservoir to maybe 1/2 way. You will see bubbles coming up through the refill holes as you put in the brake fluid. This is the piston area filling. When they stop you have a full piston chamber. Pushing the brake pedal should be almost impossible.

If you try this particular test, then any further movement of the brake pedal after you have applied full pressure, that is, any sinking of the pedal under pressure, should be literally 'impossible'. If, under such a test, the pedal were to 'sink' at all, that would indicate leakage around the cup within the master cylinder and/or pitting in the master cylinder bore.

If you are at all uncertain about a master cylinder, have it out, hone the bore gently, and inspect it carefully. If any pitting does not completely clean out at .010 over standard size, replace the cylinder, or send it to a specialist firm to have it sleeved.

Its always prudent to have the master cylinder out, clean it up, and give it a good close inspection, looking for any pitting in the bore or wear to the cup, and honing/fitting a rebuild kit as may be necessary, if you haven't personally done this, or know of that work certainly having been done in the reasonably recent past. This is a rather serious road safety issue, actually....... : )

cheers

Carla

RC Drown · September 15, 2010, 03:17:03 PM

Bob,

Good news my friend, now get out there and drive the heck out of her, she will appreciate it:):)

41PlySD · September 15, 2010, 01:30:05 PM

Update: I have carefully adjusted each brake shoe set out to where the shoes locks the drum then backed off leaving a fair amount of drag. Before I left little to zero drag. Rears are much harder to judge and I did have the left rear too tight for a while but have since backed it off a bit. Anyways...brake pedal is up pretty good now and seems to get better as I drive it. I've also replaced the e-brake band so I feel much safer when I drive the car now. E-brake works pretty well now. I'm actually starting to have a lot of fun in the 'ol green tank...Thanks again for all your advice guys. It certainly helped me out A LOT!

Bob

Don St Peter · August 28, 2010, 02:18:51 PM

Make sure the small hole in the bottom master cylinder is not plugged. Also make sure the brake pedal adjustment is correct soas to not obstruct the master cyl. hole.
Don

elmo · August 14, 2010, 04:51:43 AM

plymouths ,
how do you fool an inate ?(not sure if this is the right word )object its 1930,s 1940,s, 50,s plus technoligy , if it was later and computor techs you could fool it . i have owned and have been driving and repairing chrysler product cars since about 1960 , if your brake pedal is spongy its definately air problems , if it creeps? to the floor boards under pressure its a leak in the system , if it travels to low to the floor boards but is firm when it gets there its an adjustment problem , or the linings need replacement . there is one other comment different people have different views of what spongy actualy is
. Rex

41PlySD · August 13, 2010, 10:41:34 AM

Quote from: MRR41 COUPE on August 12, 2010, 08:31:43 PM
Just a note, If you remove any of your brakepads or remove a pad spring or maybe even do a major outward adjustment you will have to bleed that wheel cylinder. I had my system adjusted perfect but then I removed a pad and put it back on. I did not think the wheel cylinder move but to my surprise my line had air in it and the pedal travel went bad. I pressure bled the one wheel and everthing worked great.
Please don't drive with bad brakes, Thats deadly for you and gives the hobby a bad name. We don't need any more laws passed to make our hobby harder for us. Drive safe and have fun.
Mike

That's good sound advice Mike...Thank you. I definitely need to get whatever is wrong fixed before I get her out again. I'm ready to pay someone to fix it...just don't have a trusted mechanic.....yet. Thanks again, Bob

MRR41 COUPE · August 12, 2010, 08:31:43 PM

Just a note, If you remove any of your brakepads or remove a pad spring or maybe even do a major outward adjustment you will have to bleed that wheel cylinder. I had my system adjusted perfect but then I removed a pad and put it back on. I did not think the wheel cylinder move but to my surprise my line had air in it and the pedal travel went bad. I pressure bled the one wheel and everthing worked great.
Please don't drive with bad brakes, Thats deadly for you and gives the hobby a bad name. We don't need any more laws passed to make our hobby harder for us. Drive safe and have fun.
Mike

CHS · August 12, 2010, 02:05:19 PM

CONGRATULATIONS, on your new acquisition! Happy motoring.
As for the brake problem problem. Make sure you have a good emergency brake just incase. I would make sure the brakes are in good working condition before driving the car.

