Originally Posted by stefenboy

I would always do the pump when doing the belt.

My timing belt was replaced with my waterpump. I tuned the car on 91oct and e85 now im doing head gasket and arp studs because coolant is being pushed to the overflow tank. Overnight the cooling system is still pressurized and when i open the cap i can hear the air pressure that is in the cooling system hissing out. Coolant from the overflow tank is never cycling back into the cooling system because there is constant pressure in the system. I believe that is caused by the slightly blown head gasket. I believe what others stated about combustion gases going to the cooling system to push the coolant to the overflow is true. Because my coolant is never going back to the system im going to replace the head gasket and upgrade to arp head studs. My engine temp never went higher than it should. I never had this issue as my coolant was always at the lower of the bottle until this has happened to me. No oil in coolant, no coolant in oil. Car drives normal and engine temps are normal. Pressure test the cooling system and its good as well. Its weird. Hope the head gasket is the cause.

Originally Posted by Lombardi23

going to be doing belt soon should i do the pump?

Originally Posted by Lombardi23

OEM pump?