I replaced the rusty leaking pipe last year and noticed after that, that the temp gauge doesn't stay in place when in traffic. 9 months later, the engine is dead - head gasket problem.
When replacing this line, you had to remove the lower radiator hose. When refilling it with dex-cool, make sure that you let the air out of the system. There are two nipples on top of the engine - one close to lower hose and the other is after the thermostat. If not done, you probably would end up with bad head gasket later.
01 Venture