Re:Cooling system testing - Have I been doing it wrong?

Ran across this in service info on my '13 Sentra:



I had to go back and read the testing procedure a couple times. Nissan wants me to be pressurizing these systems to 23 PSI for leak testing? :blink: When the cap is rated for 14 PSI? This sounds like the fast track to a popped radiator.

My standard practice has been to pressurize a cooling system to the cap rated value. Maybe a pound or two more, if I really want to stress the system. I figure, if the cap is rated at ___ PSI, then that's what the system operates at. Assuming a good working cap, anyway.

Maybe I'm just being a wuss? :silly: Does everyone else dial up their pressure testers as Nissan suggests? Have I been doing it wrong the whole time?

Never seen that SI myself. I do the same as you a couple lbs over cap pressure

Same here if it holds cap pressure + 2 psi cold I'm happy.
Some BMW are running 200kpa caps --- 2 bar a bit over 28psi !!!!!

Ha, I've seen that and never do it. First time I saw that was on an armada and I just figured that if the cap is working, it won't ever see that pressure, so no need to get it up that high.

On a similar note, I've been using a vacuum fill tool for a bit now, and was wondering the same on the vacuum side. It's nice to pull vacuum and let it hold to test for leaks before filling to verify the repair. The gauge goes up to 30" I believe and the green dashes start at 20 or 25" indicating a no leak zone. I am always weary to pull too much though. Would you stick to that guideline with vacuum too or not be as concerned?



Nissan Tech

A new cooling system could probably handle at least 2X cap pressure. The 10+ year old stuff I see no way am I going over cap pressure.

Tutti57 wrote: On a similar note, I've been using a vacuum fill tool for a bit now, and was wondering the same on the vacuum side. It's nice to pull vacuum and let it hold to test for leaks before filling to verify the repair. The gauge goes up to 30" I believe and the green dashes start at 20 or 25" indicating a no leak zone. I am always weary to pull too much though. Would you stick to that guideline with vacuum too or not be as concerned?

Hard 30" vacuum is only 14.x psi below atmospheric, so that's the absolute max pressure difference pulling a vacuum could create. And it'd take a real vacuum pump to hit that. A venturi coolant filler probably wouldn't pull lower than mid 20s, which is around 12 psi.

I've used mine a couple of times but never had much faith in vaccuum fill I always initially fill with a couple of hoses loose.

Ok, good to know about the max vacuum. I love using mine. Some of these things are hard to get air out of.



Nissan Tech

Thanks for the replies, everyone.

The gauge goes up to 30" I believe and the green dashes start at 20 or 25" indicating a no leak zone. I am always weary to pull too much though. Would you stick to that guideline with vacuum too or not be as concerned?

I like the 25" value for leak testing/filling. Sometimes I'll go 26-27", solely because of the way my gauge is made, and it's easier to visually see leakage by making the needle go past the 25" mark.

I've also had cases where I was vacuuming a leaking system, and it struggled to achieve 25". Being able to go past 25" gives me more confidence in the system.

I've HEARD other techs say that they've damaged intake gaskets on older GM Vortec engines and the like. Supposedly the suction causes the gasket to suck in and start leaking into the crankcase. Take that for what you will. I never hesitate to vacuum fill these engines, and haven't caused any damage (that I know of).