cheesytoejam

Help.
Ok this is a bit long winded but here gos.
When cold car blows steam and smells bit rich until engine at temp and everything ok.
Car overheats after abought half hr at idle. And rockets up if going over 50 on the motorway.
I have run a hose through rad filled from top of thermostat, I've replaced the heater matrix and thermostat.
But still overheating. I tried steal seal so as to see if it was head gasket but still over heats. And water pump was change like 4 yr ago and no leaks.
Really baffled. Thinking I just going to have a go at changing the headgasket and change water pump while I'm at it
Anything else I should change while I'm at it?
Or have I missed something simple to rectify the problem? .
Thanks in advance

RSmark84

header tank cap? these are serviceable items.

GVK.

Are there signs of coolant on the plugs , does it run rough on first start up?

Do the coolant pipes get hard?

Does sound like head gasket.

nigel b

get the cylinder head pressure checked when it is off