How to Find and Fix Coolant Leaks

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Spot coolant leaks and get them repaired quickly
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Coolant, or antifreeze, ensures your vehicle stays cool all year. Coolant leaks can cause an engine to overheat, leading to eventual engine failure. This is not only a costly problem but a dangerous one, too. In this guide, we’ll teach you how to find, identify, and fix coolant leaks with expert advice from automotive repair specialist Duston Maynes.

Coolant Leak Signs & Fixes

A coolant leak appears as a colorful residue or stain near the radiator cap, hoses, or water pump. Fixes can range from simple DIYs, like replacing the radiator or head gasket caps or using epoxy resin to seal minor cracks, to major engine overhauls that require a mechanic.

Section 1 of 5:

Signs of a Coolant Leak

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  1. If there’s a hole or crack in your radiator, hoses, or reservoir tank, look beneath your car for any colorful puddles. Coolant, or antifreeze , can leave behind a green, blue, pink, orange, or yellow puddle. Automotive repair specialist Duston Maynes recommends promptly bringing your vehicle to the shop for a leak, as it can be the beginning of something more severe.
    • It can help to leave a large piece of paper or cardboard beneath your vehicle overnight to catch the leak.
  2. A faulty water pump can cause coolant leaks, leading to an overheating engine. You may also hear a high-pitched squealing or whining noise from the friction of hot components rubbing against each other. [1]
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  3. When the engine temperature increases, you may notice a sweet smell coming from beneath the hood after shutting the vehicle off. This is the coolant “burning off” after use. [2]
  4. When the coolant levels drop too low, the engine cannot effectively cool down quickly, leading to overheating. On your vehicle’s dashboard, pay attention to the temperature gauge. In most vehicles, it will be a small gauge with C for “Cold” and H for “Hot.” Over time, the engine may release heavy steam and a sweet, burnt smell. [3]
    • Left unaddressed, it can cause serious damage and engine failure—putting yourself and other drivers at risk. [4]
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Section 2 of 5:

How to Find a Coolant Leak

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  1. You'll need to locate the leak first to determine how bad a coolant leak is. Inspect the bottom of the radiator and check the radiator itself, the hose, the drain valve, and the reservoir. Look for a slow drip from one of these places. Additionally, you can park your vehicle on top of cardboard and wait for the leak to drip. [5]
  2. Alternatively, you can detect an engine coolant leak by pressurizing the cooling system. Get a hand pump or compressed air , then remove the radiator cap. Plug the overflow valve, fill the system with air, and monitor the gauge for any pressure loss. [6] Pressure loss indicates there’s a leak.
  3. Start with a cool engine and remove the radiator cap. If your coolant level is at the maximum fill line, you may want to remove a small amount to make room for the UV dye. Add the dye to the radiator and top it off with water. Run the engine for 15 minutes so the dye can circulate through the system. Afterward, use a UV flashlight to inspect the engine. Leaks will show as a bright green or yellow stain. [7]
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Section 3 of 5:

How to Fix a Coolant Leak

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  1. Radiators are pressurized, so when a cap is loose, it can cause the coolant to escape. Allow your vehicle to cool down before locating the radiator cap on top of the radiator. Unscrew the cap with your hand. Look for signs of damage, cracks, or corrosion. Purchase a matching radiator cap and screw it on. [8]
    • Cost of Repair: A cap replacement can range between $13 to $40. [9]
  2. If you notice a crack in the radiator, its hoses, or the expansion tank, this can prevent the radiator from effectively cooling the engine. Inspect your radiator for any visible cracks, holes, or corrosion. Apply a bead of epoxy-resin resealer directly to the crack or hole. [10] This should only be a temporary measure, according to Maynes. Relying on a sealant can cause a clog in the process, and it’s best to refer to a professional.
    • Cost of Repair: A leaking radiator can range between $700 and $1,000, depending on the repair, vehicle make and model, and the radiator type. [11]
  3. Water pumps circulate the coolant through the engine to prevent it from overheating. Locate the pump beneath the lower part of the engine, near the drive belts. Look for signs of cracks, holes, or corrosion. To fix a water pump, detach the negative battery line before removing the radiator cap and emptying the radiator of its liquids. Detach the radiator hoses, belts, and fan shroud using a wrench. Apply an industrial cleaning solution to the pump and apply a gasket sealant before replacing the water pump.
    • Cost of Repair: A repair or water pump replacement can range from $400 to $1,000. [12]
  4. Immediately turn your vehicle off in a safe location and avoid driving. Inspect the coolant levels under the vehicle's hood. On the side of the coolant reservoir, check that the coolant is between the “low” and “full” marks. Add more coolant to see if this helps. If not, seek the assistance of a professional to diagnose the problem. [13]
    • Cost of Repair: Engine-related issues can run anywhere from $100 to $8,000 depending on the issue and vehicle make and model. [14]
  5. Head gaskets help keep oil and coolant from mixing, but when there’s a leak, it can prevent your car from starting correctly. [15] To replace the gasket, clean the surface to remove any rust or debris in contact with the new heads. Carefully position the new head gasket and press down to fit it in. Install new bolts so you have a snug fit. [16]
    • Cost of Repair: A blown head gasket replacement can run between $1,000 to $2,000, depending on the complexity of the engine. [17]
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Section 4 of 5:

