How To Find a Coolant Leak

Coolant leakIs your car engine overheating? Are you losing coolant on a regular basis and having to constantly refill the radiator or the overflow reservoir?  First thing you need to do is get a cooling system pressure test to help you locate the coolant leak…unless it is obvious with the naked eye.

A cooling system pressure tester is basically a small hand held air pump like you would use on a bicycle tire. One end of the pressure tester has an adapter you screw on to the radiator neck or the top of the overflow bottle if your vehicle does not have the old style radiator cap.

With the engine off, radiator full of water and the tester attached to the cooling system slowly pump air into the system and look around the engine area for the coolant to leak out. There should be a gauge on the tester with PSI numbers. Look on your radiator cap, or a label under your hood or on the reservoir bottle to find the cooling system pressure of your vehicle.  Most vehicles are between 12-14 PSI, so do not add much more air pressure to the system than that or you could cause a leak :)

Sometimes the leak can take a few minutes to show up, so be patient and keep looking around the top, side and under neath of the engine for signs of water/coolant leaking out.  Also keep an eye on the tester pressure gauge and see if it is holding pressure or the gauge pressure is slowly dropping.  You might have an internal coolant leak (like from a bad head gasket) if the pressure gauge drops but you do not find any external leaks.

You can read my posting on head gasket leaks and how you might be able to repair it using a simple and cheap over the counter sealer.

Now before you ask, I would not personally use a coolant leak sealer but would rather repair the leak properly. Yes, if you have an older style all metal radiator and the radiator itself is leaking you can try using Bars Leak, but for anything else…it just won’t work.

Below is a video of someone using a cooling system pressure tester to help locate a coolant leak, which just about any mechanic can do for you or you can rent the tester at your local auto parts store and do it yourself.

This is my engine overheating video that also might be very helpful to you when diagnosing running hot issues.

Austin C. Davis

Posted in: Coolant Leak

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."