In the UK, the B7001 grey has thermo syphon cooling with no pump. It doesn't work. The official B7100 does have a pump and thermostat and I guess does work. I spent hours and hours, and a lot of money, checking the coolant for CO2 contamination, having the rad cleaned, cleaning it again myself, checking the timing, etc. etc. All was OK. I'm told you can fit a s/h B7100 timing cover and new water pump and alternator. Probably easiest but costs most. In my case I fitted a Davies Craig 12v EBP pump, 5 ohm rheostat from RS components and a Quinton Hazell thermostat QTH126K. The whole lot was connected using 2 x Kubota hoses 15371-72850 and standard plumbing copper pipe + fittings - 35mm which fits the hoses +22mm and 15mm. You'll need to solder here and there. Now it works perfectly at 80 deg C. all the time.
Meopham_Trader
May 2008