1938 buick brake problem

[Guest 38 special]

Hello every one my name is Joe and im a newbie here id like to thank you in advance for any assistance i have a 1938 buick special totaly restored my first time taking her on a spin and after abought 20 min on the road my brake pedal gets rock hard so i take her back to the garage readjust rebleed brakes and the same thing happens im thinking maybe a bad mastercylinder i have all new brakelines new wheel cylinders i just cant figure it out any help is very much appreciated,:mad:

[ply33]

On hydraulic brakes, at least those of that era and maybe even today, having the brakes lock up and the pedal getting rock hard is a symptom of the relief port in the master cylinder not being open. And a classic reason for that, aside from dirt, is having the push rod from the brake pedal to the master cylinder adjusted too long and not allowing the piston in the cylinder to fully retract. (Or, in the case of a recent thread, having the master cylinder assembled wrong with a cupped washer keeping the piston from fully retracting.)

You don't say that you've worked on the master cylinder, so maybe its dirt that is clogging the relief port. But if you've worked on it, especially if the connection between the pedal and the cylinder has been adjusted to get a better pedal height, then you should review the work done.

[Guest 38 special]

Thanks i have rebuilt the master twice im thinking thee adjustment from the master to the brake pedal i will check in to it thank you for your advise

[Marty Roth]

When you look at the master cylinder, check to assure that there is free-play in the push-rod.

The "ball" end of the push rod which goes into the master cylinder should have the ball between the domed-washer, called the "stop-plate" and the piston. The dome should be outward, allowing the expanded mushroom or ball shape of the rod to be between the piston and the plate.

Mine was assembled backward by someone, and we have fought the same problem with much great advice from the good folks on this forum, until I inadvertantly noticed that the stop plate (or end washer) was backward, and that the rod had to push against the washer as well as the piston, and that the piston was not allowed to fully return, and that was building pressure in the brake system. Every so many miles, I had to stoip and crack a bleed screw, or the brake lights came on, the brakes applied, and the drums got really hot. Since reassembly, I drove the car 185 miles one day a week ago with no noticeable problem.

Good luck, and you can look at my posts under Buick General Discussion, as well as the main General Discussion.

http://forums.aaca.org/f115/brake-problem-pedal-gets-hard-tight-314998.html

http://forums.aaca.org/f169/brake-problem-pedal-gets-harder-tighter-314997-4.html#post973946

Edited December 28, 2011 by Marty Roth
add reference sites (see edit history)

[Guest 38 special]

Marty i read your thread and it was an exact replica of my problem i have been on this for abought 3 months my wife thought i was going crazy id take the car out for a spin brake light would stay on brake pedal would start to get hard back to the garage for a brake tear down go thru the system open the master resized the ports on master

and try again my final stop here before i send off to a brake shop,so tonite my wife said pray on it and im sure you will find the anser a men to that my prayer has just been anserd just by reading your thread my problem has been solved . thanks a million Marty,

Edited December 28, 2011 by 38 special (see edit history)

[38Buick 80C]

In the two threads about Marty's brake issues some have noted the brake hose out of the master cylinder or the the hose from the chassis to the torque tube as the issue. This is a common problem where the hose looks fine but is not and swells internally and will not allow the fluid to return from the wheel cylinders. If they have not been replaced with new ones I highly recommend it even though it sounds like you are experiencing something different than this issue.

Good Luck. Where are you located?

[trp3141592]

Hi,

There is a recent (within the last 2 weeks) thread regarding brake hoses on a newly-acquired 46 Buick (thread is titled, "1946, Buick, just purchased?") over in the Post War forum. Lots of information there regarding hoses, including my 2 cents worth.

--Tom

[Guest OLBUICKS]

No one has mentioned that there is a grease fitting under the car at the MC that may need some new grease. It's where the clutch and brake pedal pivots on a shaft under the car.. Just a thought..

