so yea like the title states my cooling system seems to be under alittle to much pressure.....So about two weeks ago my plastic tank on my oem radiator fractured thus making me invest in a mishimoto unit…..well I did the install with no problems bled the system and took it for a test drive when I got back to the shop and noticed coolant under the front spoiler I got my pressure tester to pressureize the system and well determined that the drain plug was not sealed (ended up being the o ring was seated funny on the drain welds) any way…I fixed the problem and let the fan cycle and in about 4 or 5 minutes idling the upper hose became rock hard, but seemed to drop slightly after every fan cycle. So I ate lunch and reinstalled the pressure tester again and started the car after I let it cool down and the pressure started climbing rather fast reaching about 5 psi in 2-3 mins I think it seemed to rase alittle fast for confort and after about 10 minutes it hit 13 psi before I shut her down. There was no movement either from the needle when I would crack the throttle (thinking it’s a slight head gasket leak) but I have been kind of busy lately and am stuck wondering if the f20c is just a pain to burp fully or I have a small amount of combustion leaking in to the cooling system….so now im interested in anyone’s experience with pressure in the cooling system or problems burping the system…or any head gasket problems ( the car is a 55k 2001 ap1 with a mishi rad, header back exhaust and k&n filter . basically any help or ideas would be greatly appreciated, Thanks!

 

I fail to see the problem with the stated pressure from your test. The OEM cap is set to lift at 1.1 kg/cm2.That is around 15-16 psi.

 

thanks for the post....the test was heading up toward 15 psi when i shut the car off but i guess i was worried about the hard upper hose at the time....what does the pressure feel like on the upper hose under normal opperation condition? does it get fairlly firm? tthanks

 

Yes.The hose will feel firm once the T/stat opens up. As long as your radiator cap is operating correctly within spec range it will relieve into the expansion reservoir and maintain the design operating pressure on the cooling system. If your test was started with the engine cold then once you ran it long enough that the fan cycled through a few times,the existing cap on your radiator should have relieved some fluid into the reservoir.That's why this reservoir has two level marks.One for 'cold' and one for engine warm or 'hot'. The reservoir should rise and fall between uses if things are working right.Once again ,just insure that the radiator cap you have in use is of the proper pressure range.