41PlySD · August 12, 2010, 01:45:17 PM

Hello to everyone...I've been away on a "quick" vacation...Just "had to" go down south to look at another car. I wound up buying it because it was so nice...a 57 Plymouth Belvedere, desert gold and sand dune beige...just like the Tulsa Plymouth...Miss Belvedere! Since I got back I've been arranging for her delivery. I'm sittin on the dge of my seat here! 8)

Anyways back to issue at hand...I have not done a thing on the 41 brake issue since I pressure bled it. I had it out the other night to go get a pizza. I tell ya...what a fun ride that little 'ol 41 is!...even with spongy brakes. I'd love to get this problem figured out but I know the next step should be to remove the front seat...remove the front floor pan and get in there to rebuild/replace the master cylinder. I just might wait until the heat/humidity go away...and even maybe wait until the late fall so I don't lose any more drive time. At the same time, I don't want to drive it too much like it is (bad brakes) either. To sum up the whole situation....I'm reasonably sure I have the shoes adjusted correctly...I've been around the car twice tightening and backing off the upper cams....on the fronts (because I had the shoes off to replace the wheel cylinders and hoses) I'm reasonably sure I have the lower cams adjusted properly as well. I bled the system twice...the second time with a pressure bleeder that I fabricated so I'm reasonably sure there's no air in the system. The brake pedal engages the brakes at ~ 1/2 way down and then it's spongy alll the way to the floor...every time. The car stops but I wouldn't want to have to stop real quickly. When I pump the brake pedal it never gets hard...always stays just as I just descibed it. If anybody would like to comment on what I believe my next step should be...please do...Thanks everyone!

Bob

mvair · August 11, 2010, 11:13:38 PM

I don't know if it is true but I have been told that sometimes there is a bubble in the brake line where it arches over the differential that can be difficult to remove even with a pressure bleeder. No solution other than to try and push it out with a constant pressure for a few seconds. I was also told that without constant pressure it will float back to the top of the arch between brake pumps. Like I said, this is only hear say.

JimCno · July 31, 2010, 09:27:05 AM

Well it sounds like you've done everything right. You never did mention if you had adjusted both the major and minor cams. If you've done the bleeding and adjusting and still have the problem I have no more ideas other than to take it to a shop that understands these old brake systems.

my33ply · July 30, 2010, 08:50:14 AM

I'm certainly no expert on brakes, but I had an experience where the lining had a slight space between it and the shoe. When the brake was depressed the space acted as a cushion and caused a "spongy" feel. When you discover the cause please let us know. Good luck! ???

41PlySD · July 29, 2010, 09:58:36 PM

Used my newly made pressure bleeder today...bled all 4 wheel cylinders....Let them squirt for quite a long while each...no bubbles came out at all. No change in pedal...still spongy. This is getting real old real quick :'(

Bob

FourDoor · July 29, 2010, 10:23:42 AM

I've also taken a piece of wood and jammed it between the driver's seat and the brake pedal to push the pedal down and use the cushion 'push' to load the pedal. Then I go to the brake wheel cylinder and crack open the bleeder screw watching in the clear plastic tubing for the air bubbles to stop. Always of course returning to the master to make sure it's topped up. I prefer to remove the top of the master to make it easier to see into the reservoir and also fill it without any spillage. Brake fluid is a really good paint remover.
This works well for doing a repair on one wheel cylinder and you're by yourself. Slow as molasses to do a complete brake job but it can be done.

MRR41 COUPE · July 28, 2010, 09:37:24 AM

As long as you have brake fluid in the master cylinder, the bubble will stay on the top and the fluid on the bottom.

41PlySD · July 27, 2010, 11:24:56 PM

No one answered this question I previously asked...I built a pressure bleeder but now I'm wondering...When pressure bleeding the master cylinder, what about the air bubble on top of the fluid...Does that have to be removed? Not sure how one could do that? Otherwise you're pressing fluid into the master cylinder on top of an air bubble. That seems like it would create a vapor lock...

