So I changed my radiator with a new one, I dont think I have managed to 100% get rid of all the air yet as it took a long time for thermostat to open up because my inside heating was on MAX with A/C off. So i'm going to attempt to burp and bleed it with the funnel method again today. But I thought i would try out a pressure tester that I purchased a while back. I connected it all up and pumped the hand pump to pressurize to 15psi (i think it's supposed to be 16 psi, but i thought i'd play it safe) Actually it was on the right side of the 15 mark and then about 15minutes later i checked it, it was on the left side of the 15 mark, then i left it on there for another 35 minutes meaning a total of 50 minutes and it was still around the 15 mark on the left side of the mark. I would say that in the 50minutes it probably lost 0.8 psi and 90% of this drop happened in the first 15minutes, the remaining time it was rather steady. I have attached a picture illustration below of before and after.

I cannot see any visible leaks on the radiator, the hoses or the water pump. Any advice? Is the pressure supposed to remain spot on the entire time? Could air in the system cause this?

 

Potentially a temperature change could be enough to move the needle that small amount. I wouldn't worry about it. The fill funnel is best.

That said, the Next time you run it, turn the HEAT on HOT and (manually turn the fan speed down if hot out).

PS several short runs where the block comes up to temperature is best.. its the cool down cycle that fills the block and empties the reservoir.

 

I've found pressure testers themselves leak slowly that's probably what is happening to you. If there is any air remaining it will work itself out from the heat/cool cycle of the reservoir.

 

Can temperature change even though the car was sitting all night and I did this pressure test in the morning on a cold engine? Temperature outside was cool as it was done early in the morning. Why is it that when I last did the funnel bleeding that when I rev up the car then bubbles come up? I will try bleeding again today and run at 2k rpm and turn inside heat off maybe. I think my biggest worry and paranoia is if I have head gasket issue or anything.

that's what I thought but then later when I disconnected the hand pump at the quick release connection that connects to the radiator cap, I pumped up just the pump to see how well the pump itself holds pressure in it's hose. The pump didn't lose any pressure at all.