Can you use a radiator pressure tester with the engine running?

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I was going to pressurize the system to 15psi and then run my engine to operating temp.

Is it a bad idea to do this? I'm thinking it might make a leak location I'm suspecting more obvious.
 
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Follow the directions that came with the pressure tester. Plastic tanked / aluminum radiators may be more susceptible to damage from too much induced pressure.
 
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Using the tester alone allows for inspecting the system without burning yourself on hot coolant or engine parts. It will also take the fan out of the equation, in terms of safety and blowing leaks away from their source.

The tester itself will create plenty of pressure. I also wouldn't be surprised if they aren't designed to withstand hot coolant.
 
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I was going to pressurize the system to 15psi and then run my engine to operating temp.

Is it a bad idea to do this? I'm thinking it might make a leak location I'm suspecting more obvious.
What happens when then pressure builds up from the heat?
 

Puhdantic

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I asked about this because I recall reading it in my auto book.

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I think the distinction I missed is that the engine is warmed up , but not running.

My coolant temp was 160F and the engine was off. With it pressurized in this state, I was able to see coolant leaking from spots I suspected. Once the temp had dropped much lower and I re-pressurized the system, I could not see the leaks at the same spot.

Increasing the pressure to 16psi with the engine cooled down I was able to see a clear leak from a crack in a different spot I suspected.

So I think the idea the book is saying is to connect the pressure tester, bring the car to a warmer temp, turn it off, then pressurize it and check for leaks.
 
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ZeeOSix

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I asked about this because I recall reading it in my auto book.

View attachment 109287

I think the distinction I missed is that the engine is warmed up , but not running.

My coolant temp was 160F and the engine was off. With it pressurized in this state, I was able to see coolant leaking from spots I suspected. Once the temp had dropped much lower and I re-pressurized the system, I could not see the leaks at the same spot.

Increasing the pressure to 16psi with the engine cooled down I was able to see a clear leak from a crack in a different spot I suspected.

So I think the idea the book is saying is to connect the pressure tester, bring the car to a warmer temp, turn it off, then pressurize it and check for leaks.
You could bring the engine up to full operating temperature, shut it off and then slowly open the radiator cap very slowly with a big towel around it (so it doesn't spray) to slowly release all the pressure. Once the pressure is relived, then remover the radiator cap, attached the pressure tester and pressurize the system. That's what the article is basically saying.
 
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As long as it would fit, I think I would remove the radiator cap, and install the tester, then warm up the engine. When it hit operating temp check to see what the pressure reads. Then, check everywhere where a leak might happen. At that point, I'd try to decide if I needed to replace the cap or not. As the system ages especially with a plastic radiator, I might drop the cap pressure a bit.,,
 
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