I suspect the above has happened to me, my car has been running very well until I did a long drive yesterday (3hrs) and about an hour in it started to overheat at speed, a quick blast of the heater solved it until I could get to the services. No mayo and no gas in the expansion vessel.
I had an issue before with a bottom hose collapsing and this had the same symptoms so I took a spare jubilee clip and clamped it round the hose. This did not help so I removed the thermostat at the next services, this didn't work either so I had to drive with the heater on full chat for the rest of the trip, it's fine at slower sppeds (up to 70kmh) but overheats very fast at anything much above this, all of which made my return journey today a very hot 6hrs.
I'm suspecting the water pump is weak and possibly the shaft is slipping at higher rpm. Does this sound like a feasible possibilty? I properly flushed the rad about a year ago and the coolant is new this month so it can't be a blockage but it's odd that the heater gets hot if the pump has failed completely.
I had an issue before with a bottom hose collapsing and this had the same symptoms so I took a spare jubilee clip and clamped it round the hose. This did not help so I removed the thermostat at the next services, this didn't work either so I had to drive with the heater on full chat for the rest of the trip, it's fine at slower sppeds (up to 70kmh) but overheats very fast at anything much above this, all of which made my return journey today a very hot 6hrs.
I'm suspecting the water pump is weak and possibly the shaft is slipping at higher rpm. Does this sound like a feasible possibilty? I properly flushed the rad about a year ago and the coolant is new this month so it can't be a blockage but it's odd that the heater gets hot if the pump has failed completely.