How to Test Your Coolant/Antifreeze

Most drivers may never have given much thought to how well their car’s coolant/antifreeze is protecting the engine. But with winter on the way, now is the ideal time to test the fluid’s effectiveness and make sure your car is fully protected going into the coldest of seasons.

But how exactly do you test coolant/antifreeze? Surely it’s a job best left to the professionals, right?

Actually, testing the quality and performance of your car’s coolant/antifreeze is easy, and you can do it just a couple of minutes with the right tool.

This guide will show you how to check your car’s coolant/antifreeze, so you can be confident your engine is fully protected in all conditions.

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How to Test Your Car’s Coolant/Antifreeze

Stop! Don’t go any further! Is your car cool? If not, you risk burning yourself, so make sure the engine has been switched off for a good while before you do anything to the cooling system.

Before you test the coolant/antifreeze, it’s worth giving it a visual check, as this can tell you a lot about its condition and whether there’s a problem.

Something you should be doing regularly anyway, start by checking the coolant level on the side of the reservoir.

Ideally you want the coolant sat on the ‘max’ fill line, so if it’s not, top it up and check daily to see if the level has changed. If the level drops, the system may have a leak – in which case it’s time to call the garage.

Is the level OK? Then you’ll want to look at the coolant itself. What colour is it? Does it look dirty or discoloured? Can you see bits floating in it?

Antifreeze coolant recovery and expansion tank for radiator cooling system with low level of pink antifreeze

It’s not that easy to check the condition of the coolant/antifreeze through the reservoir tank. So to have a proper look, you’ll need a coolant/antifreeze tester.

A coolant/antifreeze tester is essentially a pipette attached to a small container. You can use it to get a sample of coolant from the reservoir.

Once you’ve extracted some coolant, the tester’s in-built gauge will show you the level of freeze protection the fluid is offering. And because the container is see-through, it’ll be easier to look at the condition of the coolant.

If it looks cloudy, dirty or full of particles, or if the freeze protection is down on the gauge, we’d recommend flushing the system and refilling with winter-ready coolant/antifreeze.

So to recap, here’s a quick guide on how to test your car’s coolant/antifreeze:

  1. When the engine is cool, perform a visual check of the coolant/antifreeze in the reservoir. Is it topped up to the ‘max’ fill line? What does it look like?
  2. Open the reservoir cap to take a sample of coolant/antifreeze. It’s vitally important that you do this when the engine is cold, otherwise you risk burning yourself from steam.
  3. Using a coolant/antifreeze tester, take a small sample from the reservoir. Close the reservoir cap while you check the coolant to prevent dirt getting in the system.
  4. Check the coolant in the tester. What is the freeze protection level and how does it look? If there are any signs of dirt or particles or its protection is fading, it’s worth replacing it.

Tip – when buying a coolant/antifreeze tester, make sure you get one that measures ethylene glycol. A lot of testers measure alcohol only, but this doesn’t tell you all you need to know about the level of protection your coolant is offering.

Mechanic is checking the radiator antifreeze, car engine

Why Do I Need to Check My Car’s Coolant?

Coolant/antifreeze can often go unchecked for long periods. Sure, a mechanic will look at the level as part of an annual service, but it’s not changed regularly like oil.

Of course, this is usually a good thing. If your car is topped up with premium coolant/antifreeze like Prestone, protection is guaranteed for a minimum of 10 years, which can save you a lot of time and money in the long term.

But if you aren’t sure when the coolant/antifreeze was last changed in your car, or you’ve recently bought a new used car, it’s important to test it to make sure the engine is protected.

When coolant/antifreeze is past its best, it no longer offers the same protection against extreme temperatures and corrosion. So if you don’t replace it, your engine is at risk from freezing and wear and tear, which could lead to costly repairs due to the damage.

What Should I Do if There’s a Problem with the Coolant/Antifreeze?

If something isn’t right with your car’s coolant/antifreeze, there are a few things to try. Here are a selection of pointers to help you troubleshoot different problems.

My coolant/antifreeze level is down on the reservoir 

If the level of coolant in the system is down, there may be a small leak that will need fixing.

To check for this, top up the system and check the level every day. We’d recommend taking a photo so you can keep track.

Has the level dropped? There’s more than likely a leak which you should repair as early as possible to avoid bigger problems.

Pouring coolant

My coolant/antifreeze is dirty but is still offering good freeze protection

Have you spotted dirt and particles in the coolant while testing it? This could be a sign that the cooling system is in poor condition and needs flushing to remove dirt and deposits.

Over time, small particles of debris can build up in the channels of the cooling system, where they can contribute to increased corrosion and wear. That’s why you should always flush the cooling system before adding fresh coolant/antifreeze.

Using a product like Prestone Cooling System Flush is a great way to remove scale, deposits and contaminants from the system in between batches of coolant/antifreeze. The product does a better job at clearing dirt and sludge than water alone, so you can be confident that you’re adding fresh coolant/antifreeze to a completely clean and clear system.

My coolant/antifreeze isn’t offering good temperature protection 

Temperature protection is vital for ensuring long-term engine health, so if your coolant isn’t protecting against extreme heat and freezing, it’s time to change it.

A premium coolant/antifreeze like Prestone offers temperature protection from -37°C to +129°C. That gives you the peace of mind that your engine is protected in all conditions, and at all times of the year.

Testing your coolant/antifreeze is a job worth doing throughout the year to ensure maximum protection for your car’s engine. For more help and advice, visit the Prestone blog or check out our full product range.

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