anyone know how much pressure there is supposed to be on the cooling sys cause my RX gets quite a bit of pressure build up in the upper radiator hose it doesnt blow the cap off or anything it just build up pressure then when i shut the car off it hisses air out the overflow for about ten seconds?

 

bad coolant seals in the block

 

yep.

 

Check to make sure you don't have air in the system, air bleed vavle for S4. Check to make sure raditor cap is up to spec, preasure test the system to see if there are any leaks. Also to check if it is indeed a bad coolant seal in the motor.. does is smoke? If you take off the raditor cap ( when cold) and turn on the enegine, does it giser out?