Hi there
I own a 1997 1.9TD Fiat Ducato Motorhome. I had some problems with overheating so I decided to completely flush the coolant system and replaced the radiator as quite a few of the fins were damaged.

Now when driving slow, 1st, 2nd & 3rd gears even stopping and starting in traffic queues it stays at a constant 90 degrees, dead on half way. With the fan switching on and off as necessary.

However when I drive at speed on motorways, dual carriageways or up uphills, it rises right up to 3/4 on the temp gauge not on the red but just short of it.

All the other vehicles I've owned and drove have behaved completely opposite, temp is normal when driving at speed on motorways etc however when stuck in traffic they usually rise. And if I'm not mistaken this is the norm, that's why you see plenty of cars on hot days in traffic jams on the hard shoulder lol

Any ideas what could be going on and how to remedy it. Could it be something to do with the gear sync on 4th and 5th gears or the turbo? or maybe water pump is playing up.

Your comments, advice and ideas will be greatly welcome.
Paul