Cheap DIY Honda Coolant System Pressure Check

Have you needed to find a coolant leak, but you could never locate the exact location because of all the steam. You could go buy a Radiator pressure testing kit for $120 or even rent one. If those options are not appealing, you may have the tools you need already available to you.

What you need:
Compressor and Tire Valve. What is a nice feature about this compressor is it has a setting for max air pressure. The compressor will cut off when the set pressure is achieved. I set mine to the max pressure of the radiator cap.
(I took the schrader valve out of the valve stem, to allow for pressure to be bled off)
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Tire Valve comparison with radiator hole:
As you can see the tire valve fits perfectly against the radiator opening to create an air tight fit.
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FIrst make sure your engine and coolant are cold. You do not want to preform this test while the coolant is hot, or you will risk getting badly burned. To get the best results, you will want to top off your coolant so there is a limited amount of air in the system. Once you’ve filled up the radiator, you can put the tire valve in place. You will need to hold it there yourself, or have an assistant hold it while you look for the leak. To add pressure, you only need to turn on the compressor for less than a second. You don’t want to pressurize the system more than your radiator cap suggests. For Hondas its around 16 PSI.

Tire Valve in the radiator Hole:
Be careful at this stage, you can press the tire valve too far into the radiator, loosing your seal and pressure.
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Hose leak:
When the engine was heated up, I couldn’t pin point where the leak was coming from, because nothing but steam was pouring out. With the engine cold, a steady stream of water could be seen pouring out from the leak, while the system was under pressure.
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Relieving Pressure:
Once the leak has been located, you can either let the leak bleed off the pressure in the system, or you can relieve the pressure at the valve. Be careful at this time. I used a rag wrapped around the tire valve going into the radiator, to prevent coolant from spraying up. If the pressure is released slowly, just the air gets bled off from the system. If you release the pressure quickly, coolant will mix in and you will spray coolant everywhere. This is especially bad if you didn’t follow the above warning to do the pressure check when the system was cool. You can be badly burned at this step if the coolant is hot and you relieve the pressure too quickly.

I am not a mechanic. I’m just a fellow JDMU member who tried to save money where I can by fixing my car when I can. If you feel this is more than you can manage please do not attempt this. There is a serious possibility of being badly burned or other bodily harm. If you choose to attempt this fix, I am not liable for any injuries to you or damage to your car.


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