Pressure Test Cooling System

Hey Austin, you mentioned in a previous post to another question that the guy should get a cooling system pressure test to determine where his coolant leak might be in his car engine. Why would you need to do that if there is a leak, can’t you see it?

Shannon D.

Hi Shannon,

Great question, thanks for asking.  When there is an overheating engine problem with a car, the first thing I want to rule out is …is there a coolant leak somewhere.  Yes, some cases the leak is obvious to the naked eye, but many if not most cases the leak is not visible.

Pressure testing the cooling system is the first thing I want to do…find the leak and repair it and see if that solves the overheating problem.

The pressure test will also check for internal coolant leaks, like a crack inside the engine or a head gasket that has failed and is leaking coolant inside the engine. The test won’t tell me exactly what happened, but it will show a loss of pressure and if I can’t find an external leak (like a radiator hose) then I can start looking deeper inside the engine for the problem.

Basically a pressure tester is just a handheld air pump that attaches to the radiator or coolant overflow bottle and allows me to pump air into your cooling system which helps push out the coolant…through the leak so I can see it with my eyes.

If the pressure test holds pressure, then I can rule out a coolant leak and start looking for the source of the overheating else where.

I get so frustrated with mechanics who fail to do this SIMPLE and fast test.  Why?  Because people jump to conclusions to quickly.  “water pump is bad” ” yep, you MUST have a blown head gasket” etc, etc, and it might be just a leaking heater hose or radiator hose or something simple like that.  In many overheating cases it is a simple issue like a hose.

Soooooooo, that is why I recommend everyone pressure test the cooling system first in an overheating issue.  Now, if you open the radiator cap and the radiator is full and you have not been adding coolant, ok…you can skip the test and look elsewhere.

I made this video about overheating issues, you might find it helpful so watch it.