News from the bunker:
(1) I tried blipping the throttle with the heater matrix exit pipe off. A healthy-looking volume of coolant gushed out each time. Does that mean the water pump is OK?
(2) I have read of people ‘flushing’ the coolant system. what does that entail?
(3) re. bleeding the air out - did that - car is raised at the front on wheel ramps and squeezed the top rad hose until no more bubbles.
Any thoughts guys?
Bill
I had similar problems to you (see my post Hot or not on page 3 of this forum section) and did all the things that you are doing. I removed the thermostat although I new it was fine just so that I could see the coolant moving in the rad. Although it seemed ok (and against the advice of my main dealer) I decided to have a new water pump fitted as I understood they were prone to failure but alas it did not cure the problem. In the end it was the rad restricting the flow, even though it was only two years old. Another new rad and all was fine. though that is of no use to you as you have just fitted a new one.
I flushed mine by removing the thermostat and bottom hose and put the garden hose through each way. Not my choice but you can use something like Holts rad flush, following thier instructions. Another one is Bars Flush. I think Halfords sell both.
Bled mine the same as you.
Do you know for sure that it was the exit pipe from the heater?
I’ve just thought that your overheating ‘could’ possibly be a restriction in the heater? I’m led to believe that the Heater Radiator has no valve … merely a blind affair, therefore I’m guessing that the Heater is in the circuit at all times?
You could by-pass the heater matrix? See how you get on then?
Spot on, so also it makes no difference if the heater is on or off when re filling the cooling system
I have made some progress.
(1) removing the thermostat showed hot water circulating freely with the top & bottom hoses getting hot very quickly
(2) replacing the old thermostat showed hot water not circulating at all
(3) putting the new thermostat in resulted in hot water circulating after 10 mins
(4) the fan starts some time (10 mins?) after that for short bursts
(5) the temp guage goes right up to 7/8 & stays there.
(6) the old fan switch was broken
(7) the old fan relay works.
So it looks like a faulty temp guage or sender.
Condition of the old rad is unknown, but I’m disinclined to swap it back in while the system seems to work.
Bill
Bill, a daft question maybe but has your car got the original dials, or an aftermarket set?
Can you get hold of a normal thermometer, if so pop it in the top of the rad, and warm the engine up, the fan should cut in at about 90 deg C, this will give you some idea of whats happening temperature wise in the engine without the pressure cap—
If the fan is cutting in and out for short periods it tends to suggest that it is not running hot and that the fault lies with an indication/gauge problem.
I agree, it looks as if the temp guage is over-sensitive for some reason. Presumably that narrows it down to either the guage itself or the temperature transducer on the back of the engine?
Bill
Hi Geoff,
Dunno if the giages are original or not, they are the right appearance & certainly look battered enough to be original 
I did try putting a mercury thermometer in the radi cap hole - it went up to 95C earlier and the fan didn’t cut in. Only seems to cut in if I put the cap back on & leave it running for ages.
Bill
Hope we’ve got to the bottom of this. Have changed all three sensors but guage is still reading 7/8 when warm. Those nice men at Autolink diagnosed a faulty guage & they’ll change it this Saturday.
Bill
Fixed. It was the temp guage afer all. Thanks to Andy & Julian @ Autolink for sussing this.
Bill
Glad you got it sorted!
It would be worth noting that to test a guage, take the wire from the sender and earth it - the guage should read MAX - if not, it’s faulty. If it reads MAX then it is probably the sender unit.
Thanks Pete.