Why is my car going through coolant so fast?

(Last Updated On: July 12, 2023)

The coolant level is just as important as the oil level. To understand why your car is going through coolant so fast, it is essential to know that unless there is a leak, it will probably be a head gasket problem causing the coolant loss. When a head gasket fails, the coolant reaches the cylinder and will burn during the combustion cycle; cars burning coolant overheat and smoke quite alot.

There are many places in an engine bay to look for coolant loss, so before you get too disheartened and think the head gaskets gone, look at the areas for coolant loss below. It may not be the places you’ve already looked at causing the leak. On a positive note, not all of them come with a hefty repair price tag.

Where to look for Leaking coolant

  • Leaking radiatorThe radiator core tubes and fins can become damaged from debris in the road. Also, the end tanks can corrode on older vehicles; the usual place to look for coolant leaks in a radiator is along the bottom of the radiator casing; you can sometimes see the coolant leaking or spot the damp patches on the end tanks. It’s rare to see a leaking radiator from the mid-top of the radiator end tanks. Leaks from the core’s center are usually evident and easy to spot.
  • Coolant bottle – Cracks in the underside of the bottles where the pipes connect to the bottle are pretty standard. Sometimes the hairline cracks can be a little difficult to spot by eye without removing the bottle, but the marks left behind where the coolant has been dripping make it pretty obvious.
  • Heater system – The car’s heater system pipework runs around the engine bay to the dashboard; the heater matrix can fail and leak the coolant that runs through it. Occasionally this can be spotted by either smoke coming from behind the dash or traces of coolant in the footwell.
  • Water pump – Water pumps are separate items to the engine that are usually changed when the timing/cam belt is changed. However, when it isn’t, water pumps typically go wrong; with age, the seal between the engine block and the water pump deteriorates, so the pump leaks. You would never try to reseal the water pump if the internals are causing a problem; you would only replace it.
  • Water hoses – Most silicone or rubber hoses around the engine bay carry coolant to and from components. The hoses can split or become weak over time; replacing hoses is very straightforward, and they’re usually purchased as a direct replacement from the car dealership. Even the clamps that secure the hoses corrode and snap, so you may get leaks that just require a new clamp to resecure and seal the hose.
  • Overfilling the coolant system – Certain coolant systems have overflow pipes that release excess coolant if filled. Although, this won’t be a constant leak only when topping up and overfilling the coolant.
  • Broken coolant cap – The cap for the coolant bottle is a pressure cap; these can split or break, meaning the water content in the coolant mixture evaporates. Although when this kind of thing happens, it’s not a fast process, it can be noticeable if regularly checking the coolant level.

What if there is no leak?

The unfortunate thing is that if there is no evidence of coolant leaking, but your car is losing coolant, there is only one reason for it disappearing: it is being burnt inside the engine. The problem is that it means the head gasket has probably failed. The head gasket keeps the coolant flowing through the engine waterways and seals the motor, so it cannot enter the cylinder, and vice-versa, it stops oil from entering the coolant system.

There are other indicators that the head gasket the most common is loss of coolant, but other indicators to look out for are:

There are special snooping tools and liquid solutions that mechanics use to check for a blown head gasket without the need to strip the engine down to check. If you suspect your head gasket has failed or is failing, have your mechanic inspect your vehicle asap.

How much coolant loss is normal?

Although a sealed system is under pressure, due to the high heat temperatures of coolant, it is normal for some water content in the coolant to evaporate. This happens at a prolonged rate, so expect to lose no more than an ounce or two of coolant over 12 months. As a high-mileage driver, you can expect to lose a little more than this, but it should never be noticeable. If you find yourself topping up the coolant level regularly, it shows you have a problem, such as a leak.

How often should you check your coolant level?

The coolant level should be checked regularly, as it is even easier to check than the oil level; it is wise to glance at the coolant tank every month when performing other basic maintenance checks.

There is a minimum and maximum level on the side of the coolant tank; if the coolant starts to fall below the low marker, top up with a 50/50 mix of coolant and water. You can check the strength level of the coolant and adjust accordingly if you have a coolant strength tester or coolant test strips. In an emergency, you can top up the coolant with just water, but again the strength will need to be checked and the proper coolant added as soon as possible.

Final thoughts on why is my car going through coolant so fast?

If your vehicle is going through coolant so fast, the first call of action is to check for a leak. If no leak can be found, then, unfortunately, it will more than likely be a head gasket-related problem, and the engine is burning the coolant away. Most areas where the car could leak coolant are inexpensive to repair; however, if the problem is the head gasket, it’s not a cheap fix.

My name is Tom although my friends call me Tommy. Messing around with cars and bikes has always been a hobby of mine even from a young age. So I made it my day job 17 years ago. I am a fully qualified mechanic as you would expect. I've worked in all different areas of the motor trade, valeting, panel beating, engine repairs, I'm sure you get the idea. I enjoy sharing my wealth of knowledge and experience with others, which is the reason I spend a lot of time here writing for this website.

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