1959 Cadillac Brake Question.

[ericdev]

I just had the brake system completely overhauled in a 1959 Coupe deVille with drum brakes at all corners. When cold, the brakes stop perfectly. But after driving a while, the pedal became very stiff with almost no travel and the brakes will be dragging. This is especially noticeable in reverse when the car really doesn't want to move.

 

On further investigation, it turns out the car need not even be driven for this to occur. Just becoming hot under the hood with the engine running results in the symptoms above. Once everything cools off under the hood, brake operation returns to normal. I removed the master cylinder cover when hot and the brake fluid level is just under the lowest screw cap threads. When cold, the fluid is lower. 

 

Is too much brake fluid level the cause and what level should it be filled to when cold? 

[TTR]

Please detail & refine what exactly "completely overhauled" in your world means.

The braking system like this is quite simple and straightforward to overhaul/rebuild/restore ...

... and I can't imagine any system being able to have "too much brake fluid".

 

 

Edited June 10 by TTR (see edit history)

[ericdev]

18 minutes ago, TTR said:

Please detail & refine what exactly "completely overhauled" in your world means.

The braking system like this is quite simple and straightforward to overhaul/rebuild/restore ...

... and I can't imagine any system being able to have "too much brake fluid".

 

 

New:  Brake cylinders, shoes, hoses (exc lines) & master cylinder. System had been thoroughly flushed and bled. 

[TTR]

Are the aforementioned components OEM correct for this application ?

Is/was everything assembled & adjusted correctly ?

Are there any aftermarket/non-OEM components or features added to the system ?

What about drums ?

Were they turned and was the each pair of shoes arc’d to fir their respective drums ?

What type of fluid was used ?
Etc, etc, etc …

[dalef62]

I would check the adjustment on the Master cylinder brake rod, it sounds like it may not have enough play and when things heat up under the hood it is pushing on the cylinder in the master cylinder and causing the brakes to drag. 

[pfloro]

Could the booster be the cause?  Sitting between the master cylinder & firewall, it will certainly absorb engine room heat...

 

Paul

[Harold]

Not to divert the focus of this thread, but 1959 and 1960 Cadillacs were the subject of a recall for the Pitman arm separating, which results in loss of steering.  The OP may want to check this on his car.  There are several discussions online about this topic.   Now, back to our regularly scheduled programming....

[ericdev]

1 hour ago, TTR said:

Are the aforementioned components OEM correct for this application ?

Is/was everything assembled & adjusted correctly ?

Are there any aftermarket/non-OEM components or features added to the system ?

What about drums ?

Were they turned and was the each pair of shoes arc’d to fir their respective drums ?

What type of fluid was used ?
Etc, etc, etc …

Everything has been done correctly; the system is stock and OEM correct parts were used. The car is an unrestored original with 46,000 miles and was on loan to the AACA Museum for the Survivor Car Exhibit that ran from 11/21 until 4/22. The mechanic who did the brake system has been doing all our mechanical work for nearly 50 years and has an antique car collection of his own of mid '50s Fords. He is one of the most experienced and meticulous techs you could ever hope to find. 

 

I'm mainly interested in hearing what would cause the pedal to become stiff accompanied by brakes remaining on when heat builds within the engine compartment.  For reasons I'd rather not go into, I'd like to try and solve this without getting him involved if possible but it may be unavoidable.  I just did some research and numerous sources online did say that overfilled brake fluid can result in exactly the symptoms I'm experiencing. 

Edited June 10 by ericdev (see edit history)

[ericdev]

42 minutes ago, Harold said:

Not to divert the focus of this thread, but 1959 and 1960 Cadillacs were the subject of a recall for the Pitman arm separating, which results in loss of steering.  The OP may want to check this on his car.  There are several discussions online about this topic.   Now, back to our regularly scheduled programming....

I am aware of that recall and the car had gotten the replacement Pitman arm. Thanks. 

[Bhigdog]

Not too familiar with 59 caddy system but pretty much every brake system manual or power has a compensating port in the master cylinder. When the brakes are not applied the port is open  allowing free flow of fluid between the resovour and lines to prevent fluid expansion from heat applying pressure. Just slight movement applying the brakes closes the port.

