"Roger Mills" wrote in message
...

I reckon that the lining of the pressure hose is de-laminating, and
cutting off the flow. Then the by-pass opens and releases the pressure,
the pressure hose recovers for a bit and lets through another pulse - and
then the whole thing repeats on a once per 4 second cycle.



OK ... the pressure hose is in s**t order, outer covering all peeling off,
so inner could be crap.
It was going to be changed this year.

I don't have a spare hose to try though ... so that limits my next step