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Six Fluids That Should Be Checked Regularly in a Classic Car

Fluids are the life force of every vehicle. This is especially true for muscle cars, hot rods and classic cruisers. Without the proper levels you might find your prized possession seized up or overheated on the side of the road.

That’s why it is essential to regularly check these six fluids… or at a minimum, the first four.

Motor Oil

Second only to fuel, motor oil is the most important fluid to any vehicle. Without it, a combustion engine wouldn’t be possible. It is responsible for lubricating parts that rev thousands of times per minute.

To check your oil, locate the dipstick in the engine bay when the engine is cold. Pull out the dipstick and clean off any oil in order to get a clean reading. Now slide the dipstick back into the tube and seat it firmly back in place. Pull the dipstick out again and you will now be able to see if your engine is low on oil.

Typically, most dipsticks have a full and low measurement range. If the oil line is within the safe zone, you are OK to drive. It’s best to keep the oil level towards the full line. Check this level at least once per month. Definitely replace the oil every 2,000 miles just to be safe and replace the oil in the beginning of the warm season if your vehicle has been in storage through winter.


Without it, you might be able to start the car, but it isn’t going to run for very long. Coolant (antifreeze) is what helps the engine operate at an acceptable temperature. With the help of a radiator, coolant is able to absorb the heat and then dissipate it. If you run low of coolant, it is likely you will have overheating issues.

On most classic cars and trucks, you can check the coolant level by removing the radiator cap. ALWAYS make sure the car is totally cold before removing the radiator cap. A lot of heat and pressure builds up within the cooling system and can take some time to reduce to a cool, safe level. Take extra care when removing the cap to avoid injury.

Once removed, most vehicles will show a fill line inside the neck of the radiator. Some vehicles might use a float to show the fill line and some radiators may have an overflow/expansion tank with fill lines. Just make sure you keep the coolant topped off. Its a good idea to check it when first firing it up for the season and at least once every month before going on a cruise, just to be safe.

If you still have overheating issues, it’s probably your thermostat. We recently wrote an article about the importance of having the correct thermostat in your classic car.

Brake Fluid

OK, so we have the oil and coolant levels in check and the car is driving smoothly. Now, can it stop? That is probably a question you want answered before you ever head out. Brake systems are a closed system which means you should never be low on fluid. If you find that you are low, fill it to the proper level and keep a close eye on it. You may have a leak or your brake pads could be wearing down.

In many cars the easiest way to check brake fluid is to look at the brake reservoir. It is typically a translucent white tank that allows you to see the fluid level. It is often located on the driver’s side of the engine compartment. Simply remove the top of the master cylinder and add fluid to the fill line. Make sure you use the correct fluid for your vehicle. Typically DOT 3 or DOT 4 fluid.

If you need to flush out the old brake fluid, it is a fairly simple procedure. Check out this video from Eric the Car Guy. He does an excellent tutorial on how to change your brake fluid. This should be done at least every 20,000 miles or at anytime you feel the brakes are feeling a little weak.

Transmission Fluid

Transmissions are similar to brakes in the they are both closed systems. This means you should never be low on fluid. If you are, you might want to have your tranny looked at by a professional. They are very complex and unless you know what you are doing, you’re best off to leave transmission work to the experts.

If your vehicle has a dipstick for the transmission, you can check it much in the same way you would your oil. The difference is that your vehicle should be running when you do. Transmission fluid should look clean and be a glossy red color. If it looks (or smells) burnt, looks dark or dirty, then it is time to have it replaced. If you need to add fluid for some reason, locate and pour it into the fill tube (Your vehicle may not have one) .

Power Steering (Not all classics will have this)

If you are lucky, you will be able to check your power steering fluid from time to time. If not, then you are gonna get an upper body workout driving your ride around. Power steering, which is an upgrade for many classic cars and trucks, pressurizes the fluid in a hydraulic system and makes it much easier to steer.

There shouldn’t be too many times that you need to check this fluid unless you hear or feel an issue with the steering. Otherwise, once or twice per season is usually sufficient. To check the levels, like many other fluids, there is a dipstick involved. Unscrew the cap on power steering reservoir and there should be a dipstick attached. Alternatively, there may be a translucent reservoir showing fluid with marked lines. Either way, just make sure the power steering fluid is between full and the minimum level. Make sure you use the power steering fluid that is meant for your power steering system.

Windshield Washer Fluid

The earliest documented idea for having a windshield wiper unit hooked up to a windshield washer fluid reservoir was in 1931. Therefore, most classic cars should have this setup.

Running out of washer fluid isn’t the end of the world, unless you can’t see the end of the world coming at you through a dirty windshield. In all seriousness, there isn’t any issue with it running out, but it’s a good idea to keep it full anyway. There really isn’t any way to overfill the washing system, so just keep the washer reservoir topped off and you should be good to go.

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