Thanks, Bob

JimCno · July 27, 2010, 12:43:41 PM

Quoteas a matter of fact, the pedal still goes to the floor...but car does stop

Again... The pedal going to the floor is usually an indication that the shoes need adjusting. As John H. said, a little "zing" is not unusual. You mentions adusting the top cams (Major adjustment) but not the bottom cams (Minor adjustment). Follow this link for a abrake adjusting procedure chart. http://www40.addr.com/~merc583/mopar/p15pdf/brake.pdf

If you press the pedal down, the brakes are applied, and you can press the pedal further, that is a "spongy pedal". That indicates there is still air in the system. If there is a leak somewhere, it can get in that way. If you've sealed all the leaks with your new hardware then there is an air bubble that hasn't been removed yet.

The proper procedure for bleeding brakes is as stated before, is to start at the cylinder with the longest distance to the MC and working back to the cylinder with the shortest distance (LR-RR-LF-RF). I've heard of a bubble getting stuck where the rear brake line goes over the top of the "pumpkin".

QuoteBottom of reservoir looks dirty....brown/rusty murky fluid was in there...Still seems to be a film down in there but the addition of new fluid has cleared it up a little.

All your brake fluid should be clear. If not, you should flush it until it is clear.

Here is a link to a technical bulletin that covers our brake systems in detail.... http://www.imperialclub.com/Repair/Lit/Master/008/cover.htm

Take your time, examine your problem, do you have a low pedal, a spongy pedal or both. Get it right as there is nothing more important than having good brakes when you drive your car.

Good luck, I hope this helps.

John Hendricks · July 27, 2010, 11:08:03 AM

I am by no means an expert on braKES, but i have found if u adjust the shoes so there is a very faint Zing from each shoe as u spin the wheel, u have it about as good as it is going to be. Theoretically one should not hear that ZING but the system is not perfectly round.

elmo · July 27, 2010, 03:01:08 AM

theres nothing wrong with pressure bleeding if you have the gear to do it , i,ve done it my self , the main thing in bleeding the brakes on a plymouth or any early chrysler product car , is start at the cyl furtherest from the master cyl . in your case with a LH drive car , bleed the right rear , then left rear , right front , finaly the left front . if your pedal is spongy ! it has nothing to do with adjustment , theres air in the system.

41PlySD · July 26, 2010, 11:07:29 AM

Quote from: JimCno on July 26, 2010, 10:26:34 AM
It sounds like you may have two problems.

Spongy pedal, which means their is still air in the lines and low pedal which means you need to adjust the brake shoes to ride closer to the drum.

Just to clarify the terms, I've heard people use the term "Spongy" when they had to pump the brakes to get them to act on the drums and that sent them down the road to bleeding them when they should have been adjusting the shoes.

Just wanted to put that out there.

Well Jim, I have adjusted the brakes the best I know how...I turned the upper cams bolts on the back of each wheel until the shoe dragged on the drum then backed it off slightly until there was no drag...Should I be leaving some drag? I was afraid to leave some drag because I didn't want to heat up the drums/unnecessarly wear down the shoes while driving. Please let me know. Thanks...Bob

Also...When pressure bleeding the master cylinder, what about the air bubble on top of the fluid...Does that have to be removed? Not sure how one could do that? Otherwise you're pressing fluid into the cylinder on top of an air bubble. That seems like it would be a vapor lock...

JimCno · July 26, 2010, 10:26:34 AM

It sounds like you may have two problems.

Spongy pedal, which means their is still air in the lines and low pedal which means you need to adjust the brake shoes to ride closer to the drum.

Just to clarify the terms, I've heard people use the term "Spongy" when they had to pump the brakes to get them to act on the drums and that sent them down the road to bleeding them when they should have been adjusting the shoes.

Just wanted to put that out there.

41PlySD · July 25, 2010, 09:58:15 AM

Quote from: Go Fleiter on July 25, 2010, 06:28:25 AM
Sure! We enjoy Your pics!
Beautiful cars in beautiful surrounding!
Where do You live?

Greetings from D?sseldorf! Go

Glad you enjoyed the photos Go!...I live in the Rochester, NY area...about 6 miles from the south shore of Lake Ontario.
Thanks for your continued encouragement Bob...You have been great! I sure do appreciate it....Pat, after I build my pressure bleeder if there's no improvement, I will remove the floor pan (again :() and try adjusting that push rod. I always like to have "several things to try". It's when I run out of things to try...then I quickly get frustrated...So thanks for all the ideas guys...I really really appreciate them!

