Woracester Bosch loosing pressure

[Tanner1]

My Worcester Bosch boiler keeps loosing pressure
It still works but pressure keeps dropping
An engineer pumped up pressure cylinder and emptied of water but pressure still dropping

Is the pressure relief valve faulty and causing water to drain from overfill pipe???

 

[45yearsagasman]

There sould be no water to "empty" from the exp vessel. Only water is on the system side of diaphragm. What pressure is indicated on the gauge?

 

[Tanner1]

Hello Pete
Yes that's what he said he emptied.
He repumped but still pressure went down

Pressure drops to 0 from 1.5

Is been doing this for a while now, I can't see the overflow pipe from the outside as it is a flat that I rent.