[-XIs it the old sj rad?Ithink the vit 1.6 is bigger.Have tried back flushing the rad.Diconnect it from the engine and shove a hose pipe up the bottom.(not for those that lead sheltered lives lol)I wrap insulation tape round the hose ad leave it running.If only a bit of muck comes out get some rad cleaner from motor factors.I've got a1.6 8v never had overheating and it got a/c rad in front of it.If you had a head gasket prob,you would have A.white smoke/steam from exhaust,B.oil and water mix,C.pressure in water pushing water out rad when open and D.water loss.Let enginge get hot and check for leaks but make sure system is pesurrised,leave cap on and tight.