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Spongy Brakes
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dels56
Posted 2020-07-11 2:57 PM (#600733)
Subject: Spongy Brakes


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I am pulling my hair out! I have done a brake job on my 56 Dodge, Rear drums, Shoes, Wheel Cylinders... As a mechanic in a Chrysler garage when I was young I did 100's of brake jobs and cannot remember having a problem such as this. Although this is a bit different as I have converted the front to Disc using AAJ components with a 1976 Mopar dual compartment Master Cylinder and 76 Mont Carlo Calipers. I bench bled the master before bolting it in place and plugged the ports until I was ready to connect lines. Once the lines were fitted I again bled the master (picture). Then proceeded to bleed the system. This should give ema good solid peddle but NO SUCCESS! Spongy, like putting you foot in a pail of cow dung.

Any and all suggestions are appreciated.

Del S.



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Viper Guy
Posted 2020-07-11 3:53 PM (#600734 - in reply to #600733)
Subject: Re: Spongy Brakes



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What you describe is like air in the lines that just hasn’t bled out. Assuming you have adjusted your brakes properly, you might try bleeding the lines again until there are no bubbles. The other alternative might be a faulty master cylinder. I’ve had experience there as well. Other than those, I’m out of suggestions but others on here might know or experienced different solutions.
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56D500boy
Posted 2020-07-11 4:28 PM (#600736 - in reply to #600733)
Subject: RE: Spongy Brakes



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Del: My suggestion would be to use your new "T" block to isolate the front brakes from the rear brakes (one end at a time) and thoroughly bleed the fronts and see if it goes away. If not, you know that the issue is the front system. Likewise, if you isolate the rears from the fronts and then bleed the rears thoroughly, then you will have more data. As it is, you have 4 points of bleeding failure that you can't distinguish from one another.

My 2 cents.

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bbdakota
Posted 2020-07-11 5:23 PM (#600737 - in reply to #600733)
Subject: Re: Spongy Brakes


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Definitely sounds like air in the system. I'm gonna ask a stupid question. You didn't get the calipers mixed up and put them on the wrong side did you? The bleeder should be at the top
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dels56
Posted 2020-07-11 5:46 PM (#600739 - in reply to #600733)
Subject: Re: Spongy Brakes


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Thanks for the input. I am in the process of Isolating the front/rear and see what happens. I had to give it up for a while and take grand kids for ice cream.

And the bleed valves are on top.

I will let you know how I make out.
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dels56
Posted 2020-07-14 9:22 PM (#600899 - in reply to #600733)
Subject: Re: Spongy Brakes


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Ran out of fittings to use on isolating front/rear so have to make a trip to the city before continuing. No on to fuel gauge and window alignment and................
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jboymechanic
Posted 2020-07-14 10:19 PM (#600901 - in reply to #600733)
Subject: Re: Spongy Brakes



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Del,

Are you just now installing the disc brake setup and now you're having issues? Or have you had this system in the car for quite some time? When I converted to disc brakes, I had to go one bore size bigger on my master cylinder to get the pedal feel I was looking for, you have to displace more volume in disc calipers than drum cylinders.
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dels56
Posted 2020-07-15 4:04 PM (#600932 - in reply to #600733)
Subject: Re: Spongy Brakes


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Hi Jon, I just installed the AAJ conversion. Actually a while ago but have not had the car out of the garage as yet. AAJ recommended the 76 Dodge Dart master with a 1.031” bore. If I could get it to where I have a solid peddle I could then judge if I need to go to a larger bore, say 1.125” I do not have power brakes so it is tricky to balance bore size and effort.
Del
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jboymechanic
Posted 2020-07-15 11:22 PM (#600954 - in reply to #600733)
Subject: Re: Spongy Brakes



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Roger made the same recommendation to me, but I had four wheel disc brakes (much more volume). I bled, bled and re-bled without getting any air or a better pedal feel. Car stopped, but the pedal went almost to the floor with little effort. I then changed to the larger 1 & 1/8 inch bore MC and then my pedal was just right. I now have that same master cylinder in all three of my plymouths with AAJs front disc brake kits (only one has rear disc, the other are still original drum rear) and I like the stopping and pedal feel in all three cars.
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dels56
Posted 2020-07-16 1:48 AM (#600958 - in reply to #600733)
Subject: Re: Spongy Brakes


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Thank you, I have narrowed it down to being the master cylinder at fault. I will pick up a new master 1.125 bore and give that a try.
Del
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dels56
Posted 2020-07-16 1:56 AM (#600959 - in reply to #600733)
Subject: Re: Spongy Brakes


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John, what brand and part number master cylinder did you use.
Del
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jboymechanic
Posted 2020-07-16 12:13 PM (#600975 - in reply to #600733)
Subject: Re: Spongy Brakes



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Del,

See this thread for some other helpful details from when I did my 4 wheel disc brakes in my 1960 Plymouth 2 door sedan:

http://www.forwardlook.net/forums/forums/thread-view.asp?tid=68713&...

