1938 66C brake problem

[Guest Gene P]

Awhile back I posted a question regarding the brakes on my Century. After a complete brake system rebuild, the pedal went almost to the floor before I got a "hard" pedal. I received several suggestions, which I have followed through on. There is no air in the system, I have adjusted the pedal to floorboard clearance, and gone through the eccentric adjustment. I still have the same problem; when depressed, the pedal goes to within one and 1/2 inches to the floor. At that point, the pedal is solid and the car stops. There does not seem to be any resistance until I get to that point. I know I'm missing something but I'm at wits end. Any suggestions?

[1939_Buick]

http://forums.aaca.org/f165/1938-century-brake-problem-345427.html

My 1938 Century came out of 40 years of storage needing, among other things, a complete brake O/H. Everything was replaced except the steel lines....

Are the steel lines clean & clear ? Did you clean / flush the lines. Or 40 years on old solid oil in them ?

With the wheels off the ground does brake stop each wheel evenly ? Can you feel when the pads are are working on the drum ?

(we like photos)

Edited April 29, 2013 by 1939_buick (see edit history)

[Barney Eaton]

There is a chance your master cylinder is assembled wrong or has incorrect parts. When the pedal is up, the holes in the bottom of the resevoir must not be covered/blocked with the piston cups. While that is a very basic master cylinder, someone could have messed it up.

[Guest Grant Magrath]

Have you adjusted the shoes? Pedal comes up heaps when the brake linings are adjusted up correctly. But if you've done that. and still no joy, make sure the linings are making good even contact with the drums. Sometimes only part of the linings touch the drums, and excessive pressure on the pedal is needed to stop the car.

Cheers

Grant

[danhar1960]

This is just an out there question but are you totally sure that the wheel cylinders are the correct size ??

Bigger diameter cylinders than the correct ones will give an excessive pedal travel. The fronts are bigger than the rears.

(Unfortunately, the only way to confirm that is to remove and measure.)

I did run across a car years ago with front sized cylinders on the rear. (Wasn't a Buick though)

Did you try adjusting all 4 wheels to the max (totally locked up so that the wheels just wont turn) and see what the pedal does ??

At least that would eliminate shoe adjustment as the problem.

Danny

[Guest Gene P]

You guys have given me a wealth of checks to perform. I did flush the lines multiple times with "brake cleaner" and air; appeared to blow clean. The wheel cylinders were all good; I cleaned them, and reassembled with new cups. (That's not to say I couldn't have switched front to rear although I don't think so.) Today I'll adjust them all to "locked" and check the pedal. I purchased a rebuilt sleeved master cylinder and installed it using Dot 5 brake fluid. I pulled the front drums last week to replace all the bearings and contact with the shoes appeared uniform. I'll follow up with the other sugestions and get back.

[Steve_bigD]

The brake shoes are centered vertically by the anchor pin adjustment and the secondary (rear) show is adjusted via an eccentric so that there is .010" clearance at each end of the shoe about 1.5" from the ends. The anchor pin adjusts the end clearance so it is equal (.010") top and bottom, while the eccentric adjusts the shoe horizontally to get the clearance at the ends. Due to the arc of the shoe linings when the clearance is set to .010" the center of the shoe is rubbing slightly on the drum. Thus the star wheel actually only adjusts the primary shoe clearance with the drum.

The procedure is to set the anchor pin first by tightening the star wheel so the drum can barely be turned by hand, loosening the anchor pin nut and tapping the nut with a mallet so it assumes the correct centering. Then tighten the nut. Next the eccentric is adjusted for the secondary shoe end clearance as indicated. Therefore the star wheel must be backed off so the drum turns freely with the eccentric loose so the secondary show can be adjusted without interference from the primary shoe. Lastly after the eccentric is tightened the star wheel is adjusted for proper primary shoe clearance.

If the eccentric is not adjusted for the proper end clearance before the star wheel is adjusted the no amount of star wheel adjusting will give proper brake feel and the peddle could be low. Also don't mistake the slight drag from the secondary shoe curvature for proper adjustment when adjusting the star wheel otherwise you may think the star wheel is adjusted correctly when in fact due to the secondary shoe drag there is a lot of clearance and again a low pedal.

