This 1955 Olds Super 88 is new to me. I did have one of these back in high school but that was when the car was only 6 years old. The problem on this one is that the brake pedal is on the floor or nearly so. When applying pressure to the pedal sometimes the car stops and sometimes it doesn’t. I’ve been reading all the stuff I can find about this and have narrowed it down to one of two things. There is either a vacuum problem somewhere or the Bendix treadle vac system is on the fritz. Am I on the right track? Or does some other system make more sense. HELP!

 

Make sure the master is full of fluid and check wheel cylinders for leaks and adjust brakes. Then you will know

 

I'd say the most likely problem is a bad master cylinder.

 

I'll add that just because the M/C is full doesn't mean that the seals inside the M/C are any good. If the piston seals leak, the pedal goes to the floor without building any pressure.

 

The master cylinder is full. Will check the wheel cylinders, shoes, and drums next. Drove it today around the block and the brakes seemed to be working - they stopped the car - but the lack of pedal travel is a bit concerning.

 

The pedal travel could be brake adjustment

 

As near as I can tell, and I don’t have a lot of experience here, the master cylinder is part of the Bendix treadle vac system. I’m guessing that if there are bad seals they are inside that unit. There doesn’t seem to be any brake fluid dripping out when I exercise the brakes in the garage. But I suppose it could be leaking past the seals and stay inside the unit. Does that make any sense?

 

Yes

 

Hydraulic seals are in the M/C, not in the treadle vac. The M/C still has a piston with a rubber cup just like any other brake M/C. If that rubber cup is worn, the M/C won't push fluid to the wheels effectively. Obviously check the easy stuff first, like brake adjustment at the wheels, but a worn M/C cup won't cause an external leak.

 

If it goes to the floor, that fluid is going somewhere. If you have NO brakes, then it may be puking it out the back of the MC. I have had this happen.

 

An internal leak in the M/C where fluid gets past the piston cup won't necessarily become an external leak. Fluid behind the cup ends up back in the reservoir. I had a situation on one vehicle (on a dual-circuit M/C, admittedly) where an internal leak caused fluid to flow from the front reservoir to the rear one. The level in the front reservoir went down, the rear went up, and there was no external leak. And yes, it is also possible for fluid to leak out the back and into the booster, especially under vacuum conditions.

 

If it is the treadle vac, I recommend karps power brake service to rebuild it. They did mine on my 57 olds. They did a great job on it

 

Have you tried checking the vacuum hose at the carb and at the tank(left hand side next to the frame rail) for loss of vacuum? If there is a leak any where in the system that will happen( foot to the floor). Interment brakes are worse than no brakes at least with no brakes you know what's going to happen....Tedd

 

I drove the car around town this morning after getting a 60 day tag. Went to Casey’s to get no alcohol gas and the lady who works there came all the way out of the store to look. The brakes worked fine but they still have very little pedal travel. Is that normal in a 55? I plan to replace every vacuum line I can find so if there are leaks, that should fix that. I’m going to start checking the shoes and drums this afternoon. I know how to do that work but I don’t know how to check the seals in the master cylinder. So a little help on that would be appreciated.

 

If there are any leaks it will be inside the master cylinder you won't be able to see them You might have to end up rebuilding it

 

The Tredle-Vacs didn't have as much pedal travel as most modern cars . If they work OK , you should be fine .

Do you have a 1955 Oldsmobile Shop Manual ? Everything you need to know about service and adjustment .
Available on E-Bay , original printed copies are best ;
1955 OLDSMOBILE SHOP MANUAL SERVICE BOOK ORIGINAL RARE OEM REPAIR GUIDE | eBay

 

Most treadle vacs don't have much pedal travel, that is normal

 

I do have the shop manual. It’s a little vague on some things - at least to a rookie like me. I’ve only had time to look at one brake. It looks like somebody did a brake job before I got it. The shoes look new and the drum is smooth. There is no evidence of leaking fluid at that wheel. Grandkids are here now for a couple of days so it looks like repairs will be on hold for a few days. They did enjoy a ride this evening, especially excited because there were no seatbelts.

 

No seat belts don't compare to climbing up on the rear window shelf or playing on the rear floor and all the other things you can do with all that room.