My l200 2003 runs fine temp wise until you start doing over 55-60mph what could cause this?
Thanks

hello
could be many things
it may be as simple as needing a new rad cap or as drastic as head gasket failure.
why not join the forum (it's free) and see what everyone's views on the subject are ?

Mine is doing exactly the same at the moment, had a sniffer test done and it was good so isn't the head, about to flush the rad out and put clean 50/50 in as I've been told it could be airlocked

It's fine till you hit any speed so not sure as have no idea about motors at all and don't want to take it somewhere and get ripped off really hope it's not head gasket do you mean 50% coolant and 50 water I take it

Yea Daryl 50/50 split, mine rises in temp once I go from 55mph upwards for any length of time. Flush your rad and refill and see if that helps, you know how to do it? Garage won't charge much to do it if your not sure