Bob

36 Ply · July 25, 2010, 09:26:22 AM

Bob,

If nothing else works for you, you might try playing with the adjustment on the master cylinder pushrod. A long time ago, I installed a new master cylinder in my (former) '36 4 door. I found that 1/16 to 1/32 inch difference in the pushrod length was the difference between a decent brake pedal and no pedal at all (went to the floor).

Good Luck,

Pat O'Connor

RC Drown · July 25, 2010, 07:04:40 AM

Bob,
I have talked to Buddy on the phone a number of times. He keeps me updated on the progress of his '40 Plymouth via emails. A friend of mine had a pressure bleeder so we used his on mine. Thanks for sharing the photos and glad that you were able to put some miles on her yesterday.

Go Fleiter · July 25, 2010, 06:28:25 AM

Sure! We enjoy Your pics!
Beautiful cars in beautiful surrounding!
Where do You live?

Greetings from D?sseldorf! Go

41PlySD · July 24, 2010, 11:10:44 PM

Thank you very much guys for all the advice....Buddy Romines PMed me...we talked and he told me the same thing. "Pressure bleeding is the way to go"...He even offered to send me his pressurizer...Sure is a nice guy. RC Drown was right there too sharing his 40 brake work with me too. I've had nothing but encouragement and support here from many of you. Thank you all so much. I plan on building myself a MC pressurizer this coming week. I'll let you all know how it works out. I took my 41 around the block today...(5 miles) It performed well...spongy brakes and all. I needed that as it's all I've been doing lately is working on it. Needed to enjoy it a little. After that I brought all 3 out side to enjoy and took a few photos ...thought you guys might enjoy...

Bob

MRR41 COUPE · July 24, 2010, 10:14:38 PM

I agree, I had to pressure bleed my brakes on my 41 before they worked, I did have to adjust the pads one last time after they were blead. They work great now, good luck with yours.

Jim Yergin · July 24, 2010, 10:02:47 AM

On my '41 I had trouble bleeding the system until I built a pressure bleeder using a garden sprayer. Here is an explanation of how you make one.
http://www.autofixworld.com/index.php?option=com_content&task=view&id=515&Itemid=91
On my '41, I found a barbed hose fitting that fit in place of the fill plug on the master cylinder and I attached the bleeder hose to it rather than the rubber cap set-up shown on the above referenced site.
Worked well for me and disclosed a leak at the junction on the rear axle. Hope this helps.
Jim Yergin

41PlySD · July 23, 2010, 02:27:35 PM

Ok, Here is exactly what I did so far...to get this spongy brake pedal.

Bought 41 Plymouth in April.
Didn't like that pedal was spongy.
Adjusted front brakes noticed left front wheel cylinder was leaking.
Ordered SS sleeved wheel cylinders from Hagen's Auto Parts in Puywallup, WA
Ordered new front brake hoses from NAPA
Did not completely drain system/installed cylinders and hoses.
Bled fronts first...lots of air came out initially but then strictly fluid only...made sure to keep reservoir topped off.
Wife was pushing down on pedal...kept asking her...Is pedal getting hard? Answer was always no. still is no.
Adjusted rear brakes did "the tighten until wheel stops" then backed off a touch...
Bled out rears 2-3 times each using same method...only fluid squirted out...no air at all
Car does have brakes right now but very spongy.

Observations:

Bottom of reservoir looks dirty....brown/rusty murky fluid was in there...Still seems to be a film down in there but the addition of new fluid has cleared it up a little.
I did not remove floor pan to do this job...I kept the cover off of reservoir during the bleeding process to make addition of fluid easier.
Reached down in there and squirted brake fluid in with a plastic syringe to refill reservoir.
My wife DID press the pedal to the floor...as a matter of fact, the pedal still goes to the floor...but car does stop. I'd hate to have to stop real quick though!

What could be my next step short of removing master cylinder and sending it off to get rebuilt??? I'd hate to lose the rest of the summer!?