Hi guys, new to this so please bear with me!

I have a 2000 B5 1.9 tdi which I use to commute to work and back daily (80 mile round trip).

Last week, roughly 25 miles into the journey the car suddenly felt 'lumpy' on the throttle for a couple of seconds and I noticed the temp gauge started to creep up until I pulled over and knocked the engine off. Lifted the bonnet and released the pressure from expansion tank and it started to bubble over violently and dumped a load of coolant out of the overflow. Replaced cap and started engine, temp returned to 90 and stayed there for remainder of journey.

Return journey all was good too until next morning same this happened around the same distance into drive. Bottom hose to radiator was cold to touch so so assumed thermostat was sticking or broken. Replaced with vw part and fine for a couple of days.

Had the same issue again today but this time after realising the pressure and continuing on journey I released the expansion tank cap and no water returning to the tank. Am I right in thinking this is a water pump failure/failing?

Cheers, Keir.