Steve D

[Guest Gene P]

Since the car is on jack stands, I went to a quick test as suggested. I adjusted all starwheels to the point that I couldn't turn any wheel by hand. And, the pedal still went to the floor! I think I just eliminated adjustment as my problem. When I look into the master cylinder while pushing the pedal down, I can see the seal in the rear port as I believe is correct when released. The front is open to the piston area. With pedal down, I can see the seal in the front port. When I first installed the new master cylinder and tried to bleed the brakes, no pressure came from the master cylinder. I contacted the supplier and was told that I had to maintain pressure on the master cylinder outlet in order to bleed the master cylinder. Although I've never had to this before on any number of cars I've worked on, I did as directed and it appeared to have solved the problem, I had pressure to the wheel cylinders and bleed the lines, several times. But, the hard pedal only comes as it approaches the floorboard. Does this better define where the problem may be?

[Guest Grant Magrath]

Steve D's procedure would be the one I'd be doing if I were you Gene.

Cheers

Grant

[danhar1960]

Most curious !!

Sounds like it's back to the master cylinder.

I remember a thread a while ago where somebody had a similar problem.

If I recall rightly, he ultimately found the the retaining ring at the end of the master that retains the adjusting rod (and holds the piston into the cylinder) was around the wrong way. It had a curved recess that the rod sits into and being around the wrong way prevented the piston from returning to its proper home point.

Just a thought. Running out of ideas.

These things are always a stinker when you can't physically be at the car.

Danny

[Marty Roth]

Danny, you have a great memory....thanks for thinking of us, but No...Different Problem...!!

In my 1937 80C Master Cylinder the retaining ring was wrong-way around, but it caused the piston not to return completely, and to build pressure in the system to the point of the brakes locking up as you drove. We have since driven thousands of trouble-free miles thanks to the great advice received on this forum, and having noticed the backward ring, apparently assembled that way by whomever "overhauled" the brake system before I bought the Roadmaster Phaeton.

[Guest Gene P]

Sounds like there is still some feeling that the problem could be in the shoe adjustments. I had about come to the conclusion that it was a master cylinder problem after I adjusted all wheels to "locked" with no effect on how far the pedal goes down.

[Guest Grant Magrath]

Probably a 38 problem. I was never happy with our 38 Special pedal. And that was a lining issue.

Cheers

Grant

[danhar1960]

You're right Marty, it's all coming back to me now. It was as you say, a different set of symptoms.

This is indeed odd. They don't come much more basic than these braking systems.

In your original post you said everything was replaced.

Was the master replaced completely or just replaced the seals ??

Did you or someone else do the work ??

Did you replace the linings as well as the hydraulics ??

Were the drums machined ??

These brakes usually come up well although correct adjustment is critical.

2 of the '39s I had have had the eccentric cams and the others didn't. I eventually went with no cams as they were ultimately dispensed with so I figured it was more '39y.

Those with were very early production so I assume they just ran out the old stock backing plates.

Curiouser and curiouser.

Danny

[DonMicheletti]

Grant,

I have to disagree with you. I have 38's. Roadmaster and Special. Both brake systems work properly - and will stop the car. Something has to be wrong with this brake system.

Don

[Guest Grant Magrath]

Fair enough Don. Only had the one 38, so it was a bit of a generalisation. And yes, something is wrong, as there was with our 38 as well. Just never bothered to fix it as it wasn't so much of a problem for me, and it was my daily driver.

Cheers

Grant

[Daves1940Buick56S]

I can only think of 2 things at this point:

1. There is still some air somewhere in the system

2. Master cylinder problems

Cheers, Dave

[danhar1960]

If only we had Star Trek style transporters.

Sure would be handy on occasions such as this. :)

Danny.

[Guest Gene P]

I did replace linings that were NOS oversize and arced to fit drums. The wheel cylinders were simply cleaned with new cups installed. The master cylinder is a sleeved unit purchased from "Bob's". It was assembled when received and I did not disassemble. I bled the lines numerous times thinking there was still air in them due to the fact that the pedal wouldn't come up, although there was no "spongey" pedal, just went too far down prior to engagement and pumping the pedal has no effect. I'm at the point of pulling the MC and starting there although I'm not sure what I'm looking for. I think that's the only thing left to attack.

[danhar1960]

Gene,

Radially ground linings to fit the drums will eventually pay dividends.

