Shower pressure bounces when I try to change temperature

[jonnywhich]

Hi, I have a Mira Coda shower (so its just a general mixer shower, not electric or power shower). I'm finding two things, one is that it's started to make a feint but constant "groaning/buzzing" noise when the shower's on. Secondly, if I try to change temperature the pressure bounces up and down a bit for a couple of seconds before coming back to normal. I'm not having any problems with temperature, that seems fine. I was wondering if the mixer valve was in need of replacement, but then I'm not an expert so don't really know anything.
I did set the shower to cold only and the noise was still there, which makes me think it's probably not an issue with the boiler pump and is more likely to be the shower itself, but again, I'm no expert whatsoever.
Any ideas or advice would be greatly appreciated. Thanks in advance.

Jon

 

[spanner]

Sounds like a mixer valve blending issues - UNLESS you've a sealed or open vent type system and have booster pump added to boost your desire at the outlet??
If so ..
Could be again an unbalanced at controls at the time - depending on boost - what is boosted - if boosted?
If Balanced boost then I'd have thought its at the valve blender itself..??

 

[jonnywhich]

Sounds like a mixer valve blending issues - UNLESS you've a sealed or open vent type system and have booster pump added to boost your desire at the outlet??
If so ..
Could be again an unbalanced at controls at the time - depending on boost - what is boosted - if boosted?
If Balanced boost then I'd have thought its at the valve blender itself..??

Thanks for your reply. I'd bought replacement parts but when I took it all apart I found a large buildup of limescale at the filters, so I changed filters and flushed the remaining buildup from the pipes. It's like a new shower now, and still got the mixer as a spare for if I might need it one day.

 

[spanner]

BRILL...nice one.. Good to know it's working like new again..