problems with my surf overheating

[RICK ls27]

hi i'am new to this forum but have had a 2 gen ssrx 3lt ltd m reg for the last 4 years the truck is brilliant best car we;ve ever had .but when towing our twin axel caravan temp gauge goes up nearly into red when going up hill but drops when going down hill .changed thermostat about 18 month ago that seemed to help on a recent trip to scotland temp went into red so we pull up and noticed water coming out of expansion tank...changed water pump and removed aircon rad but just wondering if i've overlooked anthing really simple or could head be cracked...

[Koi]

blocked rad can do this (externally) my old 2.4 did it when under heavy load even on the flat. Just cruising it was fine, turned out a few off road trips and general crap in the fins had partially blocked it stopping good air flow through it.

[RICK ls27]

thank for the advice been reading a few post on here very good info going to change rad cap and do a rad flush as well as cleaning rad any advice on coolant been running on of the shelf normal stuff for diesls as anyone heard of a towing rad for surfs ???????/ any tips or advice really welcome love our truck and do'nt really want to part with her