I'm inclined to agree that M/C removal is the next step.

It's generally acceptable to believe that the new part will be correct but it defiantly isn't a absolute. Marty's M/C was a good case in point.

At the risk of being a bit repetitive, if those anchor pins aren't set just right (that is too low) it will defiantly stop you from getting a full pedal.

If you do pull the M/C, take some pics to post. Maybe someone will be able to spot problem.

Danny

[Guest Gene P]

I hate to show my ignorance, or age, with my lack of "computer litteracy", but I haven't figured out how to post pictures yet!

Gene

[Pete O]

Just spitballing here- is it even possible to install the pistons in the wheel cylinders the wrong way? The flat sides should face inward toward the cups and spring, and the dished side should face outward. If the pistons were reversed (is this even possible?) the internal volume of the wheel cylinder would be greater, requiring more brake fluid to make the pistons expand. Again, like I said, just grasping at straws....

[critterpainter]

quick check to isolate the problem. Put a vice grip on the flex line coming out of the master cyl and then step on the brake pedal. Now does the pedal go to the floor?

If not then use the vice grip trick on the other flex lines.

Bill

[Guest Gene P]

That is a great suggestion! I hadn't thought of that. If the pedal still goes down, the problem is isolated to the master cylinder. Other wise, I should be able to isolate where in the system the fault is. I will be able to perform check tomorrow and will report the result.

Thanks, Gene

[jenz38]

I think too,the ptoblem is the "new"MC,its wrong assembled . Sorry to say that but we here never trust in new or rebuild Parts from the States (Mexico,Taiwan,..)without a disassemling an check all. Im not wondering with our Problem.

M2C

[Guest Gene P]

quick check to isolate the problem. Put a vice grip on the flex line coming out of the master cyl and then step on the brake pedal. Now does the pedal go to the floor?

If not then use the vice grip trick on the other flex lines.

Bill

WALAH! With the M/C hose clamped, the pedal would not depress. So, I went to the rear brake hose, applied the clamp with the same result; pedal would not depress. Keeping in mind that all wheels are adjusted to "locked", I assume I have isolated the problem to the rear axle. Tear down time. At least I have an isolated area to concentrate on. Will report what develops.

Thanks again for all the support,

Gene

[danhar1960]

Good to hear of a little positive progress. Maybe those rear lingings aren't quite centered right.

Danny

[Guest Gene P]

Well, I'm back to square one. My last post I thought I had isolated the problem to the rear axle. So, I proceeded to tear down both rear brake assemblies. I couldn't find anything obviously wrong; one e-brake cable appeared to be slightly binding so I freed it up and lubed it. I reassembled both assemblies and proceeded to go through the "centering" excercise, although viewing the shoes through the drum opening, there was very little variation top to bottom, primary and secondary.

In the process, I noticed a brake line that had a depression in it. I don't believe enough to cause a restriction, but since I was there, I decided to replace it. Job completed! Time to bleed the lines and see what I had.

I have a hand operated vacuum pump that I've used in the past and since I was alone, it made sense to get it out. I pumped that thing until my hands hurt with no results. So, I called a friend, they're getting where they don't answer the phone when I call, and got him down to pump the pedal. NOTHING! I checked the M/C, it was full, so I applied the clamp to the hose from the M/C again and guess what; the pedal went to the floor.

I may have more than one problem, but one thing's for sure, the M/C isn't doing the job. Now I'm back to attacking it.

A number of you stuck on the M/C as the most likely problem and it appears that you have been on target from the start. I believe that if I hadn't opened the system in replacing the line and had to start the bleeding process, I would have had the same problem after I finished. It's acting the same as it did on the initial fill. I think I mentioned that the supplier told me I had to keep "pressure" on the outlet to get it started. I never understood that, however, when I clamped the hose, that should have had the same effect.

Back to the drawing board tomorrow.

Gene

[jeff]

From your experiment with the vice grips...

