New water pump

[yowiie]

I just had a water pump replaced in VY Calais LS1, just took a trip up and back to Bris, I had to continually fill radiator with water, there are no visible leaks, at one stage water in reservoir was boiling
temp gauge never moved , but low coolant alarm kept coming on.
I got back home after 400k trip after repeated stops to fill reservoir, I pulled into the driveway and the need on temp gauge went straight to red.
I let car cool-down to a degree and refilled with motor going, yet to see the outcome
could it be a faulty cap. It never played up prior to new pump

 

[Fu Manchu]

Air coming out and faulty cap.

 

[yowiie]

Why would cap decide to **** it self after a new pump fitted

 

[bluehighway]

Check radiator for hairline crack around top hose neck ..also could be head gasket leak . If the old pump was leaking and the temp got high or it lost water replacing the pump may not have resolved the problems the first pump leaking caused. I would be surprised if it was the reserve coolant tank pressure cap at fault it is designed to leak pressure at a certain point. Given the long drive/high temps and top ups im thinking head gasket leak very possible fingers crossed its not.

 

[Fu Manchu]

In a pressurised system, eliminate one weak link and the next weakest steps up for a go.

 

[greenacc]

Why did water pump need to be replaced?
Replace the cap because it's easy and see what happens after that.