in my 2000 chevy venture 3.4 LS my water in my radiator pushes up instead of goes down and builds pressure on the over flow. What causes that? Would a head gasket or intake cause that?
Likely a blocked radiator or a leaking radiator cap.
When's the last time you flushed the radiator? You likely have Dex-Cool in there (is your coolant red?), this coolant is more prone to making deposits and needs to be flushed more often than GM would like to admit. I have an '04 Montana, and I had the same thing happen this time last year. Water pump was leaking, so I changed it and took the opportunity to flush the entire cooling system (I had just bought the van off a friend's old Mom). The old coolant was cruddy as heck, flushed it with plenty of water, put new coolant in there, no more boiling over since.
A new radiator cap is about $10.