[Guest 38 special]

Well i tore down the master cylinder everything was in its proper place the stop plate was in properly installed another rebuilt kit on master drove it around for a bought 40 min brake pedal got hard again. some one mention hoses colapseing i have all new hard lines and rubber lines un less any of them are faulty,Idid notice that when the pedal got hard again, i jacked up the rear end and cracked the line the brake fluid was hot not boiling hot but it was abought as hot as a cup of coffee ,so i checked the master that baby was hot abought as hot as a iron i coudnt keep my hand on it im wondering if i need to reroute the muffler any one have any ideas thanks alot guys for all your responces, Joe in los angeles california

[Guest 38 special]

No one has mentioned that there is a grease fitting under the car at the MC that may need some new grease. It's where the clutch and brake pedal pivots on a shaft under the car.. Just a thought..

ill check that thanks

[Guest 38 special]

In the two threads about Marty's brake issues some have noted the brake hose out of the master cylinder or the the hose from the chassis to the torque tube as the issue. This is a common problem where the hose looks fine but is not and swells internally and will not allow the fluid to return from the wheel cylinders. If they have not been replaced with new ones I highly recommend it even though it sounds like you are experiencing something different than this issue.

Good Luck. Where are you located?

all brake lines are new rubber and hard unless there fualty? im in los angeles

[Marty Roth]

Remove the fill cap and look down inside the master cylinder. Make sure that when the piston retracts, it goes all the way, and that fluid pushes up through BOTH holes, the primary, and the relief passage.

Are you sure that the mushroom end or the rod is between the inside of the stop-plate and the dished end of the piston? -- and that it has a minimum amount of free play?

Be sure that there is some free play in the rod as it enters the cylinder, and that the pedal returns fully.

Others have discussed heat, but I believe that heat from the exhaust system, or the engine will cause the brake fluid to foam, and to cause a spongy pedal, not a hard pedal. This was confirmed by several other well-respected restoration specialists.

You might try what I did as a TEMPORARY TEST, that of removing the check valve in the far end of the M/C. That proved to me that my problem was really IN the M/C.

Let us know each step along the way - there is a lot of real talent out here - they got me through it !

PS: I believe that your heated braske fluid is a result of the brakes being self-applied - the brake drums get real hot - the fluid overheats too!

Take along your laser temperature gun - I bought a cheap one from Harbor Freight - When you drive and the brake light comes on, check the temperature of all four brake drums and all four wheels. If all are hot, then your problem is in the M/C or the hose right behind it. If only the rears, or only the fronts, or only one wheel, then there is the problem at that location.

Good luck!

Edited December 29, 2011 by Marty Roth (see edit history)

[Terry Stock]

I'm no mechanic but know just enough to hope, Joe, that the restoration included new brake pipes.

We had a brake problem a couple or so years ago. Car was about to be road tested after other brake work and the original (about 70 years) pipe burst. OK in the workshop, but it would not have been much fun on our hillside road.

Those pipes can corrode from the inside so get them replaced with modern materials if you haven't already.

[trp3141592]

Hi,

Bottom line with your problem is that brake fluid is being prevented from returning to the master cylinder. That can happen in only three places: Wheel cylinder, brake lines, and master cylinder.

Consider:

1. Wheel cylinder is not retracting when the pedal is let up. Inadequate shoe return springs would not account for the pedal lock-up. All four cylinders would have to be jammed or gunked up to deny return prssure to the fluid. This is not likely since you have had the cylinders apart.

2. Brake lines: This is still my #1 suspect. Deteriorated, defective, or collapsed rubber hoses can look good, but, if collapsed inside, they can prevent fluid return. Did you buy DOT-compliant hoses, or the $20.00 crap from Argentina that is listed on EBay? Been there.

