heating but no hot water after pump replacement??

[cjb1971]

Fitted a new central heating pump on friday as the customers had burned out.Got call today saying heating was fine but no hot water.
System is old oil boiler,with pump besides it on flow-simple on/off/timer programe-no seperate timer for heating/hotwater.
hot water tank has thermostat linked to an actuator valve-so when it reaches temp-water is diverted.
Took the head off the actuator,the valve is very coroded but stuck in the on position-actuator head doesnt wrk-prob burned out.
the flow and return pipes at boiler are hot-the flow and return at cylinder are cold-had suspected trapped air but non of the rads have a drain off on them to try and get the air out of system.

Pump was changed using the isolation valves so minimum air would of got into system.
Had to leave job after this quick look-any body got any ideas besides trapped air? as it will be a pain to drain down if it is the cause,they said was working fine b4 so kinda rules out the valve coroded up-unless it aint been working for ages of course!
The have an emrsiopn heater in the tank so they dont want it sorting if its gona cost £££`s
Found some good advice on this site since starting my servicing/repair job a few months ago-still a lot to learn but seems to be getting easier untill jobs like this crop up!
Any help would be apreciated

 

[sparkyspike]

I suspect the actuator, although without seeing the installation, hard to tell!

 

[Slugbabydotcom]

Took the head off the actuator,the valve is very coroded but stuck in the on position-actuator head doesnt wrk-prob burned out.

Have you answered your own question here?

If not I take it that you bled air from any manual vent between the 3way valve and the cylinder?

 

[cjb1971]

Its only a 2 way valve-about 12 inches from cylinder and no vents on system at all!

 

[ChrisR]

Might have to "crack" a nut then to let air out. Try the one on the valve first, cos the cylinder ones can be weak connections, so its easy to get a leak.