My mates Berlina temp sits on the very last bar b4 the red bar, thats pretty bad, but when we pull over to check it out, the radiators fine, u can touch the cap and not be burnt (its not hot). I know in mine the radiator cap gets hot.
His coolant is of brown colour, i told him ill flush the radiator for him, but could this problem be the thermostat?
Somethings seriously wrong and hes gonna break it soon i can tell.
Any help? (should i make a cooler out of 2 radiators for him?)
The radiator is probably blocked. It would be best to get it professionally checked/repaired/cleaned. Also it could be the clutch fan not working properly.
first, as you said, flush the radiator and see if there are any blockages, next rip out the thermostat, throw it some bioling water and see if it opens. Is he losing water, could the head by cracked or blown gasket? Maybe he needs a thermo too?