Master cylinder is Raybestos MC39178. I like these for their bore size and they're aluminum with a plastic reservoir. Look out of place under the hood of an old car, but the aluminum doesn't rust up like cast iron and the caps are much easier to open that prying off the wire.

Edited by jboymechanic 2020-07-16 12:15 PM
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dels56
Posted 2020-07-17 9:45 PM (#601022 - in reply to #600733)
Subject: Re: Spongy Brakes


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I have not been able to pick up a new master cylinder with a 1.125 bore, so I proceeded to take the existing master off and take a look at it. I wanted to make sure it had an integrated residual pressure valve. Master id a Dorman MC88787. It does have a 10 PSI residual valve which I tested and it cracks open at 10 PSI air.And for anyone who is interested the ports are; Rear Port (closest to firewall) is for FRONT Discs. Has a 1/2"-20 Inverted flare port. The Front port is for the Rear Drums and has a 9/16"-18 inverted flare port.. The residual valve is integral to this port.



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dels56
Posted 2020-07-21 6:56 PM (#601160 - in reply to #600733)
Subject: Re: Spongy Brakes


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AIR, AIR, AIR,This is getting ridicules. As you can see from the above pic, I have taken the master out and disassembled to make sure all the parts are there and in good condition. 1.031" bore, 76 Dodge Dart as per AAJ. Then I pulled the rear wheels and checked everything there. Front calipers are 76 GM Monte Carlo (single piston) again as per AAJ. Both master and calipers are new not rebuilt. I use a bleeder bottle with fluid in it so no air can travel back into the system. The rears seem to be free of air now after an hour of pumping the peddle. The calipers, crap....I have pumped enough air out of them to float a blimp. My neighbor is the man on the peddle and I get a solid line of fluid until the peddle reaches near bottom of travel, then I get a burst of air bubbles. Where the hell is the air coming from and how do I get rid of it????
p/s. bench bled master, 120 strokes or more???

Note; I bought the best darn double flare tool for 3/16" lines ever. Titan, works slick as....

Edited by dels56 2020-07-21 7:08 PM




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56D500boy
Posted 2020-07-21 7:07 PM (#601163 - in reply to #601160)
Subject: Re: Spongy Brakes



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Stupid comment: While you neighbour is slowly depressing the pedal, how are you keeping the reservoirs full so air isn't getting entrained?

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dels56
Posted 2020-07-21 7:11 PM (#601164 - in reply to #600733)
Subject: Re: Spongy Brakes


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Running up and down a ladder and checking every 10 pumps. I"m getting old and those steps are hard on an old guy.
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71charger_fan
Posted 2020-07-21 10:07 PM (#601169 - in reply to #600733)
Subject: Re: Spongy Brakes


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On my '55 Plymouth I had the same problem. I pinched off both front hoses and the hose to the rear axle and had a solid pedal. I released the clamps on the front hoses one at a time, checking the pedal after each clamp was released and I still had a good pedal. So I released the clamp on the rear hose and got a spongy pedal. After replacing the rear wheel cylinders twice and bleeding many quarts of brake fluid, I still had air in the system. I eventually bought a handheld pressure bleeder and tried pushing fluid across the rear axle brake line from one side to another with the hose clamped off. Once I pushed fluid into the wheel cylinder with the drum off and let the shoes move in and out a few times, a stubborn air bubble finally let go and came out of the wheel cylinder.

http://www.forwardlook.net/forums/forums/thread-view.asp?tid=63722&...
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dels56
Posted 2020-07-22 7:20 PM (#601188 - in reply to #600733)
Subject: Re: Spongy Brakes


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I blocked lines off today and can push peddle to the floor...nothing. Probably could have plugged port on the bench but then probably not enough leverage to push piston in. New master going on Saturday.
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71charger_fan
Posted 2020-07-22 8:22 PM (#601194 - in reply to #600733)
Subject: Re: Spongy Brakes


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I finally had to get port plugs as I was plagued with defective master cylinders. With the master bench bled, installed, and the ports plugged, I could easily verify that the master was good.
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56D500boy
Posted 2020-07-22 9:22 PM (#601197 - in reply to #601188)
Subject: Re: Spongy Brakes



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dels56 - 2020-07-22 4:20 PM
I blocked lines off today and can push peddle to the floor...nothing. Probably could have plugged port on the bench but then probably not enough leverage to push piston in. New master going on Saturday.