I may be mis-reading it, but isn't your logic backwards? When you clamp off the m/c line, you are taking all of the wheel brakes out of the equation - the pedal should not move, and it didn't. When you clamp the rear line, you are taking the rears wheels (and their compliance)out of the equation. Now, you should get some pedal travel, since the m/c is only working against the front compliance. If the pedal felt the same (essentially no travel) from your first experiment to your second, I would suggest an issue with the fronts. (as I said, I may have mis-read your postings)

Now, to your inability to get a reasonable bleed after opening up the system, you may have another issue with the m/c. Check your vented m/c cap to be sure the cross drill is open. A friend experienced the following - some fluid would come out on the first attempt to crack a bleeder screw, but then each subsequent attempt gave us a low pedal, and very little additional fluid would come out. The reason was the vent was blocked, and the m/c would not re-fill after a bleeder screw was cracked. I won't tell you how long we fought with this, until the venting idea occurred to us!

On my '38, I had to search for the cross drill - it was completely closed off with grime and rust, then painted over.

Good luck,

Jeff

[Guest Gene P]

I may have been "confusing" in my description of the tests. Initially, when I clamped off the M/C hose, the pedal would not go down at all. That indicated to me that the M/C was being pressurized and the problem had to be beyond the clamp, ultimately at the rear axel. After opening the system, I applied the clamp again on the M/C hose and the pedal when to the floor, no pressure from the M/C. I will pursue your suggestion on the vented cap. It would nice if that was effecting the system as it would be a simply fix.

Thanks again, Gene

[danhar1960]

Gene,

It may be that you have a dodgy/defective cup in the M/C that only works intermittently.

My old daily driver Hyundai has a clutch pedal that will occasionally just drop to the floor. I take my foot off, push the pedal again and I have full pedal. It started doing this years ago and it would happen about once every 3-4 months but now it happens once a week. I know it has to come out, I will get to it.

If you do pull the master, have a real good look at the cups for deformities or irregularities in its form. It may be worth just changing the 2 cups just to eliminate them.

Also have a good look down the bore for any signs of problems.

If you can take some pics, email them to me and I'll post them for you. What you may not see may be obvious to someone else.

Danny

[Guest Gene P]

Well, perhaps I have had some sucess finally. I removed the M/C and disassembled it. Everything looked fine although there appeared to be some "black" residue, probably rubber "filings" in the bore. There's not much to inspect other than the relief valve at the outlet. I could pull some air out of it but I was unable go the other way. I purchased a new kit at the local parts house and applied the same test on the check valve, and found that I was able to move air in both directions easily. I reassembled it but had to use the old piston as the new one would not go in the resleeved cylinder; maybe .003 larger. With the new main cup and new spring w/valve I am now able to draw fluid out of the M/C by vacuum, and I have mouth full of Dot 5 to prove it. I have lots of reassembly to do now, complete bleed of the system, and some final adjustments before I'll know if the problem is solved, but I have high hopes.

I'll keep you all posted and thanks again for all the help; great place to be when you're in trouble!

Gene

[Guest Gene P]

One correction to my previous comments; when the supplier was contacted, they acknowledged that they do not ship the M/C assembled. I obviously assembled it although I don't remember the details. My memory is worthless beyond 30 days, if I'm even good for that. At any rate, I don't think I would have questioned the operation of the check valve, if that does ultimately turn out to be the problem.

Gene

[Guest Grant Magrath]

Good luck Gene!

Cheers

Grant

[Guest Gene P]

Well, success at last! I got everything reassembled today and got help on bleeding the lines. The vacuum pump just won't do the job. I now have a good hard pedal at a reasonable point in the travel. I need to do some final adjustment on the shoes and take it out for a test drive. What a journey this has been! And, the problem was in the least likely place I could have ever imagined. Thanks to all the folks for giving me the encouragement to keep plugging away.

Gene

[danhar1960]

Gene,

Are you saying that the system just wasn't bled properly ??????

Danny

[Guest Gene P]

Not at all. The "check valve" in the M/C was not allowing the free flow of fluid. I don't know how I ever got the air out of the system initially. It must have been operating somewhat or partially.

Gene

[Guest Gene P]

Grant,

I have to disagree with you. I have 38's. Roadmaster and Special. Both brake systems work properly - and will stop the car. Something has to be wrong with this brake system.

Don

Right on target! After a few final adjustments, I went on the road and couldn't be more pleased. As good as any braking I've ever experienced short of power assist and not much short of that. Thinking back, I was foolish to have been driving it with the problem I had; they could possibly have failed at any time.

Thanks again for all the suggestions and support,

Gene