Skip the auto shop - Our mechanics make house calls

The Best Tool to Find Coolant Leaks

The Best Tool to Find Coolant Leaks

Arguably one of the most time consuming mechanical issues for a mechanic to properly diagnose is an overheating situation. Due to the fact that there are so many individual components, part failures, and symptoms that lead to overheating, many mechanics find it difficult and extremely frustrating to:

  • Find the source of the overheating problem
  • Determine if there are leaks in the coolant system
  • Locate the precise part or component that is faulty

However, there is a great tool and process that some of the most experienced ASE certified mechanics utilize to quickly diagnose overheating issues and detect coolant leaks which, when used properly, can save time and decrease your downtime on repairs. This tool is a coolant pressure tester.

The Best Tool to Find Coolant Leaks - coolant pressure tester
Image: Mac Tools

What is a coolant pressure tester?

A coolant pressure tester is a tool that most ASE service stations and independent certified mechanics use to diagnose a coolant leak. The tool itself is similar in many ways to a bicycle pump, with a pneumatic hose attached to a special adapter that is hand pumped after you attach the correct adapter fitting to the vehicle’s radiator. Once you secure the attachment to the radiator, you simply pump the pressure handle until the gauge reads about 15 psi and watch and listen for leaks to appear within the coolant system.

The tool itself is simple to use. However, the best mechanics know how to use the tool correctly to diagnose leaks in the entire coolant system. Since coolant leaks contributes to more than 80% of most overheating situations, using the coolant pressure tester correctly can expedite the search for most overheating problems.

How to use the coolant pressure tester effectively

When a customer contacts a mechanic about their car overheating, what’s the first thing that pops into their mind? Most ASE certified mechanics, instantly remember that faulty thermostats, broken water pumps or low coolant levels or coolant leaks are the main causes of the overheating situation. They also tend to remember from their training that one of the first things they should do when diagnosing a problem is to eliminate some of the potential causes through simple tests. When it comes to finding coolant leaks, this is best completed by using the coolant pressure tester correctly.

Here is how to do it right:

  1. Let the engine cool down for about an hour
  2. Remove the radiator cap
  3. Attach the correct adapter to the radiator
  4. Attach the coolant pressure tester
  5. Pump the coolant pressure tester slowly until you approach 15 psi on the gauge
  6. Once the gauge has reached that 15 psi level, make sure to do the following:
    • LISTEN for any air leaking from any fittings, hoses or the radiator itself.
    • WATCH for any leaking fluid coming from welds in the radiator, hose fittings or bends in coolant lines.
    • OBSERVE the pressure gauge. If you don’t hear anything or see fluid leaking onto the ground; leave the gauge attached for about 20 minutes. If the pressure does not fall more than 1 to 2 points, there is no coolant leak and you can move onto another potential cause of the overheating situation.

Having the flexibility to easily find a coolant leak is much easier when you use a coolant pressure tester; and use it correctly.

If you’re a certified mechanic and you’re interested in working with YourMechanic, submit an online application for an opportunity to become a mobile mechanic.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

How to Get Chevrolet Dealership Certified
Chevrolet car dealerships offer automotive technician jobs to mechanics who are certified through the many training programs available.
P0523 OBD-II Trouble Code: Engine Oil Pressure Sensor/Switch High Voltage
P0523 trouble code means there is an issue with the engine oil pressure sensor often due to faulty wire connection or wrong engine oil.
How to Replace the Rear Hub Bearing on a Ford Explorer
Wheel bearings allow the car's wheels to give you a smooth ride. A howling or grinding noise is a sign that your hub bearing should be replaced.

Related questions

Q: Leak under the back door on passenger side - 1986 Buick Electra Park Avenue 3.8 L V6

Hello. The fuel and the fluids need to be changed first before you can start the engine. Once it can be started, you would be able to see if there are any other issues with the car. Being that it...

Q: Truck overheating and clanking. What do I need to do to fix this?

The clanking sound you heard was most likely caused by the engine overheating to the point where it would no longer run. Once the engine gets so hot the fuel ignites in the engine before it’s supposed to and can...

Q: How do I know that my OBD system is working right?

The OBD system on your vehicle is a self-monitoring system. The Powertrain Control Module monitors and controls all of the systems and functions that regulate fuel, ignition, emissions, and engine cooling as well as having some minor control over air...