CRXdan

Setup
Mishimoto half rad
Mishimoto slim fan
Mishimoto 16 psi cap
New OEM gasket
resurfaced head
new water pump
no coolant leaks

After a 20 min drive on the highway, I will pull in and shut off the car. I can hear a hissing coming from the rad cap area, and the top of my radiator has water spots all over it. If I slightly push on the rad cap the hissing goes away. There is alot of pressure within the rad hoses too. In the morning, when I go to drive to work, I have to add some coolant, nearly 1/2 litre. There is NOTHING coming out of the overflow. The car does not over heat or anything, and has seen numerous passes at the track and on the highway.
Faulty rad cap?
How much coolant system pressure is too much? Should I worry only of the hoses are swelling?
Would a pinhole leak somewhere introduce air pockets into the system causing the hoses to pressurize excessivley?

nsxmatt

Replace the cap first. No matter the setup you should not see that much of a rise in the cooling system pressure. If you do compression is going in the cooling system.

90sedan

Definitely start by replacing the radiator cap.

CRXdan

ok doesn anyone know if the niple on the black pipe feeding into the water pump needs to be ran somewhere. I am thinking this is some sort of pressure relief for the water pump. Right now I have it plugged.

90sedan

It's a bypass hose, it should be connected to the eacv.

yakuza

I got the same setup as you and so far been running perefect 150 miles plus, no loss of any coolant and my resv is empty.

When filling the coolant, did you unscrew the the screw at the back where the temp sensor goes next to it? You need to open that when topping the coolant until it comes out of there and then screw it back on. This ensures there are no air pockets in your coolant setup.