Back off the actuating rod to allow more free pedal play..............Bob

Edited June 10 by Bhigdog (see edit history)

[Frank DuVal]

2 hours ago, ericdev said:

  I just did some research and numerous sources online did say that overfilled brake fluid can result in exactly the symptoms I'm experiencing. 

It would have to be filled to the brim with no vent for this to happen. There has to be a vent in order to allow fluid to exit the master cylinder in order to apply the brakes. Yes, there are rubber diaphragms on most cars starting in xx year, with the vent on the other side of the rubber diaphragm. But, these master cylinders have room above the fluid level to expand into, while forcing the air above the diaphragm out the vent. Think the expanding bellows on GM cars of the 60s and later.

 

I too would look at the free pedal play in order to make sure the compensating port is being uncovered. Then again, is the port drilled through? You say it is a new master....😉

Edited June 10 by Frank DuVal (see edit history)

[Ed Luddy]

Sounds like you are losing your vacuum assist due to maybe a collapsed hose that then holds brake pressure? Just as guess but I would replace the brake booster and vacuum lines.

[pfloro]

8 minutes ago, Ed Luddy said:

Sounds like you are losing your vacuum assist due to maybe a collapsed hose that then holds brake pressure? Just as guess but I would replace the brake booster and vacuum lines.

I would try to isolate the problem by disconnecting the vacuum line from the booster and of course, plugging the manifold side.  Then, exhaust the booster vacuum by pressing and releasing the brake pedal several times.  Test at low speed on a quiet neighborhood street.  This would remove the booster from the equation.

 

Paul

Edited June 11 by pfloro (see edit history)

[Rusty_OToole]

I think Bhigdog has it. Pressure is building up due to heat and there is no place for it to go. Why this is happening, I can't tell, but usually it is not enough free play in the pedal rod.

[61polara]

All good comments, but you need to find out where the pressure is building.  Which wheels are locking up?  Then you can start diagnosing what is going on.  If it is all wheels, look at the master cylinder and brake booster.  If only one wheel, look at the rubber brake hoses to that wheel.  I've put new, NOS rubber brake hoses on a car before and have they fail on the next long drive because of internal swelling.  They looked fine on the outside, but I cut them open and they had swollen up completely inside and no brake fluid could return through them.

[TTR]

8 hours ago, ericdev said:

Everything has been done correctly; the system is stock and OEM correct parts were used. The car is an unrestored original with 46,000 miles and was on loan to the AACA Museum for the Survivor Car Exhibit that ran from 11/21 until 4/22. The mechanic who did the brake system has been doing all our mechanical work for nearly 50 years and has an antique car collection of his own of mid '50s Fords. He is one of the most experienced and meticulous techs you could ever hope to find. 

 

I'm mainly interested in hearing what would cause the pedal to become stiff accompanied by brakes remaining on when heat builds within the engine compartment.  For reasons I'd rather not go into, I'd like to try and solve this without getting him involved if possible but it may be unavoidable.  I just did some research and numerous sources online did say that overfilled brake fluid can result in exactly the symptoms I'm experiencing. 

First, there could be several potential contributors to your described problem, hence my request for additional details and information. And while some of these “potential contributors” could be heat related, many others are not. 

 

Second, if your mechanic is as highly “experienced and meticulous” as you believe him to be, he should be in the best position to advise, especially if he was the one who did all the work on this system, or at least, he’s likely in much better position to do so than any random stranger, including me, on this or any other forum.
Rest of us here or anywhere else on the interwebs are just “shooting in the dark” as the saying goes (but apparently won’t stop some pulling their triggers with myriad of suggestions). 
Besides, if everything was done correctly (as per factory repair/service/shop manual instructions & specifications) and using correct, quality parts, etc, the system like this shouldn’t exhibit any problems you describe and if it is, it’s impossible for me to see enough to adequately advise from where I sit.

 

Third, while I may not have quite the same length of experience as your mechanic (or is it “tech”, whatever that is ?), I’ve been rebuilding, repairing, restoring and working on vintage cars for about 45 years (nearly 40 pretty much full time) and can’t recall encountering, experiencing or even hearing about any reservoir overfilling directly causing braking problems until this thread.

