Brakes... Pedal feel

[Ajgkirkwood]

Hi there. On my 1940 chrysler it still has the 11" drum brakes. They feel good and stop the car well but my issue is the pedal. If i dont pump the pedal first, when i apply rhe brakes and im down near the floor. It stops good but feep i wont have much more travel if something jumps in front of me. The master cylinder is floor mounted (at the pedal) would tying in a brake residual valve help this? With 4 drums to the master cylinder would a 10 psi work or do i need higher? I want the pedal to start feeling pressure when i start to apply the brakes not like 1/2 - 3/4 way down.

 

[Plymouthy Adams]

your stock configured master cylinder with factory drum brakes already has a residual valve.   If low pedal and good brakes could be time to adjust the shoes closer to the drum surface.  If low and spongy..would say air in line...  I suggest adjusting the brakes...read your manual for the procedure...it is a step by step process.  The correct tool is truly a must for proper adjustment to ensure even wear of the shoes.  Study your brake section of the manual before proceeding..

[MackTheFinger]

My '47 did that last weekend,, turned out to be a leaky wheel cylinder. Not bad enough you could see it without pulling the drum.. 

[soth122003]

I am going thru this problem right now. I adjusted all the brake shoes, checked for leaks and I found a leaky corroded wheel cylinder and fixed it but still have the problem. I am thinking that I have a problem with   the Master Cylinder causing the brake pedal to be low.. My current theory is the brake fluid is about 4-5 years old and has a little water mixed in now and that has caused crud to form in the MC bore and is causing one of the cups not to seal well. So when I press the pedal it is firm at about 2 inches from the floor, but you can pump it one to two more times and the pedal is firm at about 1-2 inches of travel. I am fixing to pull the MC and check and will update later today.

Edited April 12, 2018 by soth122003

[Don Coatney]

If you must pump the pedal to get it to the top you have air in the system. Time to bleed the brakes.

[Adam H P15 D30]

7 hours ago, Plymouthy Adams said:

your stock configured master cylinder with factory drum brakes already has a residual valve.   If low pedal and good brakes could be time to adjust the shoes closer to the drum surface.  If low and spongy..would say air in line...  I suggest adjusting the brakes...read your manual for the procedure...it is a step by step process.  The correct tool is truly a must for proper adjustment to ensure even wear of the shoes.  Study your brake section of the manual before proceeding..

The key words are in bold.  These brakes are really good right up until they're not.  Without the tool they will only be close but never right.

 

Edited April 12, 2018 by Adam H P15 D30

[knuckleharley]

8 hours ago, Ajgkirkwood said:

Hi there. On my 1940 chrysler it still has the 11" drum brakes. They feel good and stop the car well but my issue is the pedal. If i dont pump the pedal first, when i apply rhe brakes and im down near the floor. It stops good but feep i wont have much more travel if something jumps in front of me. The master cylinder is floor mounted (at the pedal) would tying in a brake residual valve help this? With 4 drums to the master cylinder would a 10 psi work or do i need higher? I want the pedal to start feeling pressure when i start to apply the brakes not like 1/2 - 3/4 way down.

 

Adjust your brake shoes and flush,refill,and bleed your master cylinder.

[soth122003]

Well it was the left rear wheel cylinder. I cleaned it and honed the cylinder yesterday and when I checked this morning I had a puddle of fluid under the left rear tire. Good thing I didn't return the drum puller. Pulled it apart and it was dripping good. Didn't drip till I pulled it and attempted to repair. Pulled it today honed it again and used a cylinder kit for repair, an hour later it was dripping again. I guess the corrosion was to much. New wheel cylinder will be here tomorrow. Since I am waiting for the wheel cylinder I thought I would check the MC. Disconnected the rear brake line and plugged the MC and BAM, the pedal was rock hard at 1 1/2 inches of travel.

 

The thing that weirded me out about this was the pedal wasn't spongy, just low. With the one pump to bring the pedal up it felt like an adjustment issue. I guess with the corrosion issue it would not let the wheel cylinder work right even though it wasn't leaking bad (the drum area was moist). Once I get the new wheel cylinder, I'll flush and bleed the system.

