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How to Safely Check the Coolant in Your GM

Engine coolant is essential for keeping everything in your GM working properly and to prevent it from overheating. Every now and again, it’s worth checking your coolant level to make sure that it’s within the correct levels, and if not, top it up. This guide will show you the safest way to check your levels and ensure you top it up correctly.

1. Make sure the engine is cool when you’re checking the levels.

This is the most important step. The fluid that is contained in your cooling system can run at very high temperatures and pressures. Always make sure the engine has been turned off for at least a couple of hours, ideally longer.

2. Make sure you have purchased the correct coolant for your car.

Different cars or trucks require different coolants for their systems. Check your owner's manual or speak to your dealer to find out which is the correct coolant for your vehicle.

3. Check the reservoir.

Most modern cars come with an external reservoir connected to the cooling system. On this, there should be two markings: “Max” and “Min”. If the coolant level is anywhere between these two markings, then your coolant level is correct

When you check the levels in the external reservoir, make sure the vehicle is parked on a flat surface (and as described above, the engine must be cool). This will give you a more accurate reading on your levels.

4. What low coolant can mean

If you see that your coolant level has fallen below the "min" mark in the external reservoir, you'll need to add some coolant.

However, before you start pouring coolant into the external reservoir, it's a good idea to figure out why coolant is disappearing.

  • First, check for system leaks.
  • Second, check your exhaust for white smoke. You can do this by asking a friend to follow you. If you step on the accelerator and your friend observes a lot of white smoke coming out of your exhaust pipe, you likely have a head gasket problem.

NOTE: There's a difference between white smoke and steam. All vehicles will emit steam on cold days, especially if they haven't had a chance to warm-up yet. If your exhaust is producing white smoke on a warm day, and the engine is warm, than you've probably got a head gasket issue (or something that's causing coolant to enter the combustion chamber).

If you can't find a leak or don't see white smoke, keep an eye on coolant levels for the next few weeks and see if it falls any further.

Also, follow the instructions in your vehicle's owner's manual before adding coolant to your external reservoir tank. On some vehicles, coolant is poured directly into the radiator. On others, you pour the coolant into the external tank.

Finally, check the coolant that you are using before filling as well. Some products may need diluting prior to being added.

5. Topping up.

Should your vehicle need some extra coolant, then add it to the reservoir to get to the “min” level (or just above). Do NOT fill the overflow tank to the "max" level. This is over-filling your cooling system, and that can cause a lot of problems. Coolant expands as it's heated, and the overflow tank is designed to accommodate the expansion. If you fill that overflow tank to the MAX level, your hot coolant is going to expand beyond the confines of the system (and that's obviously bad).

6. Double-check your work.

Cooling systems aren't necessarily tricky, but you don't want to make a mistake over-filling, or forget to replace or properly tighten a radiator cap, etc. Take your time, verify all the steps, and you're good to go.