Is it safe to drive with a leak?

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  1. If you suspect your vehicle is leaking coolant, locate the leak first to determine its severity. If it’s a slow leak, drive to your local mechanic for an inspection. However, if it leaks too much, Maynes recommends towing your vehicle to avoid overheating the engine.
Section 5 of 5:

Preventative Maintenance

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  1. At some point, you’ll need to change your coolant. On average, most people opt for a simple refill. But, for older vehicles, the coolant should be drained or flushed every 2 to 3 years, or around 60,000 miles. Coolant can last up to 5 years, or 100,000 miles for modern vehicles. Refer to your vehicle’s owner manual for the manufacturer’s recommendation for coolant changes. [18]
    • Change your coolant when you notice a change in the color or constancy of the cool, a sweet, strong smell from the engine compartment, or if the engine temperature increases.
  2. To keep your vehicle in tip-top shape, look to the coolant levels every 3 to 6 months to see if it needs to be topped off or drained. Look at the overflow tank next to the radiator and ensure it reaches the fill line outside the reservoir. If it’s beneath the low line, use a funnel to add more coolant in. [19]
    • Coolant should be flushed when it’s brownish or colorless. Healthy coolant will be green, blue, yellow, or red.
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      References

      1. ↑ https://www.autozone.com/diy/engine/symptoms-of-a-bad-water-pump
      2. ↑ https://aamcominnesota.com/the-nose-knows-6-car-smells-to-watch-out-for/
      3. ↑ https://www.themechanicdoctor.com/dos-and-donts-overheating-cars/
      4. ↑ https://www.autozone.com/diy/antifreeze-coolant/what-causes-coolant-leaks
      5. ↑ https://www.themechanicdoctor.com/guidelines-to-identify-and-fix-car-radiator-leakage/
      6. ↑ https://heartautocare.com/how-to-find-an-engine-coolant-leak-without-a-pressure-tester/
      7. ↑ https://heartautocare.com/how-to-find-an-engine-coolant-leak-without-a-pressure-tester/
      8. ↑ https://repairpal.com/radiator-cap
      9. ↑ https://caradvise.com/car/services/radiator-cap/
      1. ↑ https://www.autozone.com/diy/radiator/cracked-radiator
      2. ↑ https://www.synchrony.com/blog/automotive/how-much-does-it-cost-to-repair-a-car-radiator.html
      3. ↑ https://www.jdpower.com/cars/shopping-guides/how-much-does-it-cost-to-replace-a-water-pump-on-a-car
      4. ↑ https://www.jiffylube.com/resource-center/what-to-do-when-car-overheats
      5. ↑ https://www.autozone.com/diy/engine/engine-replacement-cost
      6. ↑ https://www.firestonecompleteautocare.com/blog/maintenance/blown-head-gasket-causes/
      7. ↑ https://www.tvh.com/learning-hub/replacing-a-cylinder-head-gasket-when-it-needs-to-happen-and-how-to-do-it
      8. ↑ https://www.kseal.com/expert-advice/engine-problems/how-to-fix-a-blown-head-gasket/head-gasket-repair-cost
      9. ↑ https://www.autozone.com/diy/antifreeze-coolant/how-often-do-i-need-to-change-coolant
      10. ↑ https://www.tysonmotor.com/service-department/service-parts-information/how-to-check-coolant-levels/

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