Vaillant Turbomax noise

[Scott_D]

Went to do a gas safety check on a Turbomax today
It’s fine in CH
Makes this groaning noise in HW if the temp dial is above half way.

Diverter?
Doesn’t seem to have a bypass

 

[AMGasServices]

It’s fine in heating and HW if the temp dial is below half.
Only happens if the HW temp is turned up

Turn the temperature up to max use the tip of your screwdriver (put it on each component in the area you’re hearing the noise) and put the handle of the screwdriver at your ear. Use it as a stethoscope.

 

[Ollieg]

burner pressure is too high. Or a restriction on the plate causing poor circulation.

 

[Ollieg]

burner pressure is too high. Or a restriction on the plate causing poor circulation.

 

[Ollieg]

the bypass comes off under the diverter and runs to the back of the boiler and then round.

 

[MARTIN LISTER]

I had exactly the same problem with a TURBOMAX PLUS 824 E. It made the noise only when the burn modulated up to full. Could not trace it to any particular component because the whole boiler vibrated. Fitted a new primary heat exchanger and solved it. Fairly easy to fit. No visible fault on old heat exchanger.