3. a.) Master cylinder assembled incorrectly--check valve backwards? Master cylinder adjusted incorrectly, denying relief of fluid. c) Crud-blocked relief hole in reservoir of MC. d) Incorrect piston in Master Cylinder--after reading this thread I am now leaning toward this one. Wrong rebuild kit? Wrong piston? I don't have access to Buick part numbers to check, but I am guessing different models had different master cylinders due to the different weight of various models of the cars. Call Bob's Automobilia for help determining what is correct for your car.

Take heart! The hydraulic system is really pretty simple technology--there certainly is a determinable cause to your problem, and you WILL chase it down.

--Tom

Edited December 29, 2011 by trp3141592 (see edit history)

[Guest 38 special]

Im going to trouble shoot the next couple of days I just wonder is it normal for the master cylinder to be so hot,i can understand the fluid getting warm running thru the brake lines but this master gets pretty hot and im starting to think that could be my poroblem i can pump the brakes while the car is cold and they work fine but but when i start the car and pump after the car warms up u feel the presure building and im not even driving it, its just idleing is it common for the master to be hot for this particular year this is my first buick restoration so i am in unfamiliar territory thanks again fellas i really apreciate your input ,Marty its is all 4 wheels that are locking when i took apart the mc the push rod was in side backing plate the ball on the push rod sits in side of the piston the hump end of the backing plate faces the push rod allowing the piston to come out more push rod has freeplay in it does that make sense any way im off the garage to see what i can figure out ill keep u posted thanks

[Marty Roth]

From your description, it seems that the pushrod side of the M/C is properly assembled.

With the brake not engaged, the piston must be back against its stop with 1/8 inch clearance between pedal rod and both ports must be open.

As depressed pedal is released, the main spring forces piston back faster than fluid returns from wheel cylinders and reserve fluid is drawn through piston vent holes past the primary cup. When line pressure drops to 7 to 12 pounds, the check valve closes.

When the cap is opened, and you depress and then allow the pedal to return, can you see fluid squirting up from both passages? It should squirt up from the main and bypass passages which are correctly called the breather (larger) hole and the compensating (smaller) port. You may want to take a proper-sized drill bit and carefully make sure that both passages are completely clear. I have heard of a cylinder which was re-sleeved, and the sleeve was not drilled to allow for the bypass compensating port.

When you are sure of these both squirting fluid as the pedal returns, and you know that you dao have push rod free play, try my TEMPORARY suggestion of driving CAREFULLY without the check valve - if this seems like it is a lot better, then the problem is still in your Master Cylinder (wrong length piston? - Wagner Vs Delco? )

[Guest 38 special]

So no matter how hot the MC gets that would not make a diffrence,only reason why im asking is becuase the engine in my 1938 buick is out of a 1941 buick with a dual carb set up and the exhuast system is not the original set up i have a 2 inch pipe that runs abought 3inches from th mc and it gets pretty hot and i thought that was making the brake fluid exspand there for cuasing pressure build up today i put a heat sheild on it and the MC still got hot along with sheild, tomorrow ill check the rubber lines i put in. give u guys feed back tomorrow night thanks tom and marty.

Edited December 30, 2011 by 38 special (see edit history)

[Guest 38cadillacjack]

l am not sure if your buick is the same as my 38 lasalle,i think so,i was given the advice to replace master cyl. with one from a fork lift.i cant remember the #,but i do have it in the shop and can get it later.the new cyl was a direct bolt in and works perfect .cost was 35.00 on ebay.easiest way to cure the problem.looks exact also.good luck

[FLYER15015]

I just love it when the story "dribbles out".

After everybody offers up their ideas, we find out the exhaust pipe is 3" from the MC.

DUH?

1. Reroute the pipe

2. Wrap the pipe w/ insulation

3. Wrap the MC w/ insulation

4. Put a cooling fan on the MC

Mike

[danhar1960]

4. Put a cooling fan on the MC

Mike

A fan cooled Master cylinder, now there's a new and interesting idea. :)

The beauty of right hand drive is the master cylinder is on the opposite side to the exhaust system.

