1955 Caddy no Brake pedal pressure

[caddyRay]

hi Cadillac Brothers
i purchased a 1955 Caddy about a year ago, my first Caddy ever. it has been sitting during the winter but starting driving it the last few months. up until a few weeks ago brakes were working fine yet, today i have no Brake pedal pressure at all, pedal falls straight to the floor.i am not all familiar with this type of Caddy brake system which has the original power booster, appears to have been rebuilt but not sure.i think this is called a Hydro Vac system and am learning this for the first time. there also appears to be a slave cylinder, maybe a master cylinder down by the firewall. i see no leakage from either unit but my brake pedal has zero pressure. not sure what to check or where to start. dont even know how to check the brake fluid level or even if you can..sorry this system is all new to me .any help that can be provided is aprreciated
rharms

[Jeff Rosansky CLC #28373]

Greetings.
A little background.
The cylinder under the floorboard is the master cylinder. Fluid/pressure comes from the master to the booster which is mounted opposite the generator then to a small manifold and out to the wheels. On the far left side of the firewall is the fluid reservoir. It is a skinny metal cylinder with a cap on it. You can follow the tube down to the master.
Take the cap off the reservoir  (3/4 I think but not sure) and see if there is anything in there. Probably not if your pedal is dead. Something happened in the system. You need to look at the master, booster, manifold and wheel cylinders for leakage. Something should be very wet if you went from a driving car to nothing. Check the rubber lines too (3 of them). Do this and report back. Please remember brake fluid eats paint.
Good luck
Jeff

[Mike Josephic CLC #3877]

Jeff is quite correct.

I'd like to add a couple of points.  Be sure to follow
each metal brake along the frame to all four wheel
cylinders.  Where they are clamped to the frame is a
great place for rust to form.  If you blow a brake line
you will have no brakes -- just what you are seeing.

Also, remember that this is a single master cylinder
and unlike a dual (modern) system if you have a leak
anywhere there is no back up!

Mike

[Jeff Rosansky CLC #28373]

Couple more things.
Mike is correct about the hard brake lines and the single system.
Also, as you don't see anything leaking at the master look at the inside if the wheels to see if there is evidence of fluid leakage. If not then pull the vac line from the booster to see if it is wet.
If you pull the wheels off please remember left wheels, left threads.
Jeff

[caddyRay]

I checked my brakes and think I have the cause for no pedal pressure as the passenger front drums has a leaking wheel cylinder, it was quite wet throughout the backing plate. rather than rebuild it I'm thinking it best to replace the entire wheel cylinder.the drivers side wheel cylinder was perfectly dry, rears seems fine. something odd was the drivers side adjustment hole for the brake tool to adjust the wheel is totally in the wrong spot,at first I thought whoever worked on it may have used the wrong backing plate, but I think the problem is the adjustment star unit has been put in reverse since the star does not line up with the hole. meaning this brake was never adjusted forcing the other brake to do all the work resulting in wheel cylinder failure on the other side(just my guess)so I need to replace the wheel cylinder but I have never bled brakes with the Hydro Vac system(not the normal dual reservoir common today)  I've found some but limited info on line on how to do it, I see there are 2 bleeder screws..any info on bleeding this type of system is appreciated

[Jeff Rosansky CLC #28373]

I fugured you would find something like that.
The manual will tell you. You bleed the booster 1st and then the wheels.
Now, replace all the wheel cylinders-or at least rebuild them. If 1 failed then the others are not far behind. This is a single system so you need to be cautious. They are not that ezpensive. However today, tomorrow and Wednesday you need to soak the brake lines at the cylinder to get them off.
As every job includes the "Might as Wells" I would look at all 3 rubber brake lines now. If in any doubt replace them too.
Jeff

[bcroe]

With a single system, everything needs to be in perfect shape.  I try
to replace cylinders and hoses every couple decades.  Lines get
replaced with something corrosion proof, stainless steel or the new
copper nickel alloy.  To see this happening, drop by.  Bruce Roe

[Jeff Rosansky CLC #28373]

To see this happening, drop by.  Bruce Roe

Would love to. Where are ya and can I go thru your trash for parts before I leave?
Jeff

[bcroe]

Would love to. Where are ya and can I go thru your trash for parts
before I leave?  Jeff   

I'm 7 miles west of the Rockford, IL airport.  Parts are mostly 77-79,
am trying to clean house.  Need a switch pitch TH400?  Bruce Roe

[Jeff Rosansky CLC #28373]

Wish I knew.... we took Dad's Comanche to Rockford a couple of years ago for some work. Would have bought you a cup of coffee. Maybe next time.
Jeff

[caddyRay]

hi Guys Thanks for all your info on 1955 Caddy Brakes since this is my first Caddy and wasnt at all familiar with the Hydro Vac Brake system.I think i will replace all 4 wheel cylinders which is sound advise. is the HydroVac system fairly reliable or is it worth swapping it out for a modern dual reservoir type ?

[Jeff Rosansky CLC #28373]

There is a lot more involved than you think to change that system. Besides, cars have been driving with them lake that for literally 100 years.
Jeff

[caddyRay]

when bleeding brakes on a 1955 Caddy with the Hydro Vac system do you use standard regular type brake fluid ,you buy off the shelf? or does the Hydro Vac system require some kind fo special brake fluid ?

[Dave Shepherd]

Dot 3 or 4 will do.

[Caddy Wizard]

The 55 single piston master cylinder gives no redundancy.  So if a brake line springs a leak, a seal fails in the master, or a wheel cylinder fails catastrophically, you lose all brakes at once.  I have noodled on this for quite a while and can see no good way to convert the car to a dual master and maintain any semblance of originality.

The best thing to do with these brakes is to go overboard since the car sits a lot and sitting is bad for brakes, generally.  So that means new STAINLESS STEEL lines, new rubber hoses, rebuild the old wheel cylinders and have them sleeved with brass or stainless steel, rebuild the booster and master (and have sleeved with brass or stainless).  Then use the car regularly and flush out the brake fluid every couple of years (brake fluid is hydrophilic, meaning it will absorb moisture out of the atmosphere, leading to corrosion and failure unless you take these precautions).  If properly overhauled and maintained, the original single circuit system can be made to be reasonably safe.  Not as safe as a dual circuit system, but reasonably safe.  I trust 'em when they are done up like that...

[Jeff Rosansky CLC #28373]

I rigged up a little pressure bleeder and bled them from the master down. You could do something like this and just leave it pressurized to look for leaks. Then I would just open each bleeder and it bled without having to pump. Used a garden type sprayer that you pump up and then some fittings to attach to the reservoir.

[bcroe]

There is a lot more involved than you think to change that system. Besides,
cars have been driving with them lake that for literally 100 years.
Jeff 

Pressurized master is claimed to work well.  I have seen an article or
two on how to build one, even got the parts on my shelf.  But never
had enough problems to get it set up and use it. 
Bruce Roe