Rad pressure tested.......pressure did not drop

However, after leaving the engine running for a while, then revving, I noticed a small jet of water shoot out from in between the fan blades. Did another pressure test, and still no drop. Weird.
Drove to Brackley, temp started rising as I joined A43, then had to wait at roundabout, and temp went into the red. As I pulled away, coolant warning came on, so stopped in layby, cooled down, topped up and continued to Brackley...no probs.
Pressure tested again ....no drop

......but again, noticed another small jet through fan.
Came home today.....ran ok till Wycombe, then temp up slightly, till I stopped at traffic lights, and temp went into red, but no coolant warning.
Did the last three miles with clenched buttocks, but got home ok. This time, under the bonnet was well wet, so have put a new rad in.

Just hope nothing else is broke as temp went so high (the fans did cut in)
Could water and anti freeze on the aux belt make it slip and the new water pump not work

? Why did the temp go into the red, with fans working