So that implies that the piston bore is too big or the piston seals are too small (or both). Fine Chinese crapsmanship?

Good luck Saturday.

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56D500boy
Posted 2020-07-22 9:27 PM (#601198 - in reply to #601188)
Subject: Re: Spongy Brakes



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dels56 - 2020-07-22 4:20 PM
I blocked lines off today and can push peddle to the floor...nothing. Probably could have plugged port on the bench but then probably not enough leverage to push piston in. New master going on Saturday.


So that implies that the piston bore is too big or the piston seals are too small (or both). Fine Chinese crapsmanship?

Good luck Saturday.

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dels56
Posted 2020-07-22 10:56 PM (#601207 - in reply to #600733)
Subject: Re: Spongy Brakes


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Current master is a Dorman M88787. I ordered a Raybestos. They look the same so maybe both the same craftsmanship. Maybe Raybestos has better quality control. If this doesn’t work, does any have a spare anchor?
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56D500boy
Posted 2020-07-24 12:47 PM (#601251 - in reply to #601198)
Subject: Re: Spongy Brakes



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56D500boy - 2020-07-22 6:27 PM
dels56 - 2020-07-22 4:20 PM
I blocked lines off today and can push peddle to the floor...nothing.

So that implies that the piston bore is too big or the piston seals are too small
:)


This whole thing dregged up a long forgotten memory of me and my 1955 Dodge in 1967: My dad had given me the 1955 Canadian Dodge (Plodge) Regent (Belvedere side trim but 6 and 3 spd manual) in the fall of 1966 when he bought a 1965 Plymouth Fury III V8 torqueflite sedan. I was 15 so I couldn't drive it officially until the spring of 67 when I turned 16 (I had learned to drive it when I was 12 on the back roads outside Regina).

Ten days after turning 16, I had my license and started driving to high school (Grade 11). Not sure when I noticed it, but I did find that I needed to pump the brakes to get a good pedal to stop and also that if I left my foot on the pedal while parking (knudge, knudge, wink, wink) the pedal would go to the floor. I didn't mention this to my dad and just coped with it.

Then one day, I had to drive to Saskatoon to attend some kind of pre-university math "camp" at the University of Saskatchewan. I didn't get very far out of Regina when a cop (RCMP) spotted me driving north on Hwy 11 (he was driving south) and spun around and chased me down and pulled me over. In his defence, while I wasn't speeding or anything (that would come years later), I did look about 12, maybe 13, behind the wheel. Finding nothing seriously wrong, he proceeded to check the car out, looking for a reason for the stop. Eventually, he gets to the brakes and finds that the pedal will go to the floor with constant pressure. He let me go with a warning ticket which required me to repair the brakes and report back to the detachment in Regina within 10 days (or so). I proceeded on to Saskatoon for the weekend and then back home without any issues.

Once home, I showed the ticket to my Dad who had me go down to a local jobber and buy a master cylinder kit for the Dodge. Armed with that, my Dad taught me how to hone/clean the master cylinder bore and replace the piston cup, seal, etc. (which I think was leather). I remember doing that but I don't really remember much else. For sure, no bench bleeding, just regular wheel cylinder bleeding, etc. When it was done, I took the receipt for the parts to the "cop shop" (Mounties) and they voided the ticket. So that was 1967 (or maybe the spring of 68). So 52 or 53 years ago.

I only learned about bench bleeding 4 years ago when I installed a new Raybestos master cylinder on my 56 Dodge Custom Royal in the first months after I bought it.

To this day, when coming to a stop, I still pump the brakes a bit, in every car that I drive, to make sure that I have a good pedal.

Good luck with your new Raybestos dual channel MC.





Edited by 56D500boy 2020-07-24 2:21 PM
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Powerflite
Posted 2020-07-24 2:09 PM (#601252 - in reply to #600733)
Subject: Re: Spongy Brakes



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I've had issues with brand new Chinese made '73 Dart masters too. I think you're better off buying rebuilds. That's what I do now.
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ram300
Posted 2020-07-25 5:41 AM (#601279 - in reply to #601252)
Subject: Re: Spongy Brakes



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I've just had issues with a new dual m/cylinder wouldn't bleed up at all well, very spongy pedal, infuriated with it I took the '57 NYer for a hard run and stop test drive and by the time I got back to the shop the pedal was close to the floor, still stopping the car but horrible mushy pedal feel.

