Lyle_STL

Was driving yesterday and suddenly when going down a pretty short downward hill, the brake light on the dash started coming on once I gave the pedal max pressure. Reduced pressure and it goes off. But you had to apply a lot more pressure than usual to stop the car (pedal seemed to go near the floor, but not all the way down). Is it just a simple matter of the fluid being low (haven't noticed any new leaks), or something more serious? Note: I couldn't find the brake fluid reservoir... It's not easily recognizable like it is in modern cars.

oldcutlass

Check your fluid level. The master cylinder looks like this and is not hidden. Its on the drivers side right on top of the firewall. Just move the spring arm and lift the cap.

Lyle_STL

Thank you for the pic and instructions.
Should I be concerned if the fluid is low but I haven't seen any leaks?

Might be a dumb question... But I am assuming the OEM was 4 wheel drum brakes? Is there any easy way to tell the life they have left without removing the wheels (like the wear indicator sounds the modern brakes give)?

69 Ragtop

Not a dumb question at all. The master cylinder has little rubber cups that act as plungers. You can have an internal leak that doesn't leak to the outside. IIRC, it also can leak into the passenger compartment and get absorbed by the carpet and may not be easily seen. A third failure mode can be a leaky wheel cylinder near one of the four tires. It may not leak enough to cause a puddle, but it will cause the loss in pressure, will allow air to enter the system, and will turn the brake shoe area for that wheel into a goo ball without leaking appreciably to the outside world.

When the light comes on, it means that either the front braking system or rear system is not working correctly (i.e., one of the systems doesn't build hydraulic pressure like it used to). That causes a sliding valve in the proportioning valve to move out of it's "OK" position, triggering a switch that lights the light. You take your foot off the brake pedal and the pressure decreases. If the problem is not too bad, the valve returns to the "OK" position, causing the light to go out.

Most cars will have 4-wheel drums. I believe there was at least one option for front wheel discs. Someone with better knowledge of year-specific options will fill in my lack of knowledge.

On drum brakes, I've always pulled the drums to check the brake wear. I don't know of a slot to look through to tell otherwise. Once again, someone with more knowledge will add to this or confirm it.

JohnnyBs68S

Drums all around were standard on the F-85 / Cutlass / 442 in '68, front discs were optional. You need to remove the drums to properly inspect the brake shoes. This is easy on the rear, but a PITA on the front since the drums are a press-fit onto the hub. You have to remove the bearing grease cap, cotter-pin, crown nut and remove the drum with the hub / bearings to get the front drums off. If you have to replace the front drums, you'll need to press the hub out of the old drum.

From your symptoms, it could just be low fluid causing the brake light to come on, topping off the fluid would be a good test to eliminate that possibility. However you've probably already pumped air into the brake lines, so bleeding the brakes will be necessary once you find the leak.

Fluid levels will go down without leaks because the brake shoes wear (although this is an issue more with disc breaks than drums because drums are self-adjusting taking up most of the slop in the mechanism that is created when the shoes wear). For sure, I'd check the wheel cylinders and master cylinder for leaks if you are losing fluid.

oldcutlass

There is no such thing as just low when the brake light comes on, the pedal goes to the floor, and reservoir is low. It means there is a leak somewhere.

BackInTheGame

Eric,
Could it also mean that one or more individual wheel cylinders/shoe-sets are over-worn, thus keeping more fluid in the lines rather than the reservoir? (Just thinking out loud here - trying to learn.)

matt69olds

If the pedal is low but firm, check the brake adjustment. Just because drum brakes are self adjusting doesn’t mean anything if the hardware is crusty and sticky.

Assuming the wheel cylinders and lines are in good shape, clean/adjust the brakes, bleed the brakes, then take the car out for a drive to evaluate the braking.

oldcutlass

Worn shoes will lower the master cylinder reservoir level, but it won't empty the bowl to the point of the brake light coming on. As stated above, the brake system needs an inspection and possibly a brake job. The master cylinder can also leak into the power booster.

Lyle_STL

Great detail! Thank you!
I'm gonna top off the near empty rear reservoir and see what happens.

Lyle_STL

Fingers crossed that the fluid refill does the trick.

Lyle_STL

Afraid of that. That means the dreaded trip to the mechanic.

Lyle_STL

That was my next question was other than the obvious brake light and low/empty reservoir, what signs do I have that the brakes are getting too worn?

Lyle_STL

I found the rear reservoir was nearly empty.

droldsmorland

Pull the rear drums. You will likely see brake fluid coated shoes due to a leaking wheel cylinder.

I've been reading other posts you have made. Is this your first classic car or has this car been sitting for a long duration?

The whole brake system needs to be freshened (likely). This includes a full system flush, replacing the 3 rubber flexible lines, and whatever else needs servicing. This is a safety issue. While the front drums are off repack the wheel bearings.

How old are your tires?

Brake fluid should be flushed every 3-5 years. Pay attention to all the cars fluids. If you don't know when the fluids were last serviced do all of them.

Lyle_STL

First classic car, and I wasn't born when they were originally on the road. Lol

Tires looked newer when I bought the car 3 years ago. Car is rarely driven. Once or twice a month had been the average.

Tedd Thompson

X2 on the booster robbing the fluid as Eric said and often there won't show any sign of leaking. Don't think just because you topped it off and got some brakes that all is well. That fluid went somewhere best to find out where, check all possibilities before you risk life and limb...... Tedd

droldsmorland

Long read sorry. Don't feel any animosity towards the question I asked about this being your first car. We need to hand this culture off to the next-gen and you're it!

As mentioned the master could be leaking into the brake booster if it has power brakes?

If you have a decent set of basic tools you can perform much of the service with proper guidance patience and YouTube.
If you don't have access to a good set of jack stands and floor jack you might want to look into it. Sears for both while they are still in business?
Harborjunk is last on the list for the most part. Estate & garage sales...Craigslist..facebook classifieds are where you can get the good USA stuff cheap.

Purchase all of the manuals for the car. There are at least 4. Body, Chassis, Assembly and Service.
They are not too expensive and will be a great resource to you and us when we refer you to something.
These cars are fairly simple compared to today's cars. Pictures uploaded here are highly recommended. We'd also like to see your ride.

80% of what you will need is available for this car. Routine maintenance parts are still abundant. Rock Auto. Local NAPA and Mom & pop parts stores.
Don't trade-in any parts off this car for the core charges. Save them or have them rebuilt. Big Box store rebuilt parts are hit n miss today.
68 is a one year wonder for some parts. Fusick, Year One, OPGI, and a few others will have restoration parts. Ask as there are a few to stay away from.

I'd suggest getting involved with the local car cruise nights(when we don't have to distance) and local Oldsmobile clubs. You will find a lot of like-minded people willing to lend a hand.

You need to find a reliable shop or car guy who can help make the repairs. This person will be able to inspect it too. If your state requires annual inspections you will really want to find a local mom n pop shop to inspect it. Don't trust the dummies at the big box stores.

You should have the chassis inspected on a lift by a good mom and pop shop. Steer clear of the big box repair shops. Rarely will you find a mechanic competent with classic cars?

Tires can look new and be 20 years old. There is a DOT date on the tires. Older than 10 replace them...not worth a blowout. Tire Rack explains where & how to interpret it.

Attached is a list I made to pull a car out of hibernation. Not all of it applies, but you could use it as a guide of things you need to pay attention to for safe reliable cruising. Concentrate on safety first then do the pretty shiny stuff.