[knuckleharley]

9 minutes ago, soth122003 said:

Well it was the left rear wheel cylinder. I cleaned it and honed the cylinder yesterday and when I checked this morning I had a puddle of fluid under the left rear tire. Good thing I didn't return the drum puller. Pulled it apart and it was dripping good. Didn't drip till I pulled it and attempted to repair. Pulled it today honed it again and used a cylinder kit for repair, an hour later it was dripping again. I guess the corrosion was to much. New wheel cylinder will be here tomorrow. Since I am waiting for the wheel cylinder I thought I would check the MC. Disconnected the rear brake line and plugged the MC and BAM, the pedal was rock hard at 1 1/2 inches of travel.

 

The thing that weirded me out about this was the pedal wasn't spongy, just low. With the one pump to bring the pedal up it felt like an adjustment issue. I guess with the corrosion issue it would not let the wheel cylinder work right even though it wasn't leaking bad (the drum area was moist). Once I get the new wheel cylinder, I'll flush and bleed the system.

You have a single outlet master cylinder. Chances are your other 3 wheel cylinders and your master cylinder are as old as the wheel cylinder that has already gone bad.

 

Do yourself a favor and buy 3 new wheel cylinders (cheaper to buy new than rebuild),and a new master cylinder. If it were me,I would also replace the brake lines and hoses.  Look around and see what a replacement grille alone costs for your car,and then compare that to the price of a total brake rebuild. And that is assuming the grille would be all you would trash.

[soth122003]

Hey Knuckleharley,

I already replace the lines and hoses a few years ago. At the same time I rebuilt and honed all the wheel cylinders and the MC. Just that that particular wheel cylinder was the worst of the lot. It had some pitting issues I could not get out. The cylinder now has a small gouge about .0005 deep  from the piston in that cylinder. I also heard most of the new wheel cylinders made today are crap and won't last but a few years, so I will have the old ones bored and re-sleeved in brass. Being I am on a very limited budget for the next few months/years, and it is six wheel cylinders (2 for each front) I'll buy the one I need now and re-sleeve that one then do the same for the other one in a few months. When I have a front one leaking I'll do the same thing again. Sorta spreading the lump sum payment out so to speak.

 

Gotta do this for now as Momma's car is in the shop awaiting a new engine due to a wrist pin going bad at 71000 mile and the engine is on back order for the next few weeks, making my car the primary until hers is fixed. Gotta love that 100000 mile and 10 year warranty.

 

Oh and FYI, I already have a grill plus complete set of front end trim as well as the wing windows, beauty rings, hub caps and some assorted trim pieces for the car should I need them. Came with the car when I bought it.

 

Joe Lee

Edited April 13, 2018 by soth122003

[keithb7]

I went through my brakes in Feb in preparation for the up coming cruising season. Compared to what they were, they feel geat overall. Stop well. No pulling. No noise. Reading through the comments here I would be inclined to say that, ya I notice the first pump of the pedal after sitting some time, has more travel. After 1 pump  everything feels like new. Little travel and great feel.  To summarize I completed the following:

 

Master cylinder hone and rebuild. All new flex lines. 2 new rear wheel cylinders. Front 4 wheel cylinders rebuilt. New brakes line from master cylinder to junction block. All new rear brake lines from junction block. . Shoes reused as they were about 50% worn. New bleeder screws. All linkage cleaned, inspected lubed. All new brake fluid.  Brakes bled extensively. Brakes set up as best as possible without the $500 tool. After 100 miles all drums removed again to inspect for any leaks. None found. Bled again with helper on the pedal, me at each wheel. I get under the car about weekly with a good light to inspect. No moist connections. No drips. Nothing concerning. 

 

Symptom still persists. Its not bad but I do notice it. After that first pump of the MC the brakes are all I’d hoped they’d be. Hmm. I can live with it just fine but I would like to get to the bottom of it.