Corsa-B.uk - Vauxhall, Opel and Holden Corsa B Owners Club

I have a 1998 Corsa 1.4 automatic and I keep having overheating problems.
Before anyone says head gasket please read on with an open mind. I took it to a local garage who checked it over and said it was the thermostat. They replaced the thermostat water pump and timing belt and because the radiator was starting to weep at the thermoswtch they replaced these as well. After about two weeks it started to overheat again so I took it back to the garage and they diagnosed a faulty thermostat, which they changed free of charge as it had only been changed a couple of weeks earlier.
Every time it's been drained down its had a coolant flush.
So I was very surprised that coming home it started to overheat after only a couple of weeks. I took it to the garage again and they are refusing to sort it out as they says it can't be the thermostat water pump radiator or thermoswtch as there all new.
I have looked at it and just before the coolant comes out of the expansion bottle I felt the top hose going to the radiator and it was cold. The bottom hose was cold as well it seems to me that the water isn't circulating around the radiator which in my mind would indicate the thermostat being in closed position.could it really be another thermostat needed or something else?. I don't know what else to try. Any help would be appreciated.

Could be a blocked rad or a block somewhere else

Your not losing any coolant? And your using coolant not just water? Basic questions but you didn't say so I'm double checking

Thanks for the reply the car is not losing any coolant and I'm using coolant not water. You say it might be a blockage what's the easiest way to check cheers

Take top left and bottom right (or vise versa)hose off the rad and put a hose in the top and see if it runs out the bottom

And basically the same principal for everything else just run the through it

An update on my corsa. I decided to change the thermostat again this time for a genuine part. Whilst I had it out I flushed the engine block and it was clear no blockage at all and the coolant was lovely and fresh. I also flushed out the new radiator and that was the same so I can rule out bad circulation.
I refilled the cooling system with coolant, I undone the sensor on the inlet manifold to vented it like it says in the Haynes manual. I went to start it with the air filter box off and it started to run then it backfired through the throttle body, a flame came out. Now it won't start, it doesn't fire at all so I done the paperclip test and got code 0200 which when I googled it means low voltage or open circuit on the injection system.
I have checked the fuse and I can smell petrol so it's injecting fuel in. Has anyone got any ideas what it could be and how to rectify it ? I thought I might have knocked a connector when I was disconnecting the hose prior to flushing but as far as I can see they all seem ok. I have disconnected them and checked them for corrosion but they all seem fine
Thanks in advance
Darren

You did the worst thing imaginable tbh starting a Car with no air filter is the same as cutting its proverbial wrists

I don't even know where I'd start to look for the problem tbh there could be anything lying anywhere in the engine