I've left it alone, now till Monday. I also think that you chasps have gone beyond the call of duty. I admit there's one thing I've overlooked. The receiver tank underneath. I've checked and replaced suspect ailines to it and renewed the bung and checked entry and stopper points for leaks. I haven't checked the tank itself.I haven't replumbed it from the valveblock to the rear nearside wheel arch, which I'll do. Now you've educated me to level one I can see that the system needing to be replenished as it is must be caused by a leak. I've shot some footage( I'm sure you know what a pump sounds like running and then stopping for a few seconds, though) and done the basic tests as per the gospel according to wammers. If all is as it should be with the doors open and stationary overnight and the problem only arises whilst the engine runs, I can see it must be something to do with the tank which gets isolated with the engine off.(does it?) For the pump to run 90% of the time there must be not only a leak but a mighty one, but only when the engine's running. Either that or it's being told to run by something that doesn't know what it's talking about. God knows how you've managed to stay with this thread as you have.(my patience hasn't arrived yet BTW) We bought our caravan from Reads in Blackburn where we go each year to get it serviced and to visit friends and relatives of the wife who's a Lancashire girl. We have relatives in Leyland. So, medication and supervised excursions permitting, there'll be a wee dram on offer at the venue of choice in Preston. Sorry, Grrrrrrrrrrrrr, I'll just send the money. A pint for wazzajnr and I think myfirstL322 must be in another wing here. I'll ask matron. Very best regards. P.