Here's how to approach it:
1. Locate the Master Cylinder: The master cylinder is the heart of the braking system. It's likely under the hood, but its exact location varies by car model. It's typically a relatively large cylindrical unit with brake lines leading away from it. Look around the firewall area, often near the brake pedal linkage, but don't assume it's in a specific spot. A 1956 shop manual or online forum dedicated to classic Oldsmobiles (like the Oldsmobile Club of America's forum) will be invaluable here. Pictures from others who've worked on their '56 88 will help immensely.
2. Once Located, Check for Fluid Level: The master cylinder will have a reservoir on top. This reservoir may have a small cap that needs to be removed. Look for a visible fluid level. The reservoir will likely be made of metal, possibly painted. It may have markings indicating minimum and maximum levels.
3. Inspect the Fluid: While you have the cap off, look at the brake fluid. It should be clean and clear; dark brown or black indicates contamination and needs flushing. If it's significantly low, it needs to be topped off *immediately*.
4. Adding Brake Fluid: If you need to add fluid, use DOT 3 brake fluid only, as recommended for older vehicles (check your owner's manual or a reputable parts supplier for confirmation). Do not overfill, stick to the level markings on the reservoir.
5. Important Considerations for Older Cars:
* Leaks: Low fluid level often points to a leak somewhere in the system – a line, hose, wheel cylinder, or even the master cylinder itself. Simply adding fluid won't solve the underlying problem; find and fix the leak.
* Corrosion: In an older car, corrosion is a real concern. The reservoir itself might be rusted or damaged, and the brake lines may be deteriorated. Regular inspections are crucial.
* Manual: A 1956 Oldsmobile 88 shop manual will provide diagrams and specific instructions for your vehicle. This is the most reliable source of information.
Safety First: Brake fluid is corrosive. Wear gloves to avoid skin contact. If you are unsure about any step of this process, take your car to a qualified mechanic experienced with classic cars. Improper brake maintenance can be extremely dangerous.
