Power brake booster

[mickey56]

On a 59 62 series Does the  booster hold vaccum with the engine off?  I isolated the reserve tank and tested
it with an external source (engine out of car)and it holds vac. Did the same with the booster,
but it leaks off.
I would assume it should hold also.  Any advise would be appreaciated.

[dplotkin]

You should have a check valve to hold the vacuum in the can and reservoir. On 50+ year old cars original check valves are shot.

Dan

[mickey56]

I was testing each component separately. The storage tank will hold vac. when tested.
The booster leaks off in maybe 15 sec. The check valve isn't connected/tested separately
and holds vac. Its a bendix unit and according to the shop manual it can be disassembled
and cleaned but I didn't see a testing procedure.

[dplotkin]

The booster should hold vacuum but probably not indefinately. Given the perishable/consumable nature of boosters (the life of which is shortened by a leaking master cylinder rear seal) if your booster is off the car I would send it out and have it re-done along with the master cylinder and never worry about it again. Not expensive and the improved pedal feel and peace of mind are worth it.

Ed Strain did my 60 Buick which I believe is the same setup as on the 59 Cadillac.

Dan

[J. Gomez]

I was testing each component separately. The storage tank will hold vac. when tested.
The booster leaks off in maybe 15 sec. The check valve isn't connected/tested separately
and holds vac. Its a bendix unit and according to the shop manual it can be disassembled
and cleaned but I didn't see a testing procedure.

Assuming your topic relates to a 1956 Bendix unit, the repair manual section 7 page 3 explains the operations and functions of the unit. Vacuum should be held by the vacuum poppet valve (see diagram on page 3), if your leaks in 15sec, I would suspect this valve is defective.

Good luck..!

[dplotkin]

The 56 unit is altogether different from the 59, but the same theory applies.

Dan

[mickey56]

Thanks for your replys. I studied those drawings (fig 8-1 & 8-2 in my book ) and could send
it out for repair BUT I'm like a kid that takes his mothers mixer apart to see how it works.
So I may disassemble it to see if dirt got under that valve creating a leak. Can't hurt it, its allready
broke. I just need to know.  Thanks guys  I'll let you know how it works out.  I love a challenge !
       

[mickey56]

Good morning
I dissembled the booster and found some rusty areas in the cylinder area so i cleaned
it up with some fine sandpaper. It appears that it was refurbished once before. Two things
i did notice was the brake light switch was adj. down to where it held the pedal down about
a 1/2 inch holding the poppet valve open and the O ring on the master cyl. was damaged.
I replaced the O ring and adj. the switch and now when the brake is applied you can hear
the booster moving in the bore. A professional rebuild will come later but for now its working.
Another thing i want to check is the brake shoe adj. I see theres no self adj. hardware on these
old cars. If i get the wheels adj. up i think ill be in good shape.
Any wisdom you guys could pass along would be greatly appreaciated   THANKS