Checking fluids under the hood takes you a step deeper in your car experience. There are several different fluids that your car has and I’ll go over them here. I’ll also cover generally how to find them and what they look like.
All cars will have brake fluid. If your car has a gas engine there will be engine oil, and coolant (or antifreze). Some full electric vehicles have coolant as well to keep the motor (not engine) and electronics from overheating.
If your vehicle has power steering you will have power steering fluid. Vehicles with automatic transmissions will have ATF (automatic transmission fluid). Some manual transmission vehicles will have a hydraulic clutch which uses brake fluid.
Cost: Most fluids are about $3-6/quart.
Brake Fluid
The brake master cylinder on most vehicles is on the engine side of the firewall. It will be on the firewall right in front of the driver. The brake master cylinder has a reservoir connected to it. Most of the time the reservoir is mounted directly on the master cylinder but sometimes it is remote.
There usually is a set of Min and Max marks on the reservoir. Make sure that the brake fluid level is in between the Min and Max marks.
If the brake fluid is close to the Min mark this can indicate a couple of things. If you haven’t noticed any braking performance reduction then it probably just means that the brakes are getting low. As the brakes wear the calipers require more fluid. This shows up in the reservoir as a lower fluid level.
You may want to check to verify that your brakes have an adequate amount of material on them so that you can remain safe.
WARNING: If your brake fluid is low DO NOT just add fluid. This can end up being a costly mistake. At best you could go metal to metal on your brakes. This is costly in that you will have to replace your brake pads as well as brake rotors. This can double the price of a brake job. At worst, if your brakes are under spec then you could be creating a situation where you won’t be able to safely stop. The cost of an accident can’t be estimated.
Engine Oil
Engine oil typically has a dipstick that it registers on. You will need to check this when the engine has been off for at least 10 minutes. Check this on level ground so that the reading is accurate.
Make sure that the oil reads between the low and high marks. These marks usually denote a one quart difference. Read my Preventative Engine Maintenance 101 for an in-depth explanation on how to check your engine oil.
Coolant
Most vehicles that utilize coolant will have an overflow bottle that is marked with H (high) and L (low). Some coolant overflow bottles will be labeled that they contain coolant, and some aren’t labeled.
Coolant expands and contracts based on how hot it is. If your vehicle is hot from just being driven the overflow bottle may read higher than when it’s cold from sitting overnight.
I recommend checking it when it’s cold. If it’s low I top it off to the H or High mark or make a note of where it’s at. You could take a picture with your phone or take a pencil and mark the bottle. Then a few days or a week later, check it again when it’s cold to see if the level has changed. If anything it might go down.
If the coolant is going down consistently, you should start to look for a leak under the vehicle.
Coolant comes in many different colors. Green/yellow, pink, orange, red, blue, and purple. Some coolant colors can be mixed and others cannot. You will need to check your owners manual to verify what coolant your vehicle takes.
Checking this fluid can help prevent your vehicle from overheating in the summer. Also it can prevent your vehicle from not heating up enough in the winter.
WARNING: Don’t confuse the overflow bottle cap with the radiator cap. Never open the radiator cap when the vehicle has been driven recently. If you do you will be on the receiving end of a scalding. The fluid in the radiator typically runs about 180-200 degrees and is under pressure. If your engine is overheating that temperature could be even more.
Power Steering Fluid
Vehicles with power steering (PS) will have a power steering pump and reservoir. The power steering pump will be driven by one of the drive belts or the serpentine belt.
In some vehicles the power steering reservoir is mounted on the pump. In other vehicles it is mounted remotely on the fender. If it is mounted remotly it will have a couple of hoses connecting the two.
The cap on the power steering reservoir should have a short dipstick built into it. Some vehicles also have a translucent reservoir with markings on the outside. They may have a mark for “cold low” and “cold high” as well as a “hot low” and “hot high” mark. If the vehicle is cold the level should be between the “cold” marks. If the vehicle has been driven recently the level should be between the “hot” marks.
Some vehicles with power steering use power steering fluid. Others use automatic transmission fluid. Check the lid of the power steering reservoir or your owners manual to see which your vehicle uses.
If you need to add some just add a little. Most power steering reservoirs only hold 1-2 cups, so adding a tablespoon or two will make a big difference in this under hood maintenance. Add some fluid when the engine is off. Replace the lid and then turn the engine on and cycle the steering wheel from far left to far right. Turn off the engine and recheck the fluid. Repeat as necessary.
WARNING: Don’t leave the cap off when you are cycling the steering wheel. The pressure of the return fluid will blow fluid all over your engine bay. This won’t only make a mess, but also make it so that you will be lower on fluid than you were.
These next two are an either or for your car. You may have a manual transmission with a clutch or an automatic transmission. The exception would be if you have a manual transmission with a mechanical linkage clutch. This doesn’t happen much anymore, but there are vehicles out there with this configuration.
Clutch Fluid
If your vehicle has a manual transmission and an hydraulic clutch you’ll look on the left side of the brake master cylinder.
Note of clarification on directions. It is common for mechanics to reference left and right when talking about where something is on a vehicle. Left refers to the left side of the car as if you are sitting in the drivers seat and right is the opposite side. In America the driver sits on the left side of the car and in England the driver sits on the right side of the car.
So just left of the brake master cylinder will be a similar looking, but smaller cylinder with a reservoir attached. This is called the clutch master cylinder.
There usually is a set of Min and Max marks on the reservoir. Make sure that the fluid level is in between the Min and Max marks. The clutch usually takes the same fluid as the brakes. The difference here is that if it is low you will want to add some to get it back to the Max mark.
Also, if it is low, you will want to start looking for the leak. It could be under the dash or under the vehicle if it isn’t right there at the clutch master cylinder.
Automatic Transmission Fluid
If your car is equipped with an automatic transmission then you will want to check the fluid level and condition. Automatic transmissions are super complex and I won’t go into all the details of how they work here. This is the most complex fluid check you wil do besides the checking oil.
Most vehicles with an automatic transmission will have a transmission dipstick. Some late model vehicles don’t have a transmission dipsitck or any way to check the transmission fluid level. Check your owners manual to verify if your car has one and where to find it.
Make sure that you’re on level ground so that the dipstick reads accurately. The dipstick will have a hot range and a cold range for measuring the fluid level. If the vehicle hasn’t been driven then it should read in the cold range. If the vehicle has been driven and is to full operating temperature the the fluid level should read in the hot range.
Simple How-to check ATF:
- Open the hood and find the dipstick.
- Once you find the dipstick you will want to start the vehicle and run it through all the gears. Don’t move the vehicle, just make sure that the transmission is shifted into all of the different shift lever positions.
- Put the transmission back in Park and leave the engine running.
- Pull the dipstick and wipe it off.
- Reinsert it fully and then pull it again, but don’t wipe it off this time.
- Look at the fluid level on the end of the dipstick.
- Verify that the level is in the appropriate range (cold if it hasn’t been driven or isn’t up to operating temperature, hot if it has been driven and is up to full operating temperature).
- Look at the fluid to see if it is very dark or smells burnt. If this is the case it may be time to replace it.
If you are not sure when to check or change your fluids click below to download my Car Care & Maintenance PDF today.