I am aware of overfill spillage causing damages to refinishes on some components & parts, but never heard of “overfilling” directly causing mechanical/operational problems in braking systems.

Perhaps I need to spend more time with online sources to learn from those with more experience than I have ?

[John348]

The first thing I thought of when I read that the pedal becomes hard as the brakes become hot is that there is air in the system, and it needs to get bleed some more.

[Frank DuVal]

Nope, air makes the opposite effect. Air is compressible, therefore results in soft/low/to the floor type effects in a hydraulic brake system.😉

 

Now air in a booster, will result in a hard pedal. The more air the less vacuum there is.

[Restorer32]

18 hours ago, dalef62 said:

I would check the adjustment on the Master cylinder brake rod, it sounds like it may not have enough play and when things heat up under the hood it is pushing on the cylinder in the master cylinder and causing the brakes to drag. 

What he said.

[60FlatTop]

I did not see new brake hardware and springs listed in the replacement parts.  They are important.

 

Two things I do not trust are new parts and old mechanics.  Presented with this situation I would remove each new rubber brake hose. That car uses four as I remember. And run a piece of #10 electric wire through them just to be sure the inner lamination did not distort. All four. Those are still 1/4" hoses.

That car has a touchy adjustment. Tighten the adjusters and back off 19 clicks or something like that. One really needs to have a mindset of following instructions. Sometimes that can be a problem. Actually the reason I do most of my own work is because I do find and follow instructions. I have been quite disappointed by those claimed to have "forgotten more than I will ever know".

 

I have been intimate with two 1959 Cadillac's. There are not a car to be serviced by anyone who is easily frustrated.

[John348]

2 hours ago, Frank DuVal said:

Nope, air makes the opposite effect. Air is compressible, therefore results in soft/low/to the floor type effects in a hydraulic brake system.😉

 

Now air in a booster, will result in a hard pedal. The more air the less vacuum there is.

I disagree, my friend I have encountered the opposite as brakes the brakes got hotter

[JACK M]

The first test I would do is see if the pressure can be relieved by opening a bleeder valve.

[Ed Luddy]

9 hours ago, 60FlatTop said:

I did not see new brake hardware and springs listed in the replacement parts.  They are important.

 

Two things I do not trust are new parts and old mechanics.  Presented with this situation I would remove each new rubber brake hose. That car uses four as I remember. And run a piece of #10 electric wire through them just to be sure the inner lamination did not distort. All four. Those are still 1/4" hoses.

That car has a touchy adjustment. Tighten the adjusters and back off 19 clicks or something like that. One really needs to have a mindset of following instructions. Sometimes that can be a problem. Actually the reason I do most of my own work is because I do find and follow instructions. I have been quite disappointed by those claimed to have "forgotten more than I will ever know".

 

I have been intimate with two 1959 Cadillac's. There are not a car to be serviced by anyone who is easily frustrated.

As a former 1959 and 1960 Cadillac owner I fully agree with your last sentence! I will never drive one of them again with old stock brakes. They are a perfect example of too much weight vs. too little brake shoe/ drum surface.

[Frank DuVal]

10 hours ago, John348 said:

I disagree, my friend I have encountered the opposite as brakes the brakes got hotter

You found air to become non-compressible as it gets hotter?❓Sure as temperature rises the pressure rises, but no where near hydraulic pressure of a brake system.

[ericdev]

It turns out the brake booster is the culprit. Apparently an internal valve failed, resulting in the hard pedal/brakes-on condition when the fluid expands with heat. Thanks to everyone who contributed to the topic.  

[TTR]

@ericdev Thanks for reporting back and I’m glad you got it solved.

 

I’m still having difficulties understanding how the (expected/normal ?) heat or temperature changes in otherwise normally working braking system could create a fluid expansion causing (unexpected/abnormal) braking lockup or how a faulty vacuum operated booster could directly contribute to this.

OTOH, there are countless other things in this life and universe I’m still to learn and understand.

 

[Motorpirate]

if the booster is holding the piston in the master past the relief hole the expanding fluid can't flow back into the reservoir and it applies the brake. same as a too long pushrod on a manual brake set up.