Danny

[trp3141592]

Hi,

Is it then the current theory that the heat expands the aluminum piston more than it expands the cast iron MC and makes it jam in the MC?

--Tom

[FLYER15015]

TRP,

That could very well be true, but after the latest revelation (ex 3" fr MC) I have a hunch that the heat from the pipe heats up the whole friggen unit and expands the fluid to the point that the brakes slowly "come on".

I forgot solution #5. Which is to take Danny's idea and convert the car to RH drive.

Mike

[Marty Roth]

My Exhaust is also only 3 inches from the Master Cylinder, but now not causing a problem.

I don't think that the heat is necessarily the problem.

I think that the heat is probably coming from driving the car with the brakes applied as a result of pressure in the system not being released.

Let's not jump to a possibly false conclusion - the original exhaust was on that side as well, and just because he has dual carburetion does not mean extreme exhaust temperature.

ALSO - when brake fluid gets hot it will foam, and that would cause a "spongy" pedal.

[Guest 38 special]

I checked MC today with a lazer gun at its hot is point 160 the reason i never mention the pipe being 3 inches from MC is becuase a well known buick machenic out here in L,A told me that no matter how, hot the mc got that would not cuase the brake system to lock up, and if the rubber hoses wher fualty that would only cuase one side to lock or just the back not all 4 wheels right ?so i got the car up on jackstands i am going thru the whole frekin system again i dropped all four tires took off all the drums i will continue tommorow, im wondering if the block i dont know its proper name where all the lines connect and the brake light switch connects too the jucntion block could be clogged or fualty like i mention in a earlier post i did put a heat sheild on it but that did not work,i will give you all my findings tomorrow thanks guys for all your help, Oh and flyer already had a right hand drive i felt like the mail man ill pass on that idea buddy lol

Edited December 31, 2011 by 38 special (see edit history)

[Marty Roth]

My 1937 Roadmaster has an additional rubber hose right behind the Master Cylinder, going to the junction which splits fluid to one line going to the rear axle, and two others , each going to a front brake. This hose could be separating internally and acting as a check valve --- I still think your problem is in the Master Cylinder.

Are you getting fluid squirting back through both passages when the brake pedal returns?

[Guest 38 special]

Marty i think that the piston in the master might be to long? im tearing it all down oh the rubber lines are all new all 3 of them they might be fualty ill check in to it,al so i was just in formed that buick in 1938 came out with a spring like a retainer spring that would cuase all kinds of problems i was told to remove those they some times keep shoes from closing all the way keeping air in the lines it was a one year only and they discontined them in 1939 anyway ill fill you in tonite im off to tackle this,Just got a call from my buddy BoB who restores buicks he said that my master is in good shape he rebuilt it for me this last time he told me to remove those retainer springs

Edited December 31, 2011 by 38 special (see edit history)

[trp3141592]

My 1937 Roadmaster has an additional rubber hose right behind the Master Cylinder, going to the junction which splits fluid to one line going to the rear axle, and two others , each going to a front brake. This hose could be separating internally and acting as a check valve ---

I didn't recall a hose being located immediately behind the master cylinder. If this represents a 4th rubber hose in the system, it may have been overlooked for replacement. Bob's Automobilia lists it for $48.00 at:

Brakes

And I am going out to the warehouse right now to see if I replaced this hose on the 37 Roadmonster when I did the 100% (or so I thought) brake job a few years ago!! :-)

--Tom

[Marty Roth]

Hey 38 Special,

Any word yet on your progress?

We hope you have identified the problem, and have made the fix.

Let us know the results - we all run into these things sometimes.

[FLYER15015]

38 special,

Been watching this thread for two weeks, and no more info.

Did you solve the brake problem ?

Care to share the solution, with all those who offered up their ideas ?

It will help a "newbe" later when they do a "brake problem" search.........

Mike in Colorado