Rad/ cooling system not pressurizing ???

ok i dont get it since my re-build 1700km ago ive had no problems, all of a sudden i notice my rad has no pressure in it, the car still has a good nice cool temp at all times but no pressure, and the rad fluid under the cap looks to have a white foam in it like "fine soap suds " i dont get it , i have no leaks coming out the bottom, no white smoke.... no coolan in oil, no oil in coolant


what the hell is causing this ? my rad cap seems to look ok, its about a year old maybe a bit more, what do u guys think ?

i remember the first time i had this problem like a year ago it was the rad cap, but that one was noticable it was all deteriorated this one looks to be ok

any ideas guys???

Try warming it up enough to open thermostat then turn it off and see if you hear any hissing. I would focus on the heater hose on passenger side and on cap. If you don't see any then I would lean towards the cap.