Pulled the m/cylinder cleand and replaced all the rubber bits, bench bled then back on the car, hard pedal didn't even need to get under it.

In my case it was either dud seals OR I'm running dot 5 silicone fluid and it reacted in some way with the assembly lube the manufacturer used. From now on I'm pulling new m/cylinders apart and thoroughly cleaning then reassembling with dot 5 prior to installation.

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56D500boy
Posted 2020-07-27 3:01 PM (#601402 - in reply to #601188)
Subject: Re: Spongy Brakes



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dels56 - 2020-07-22 4:20 PM I blocked lines off today and can push peddle to the floor...nothing. Probably could have plugged port on the bench but then probably not enough leverage to push piston in. New master going on Saturday.


So? Spongy or not spongy?

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dels56
Posted 2020-08-02 1:50 PM (#601603 - in reply to #600733)
Subject: Re: Spongy Brakes


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OK people, chime in here. I am at a loss! I have checked and rechecked every component and adjustment, now on my second new master cylinder. As I wait for a new fitting for the rear brake port (front compartment) in the master, I put my bleeder hose from that port to the reservoir as if I was simply bleeding the master. Then I gravity bleed the front callipers...again. Flows like water with not a trace of a bubble. Left first then right side. Instructions with the m/c say not to bottom out the piston so I marked the push rod in 1/4 inch increments. I can now push the peddle to the 1-1/4 “ mark using my hand and nothing. And I mean nothing. I have gently pushed the peddle as far down as it goes. I have someone else slowly push the peddle while I open a bleeder screw and I have a squirt of clear fluid. I cannot believe 2 faulty m/c’s and I am sure AAJ has confirmed many times over that the 1.031” bore is enough to fill the callipers.



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Powerflite
Posted 2020-08-02 5:47 PM (#601611 - in reply to #600733)
Subject: Re: Spongy Brakes



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You have to diagnose it. Narrow down the possibilities. It's impossible for us to do from our computers. I did have a caliper that had been repaired with a helicoil at the plug, that wouldn't seal. So if your calipers have a helicoil in them too, exchange them with different ones. Make sure there is no trapped air in your splitter valve too. If you plug the top side of it with a line, that line could hold a pocket of air that you would never be able to bleed out. But you will need to figure out where the source of the problem is. We can only guess from here.
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dels56
Posted 2020-08-08 5:10 PM (#601804 - in reply to #600733)
Subject: Re: Spongy Brakes


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Yahoo...finally, got some brakes. After 2 NEW master cylinders! #1 Dorman, #2 Raybestos. Both with bad seals. Overhaul kit and very, very careful rebuild I’m winning. Front brakes only at this date. After getting most back together I had a leak at the adapter for the rear brakes. Ordered one, 9/16-20 but supplier sent me 9/16-18??. Local suppliers can not find the correct fitting so I ordered from Summit Racing, probably 10 days delivery. So on hold again until...
Del
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Stroller
Posted 2020-10-03 10:18 AM (#603931 - in reply to #600733)
Subject: Re: Spongy Brakes


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Late to the game here but what's the progress? Do the rear brakes gravity bleed? I once had a problem and nightmare to find. Turned out it was a cracked line fitting just inside the threaded section allowing air to bubble.
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dels56
Posted 2020-10-08 11:47 AM (#604188 - in reply to #600733)
Subject: Re: Spongy Brakes


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Update. As above, I finally have brakes but decided I am not done with them just yet. To answer the question, the front disc callipers Will gravity bleed. This is due to the design of the master cylinder having a path from the reservoir through the cylinder bore to the outlet port. The rears do not gravity bleed and with that you must pressure bleed. Either by having a bleeder valve open and pushing the peddle down and then closing the valve or pumping the peddle, hold it down and open the bleed valve. Naturally you would have a collection bottle attached either way.

What I will do next when I have time and energy, I will take the drums and shoes to a shop that has a grinder to fit the shoes to the drums. Then back to installing, adjusting and setting the clearance with the dial indicator. I am sure the shoes that are manufactured across the water do not end up perpendicular to the drum or if they are even the same thickness over the length of the lining.

Del S
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Powerflite
Posted 2020-10-08 2:00 PM (#604195 - in reply to #600733)
Subject: Re: Spongy Brakes



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If it's the rear brakes, I wouldn't bother with grinding the shoes. They aren't as sensitive as the fronts and you can get away with just letting normal wear bring them into spec. At least that's what I do.
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