Brakes 37 LaSalle

[DLoucks]

Hi everyone, I am new to the club and own a 1937 La Salle  5019.  I am going through the brakes and I am unable to remove all the air from the system.  I replaced all wheel cylinders, hoses, springs and linings.  The prior owner told me he had replaced the master cylinder before my purchase in February.  Before I began the brake work, the pedal was firm. After completing the work, I bled the system, but the pedal still goes to the floor. Clearly there is still air in the system.  It's been decades since I replaced brakes on a car, and I must be missing something fundamental.  I suppose it is possible that the master cylinder could be bad.  Also in looking at the shop manual, it is suggested that the end of the bleed hose be in a jar with brake fluid, perhaps to avoid air from being sucked back in, not sure. 

Advice to a novice is appreciated.

Thanks,

Dennis Loucks

[LaSalle5019]

Dennis,
I replaced the entire brake system in my 1939 LaSalle last year and had no problem bleeding the system.  Here is the process I followed:

With all the brake drums on the car, I adjusted the star wheel adjustment out to get some contact between the drum and linings then backed off a few turns. Next, I filled the master cylinder with fluid and found a helper. Start with the right rear wheel cylinder and put a hose on the end of the bleeder that goes into a glass jar (so you can see the end of the hose/bubbles/etc.) that has some brake fluid in it.  Keep the end of the hose submerged. I would pump the pedal (which just went to the floor until the last wheel cylinder) a few times, hold to the floor and my helper would loosen the bleeder and lots of air would come out. Close the bleeder before lifting the pedal and repeat.  On this first one, after several repetitions, I stopped and refilled the master cylinder as I was filling all the lines and the wheel cylinder - you don't want to run out of fluid in the master in the middle of this so refill often, otherwise you have to start over. I again repeated the pedal pumping, hold and bleeder release until it was all fluid coming out of the submerged hose.  Next I moved to the left rear and repeated the process and refilled the master.  Then on to the right front, then to the left front.  After I was all done.  I went back to the right rear and started over to ensure no bubbles at each wheel cylinder (same order - farthest to closest).

It takes quite a bit of brake fluid to do this method and I just scrapped the stuff that I caught in the jar to avoid any chance of contaminants (you have to dump some out after bleeding each wheel corner).  Once done, I went around and adjust the star wheels to get the brake shoes adjusted correctly.  I usually force them into the drum and then back off until they no longer drag.  Afterwards, I drove the car to put some miles on and got all the shoes to wear in a bit then re-adjusted.

If you bled the entire system but never adjusted the brake shoes to the drums with the star wheel, I wouldn't be surprised if the pedal went to the floor before engaging so that may also be your issue.

Good luck,
Scott

[carlhungness]

       I utilized the normal method to bleed the disc brakes I installed on my motorcycle a couple of years back which clones the method Scott described and had horrible luck. I had air bubbles for a couple of hours.
Then I saw a YouTube video which did the operation backwards, working from the caliper back to the master cylinder. Thus I wonder if the same method might be used on a drum brake set up: Force fluid from the wheel cylinder back through the line to the MC, drain some from the MC, then go to the next wheel, etc. If one opened the bleed screw on the wheel cylinder, put a hose on it attached to a syringe and forced fluid back through the line the result might be pleasing. The syringe has more pressure than a pumping brake pedal as it is acting on only one cylinder it seems to me.

[harry s]

Another consideration would be to separately or bench bleed the master cylinder before doing the wheels. Also be sure you don't have any leaks that would cause sucking air into the system.     Harry

[Alan Harris CLC#1513]

Out of curiosity, when the pedal goes to the floor, does it come up some if you pump the brakes? Trapped air in the system should compress enough when pumped to give you some pedal.

[DaveZ]

I'm with Harry. Fill the master first. When you bleed do not push the pedal all the way down. I don't remember exactly what it does, I would have to go read it again, but if you do and there is no fluid at the front of the MC it will never build up pressure. If I can find where I read that, think it was in the 40 WSM, I will give more details.

[LaSalle5019]

When you bleed do not push the pedal all the way down. I don't remember exactly what it does, I would have to go read it again, but if you do and there is no fluid at the front of the MC it will never build up pressure. If I can find where I read that, think it was in the 40 WSM, I will give more details.

I forgot that detail.  Don't bottom out the master cylinder stroke as you will get some fluid past the piston as you uncover a port.  It shouldn't introduce air in the system but you'll get brake fluid leaking from the push rod side of the master cylinder.  I just stuck a piece of wood under the pedal (~1-1/2").  My new master cylinder had instructions on what the plunger travel limit was - I don't recall now.  Thanks Dave for bringing that up.

[DLoucks]

Thank you all for your comments.  The pedal still goes to the floor.  I removed the MC, and after research, bench tested the MC.  Removed air from MC, reinstalled and no pedal.  Bled R/R again, a little bit of air. No air noted on L/F or R/F.  Was careful not to bottom out pedal, placed a 2x on floor board as suggested.  Purchased a new MC from Napa M4360.  Outside appeared same, but it came with a rod attached.  The original had a 1 3/4"x 3/8" (approx) length  in the piston to allow the pushrod to enter. The 4360, wasn't going to work, without modifying the brake rod that enters the MC piston. As far as the lines are considered, I haven't noticed any fluid on the garage food or other leaks that would allow brake fluid to escape.  At this point I will check with a Cadillac parts vendor to see if I can obtain the correct MC.  Other than that, I'm out of ideas.