OK thanks will go over it all tomorrow, what's best way to make sure it's properly bled also? Thanks!
It could be blocked but I think the fact that it's just the rad that's not heating up points to the thermostat staying shut. The expansion bottle won't tell you what's causing it to overheat just that it is overheating. Once it overheats for any reason it dumps into the overflow. It could be doing that because it's blocked, or it losing pressure because of a leaky hose, a dodgy thermostat cap or I had an o ring fail in the thermostat housing causing it to lose pressure, the thermostat itself could be faulty, it could be low coolant, the fan might not be working, the fan switch might not be working, the pump might not be working. You could even be overheating from a failed head gasket or cracked cylinder letting engine gases into the cooling system. All that will cause it to overheat and dump into the expansion bottle so the empty expansion bottle won't give you any clues which problem you've got. The cold rad though is a clue that the thermostat is stuck closed.There's a chance that the same problem cooked the previous engine too. It'd be a nightmare if you went to the trouble of replacing a whole engine only for the next one to bake as well over a £10 thermostat! In my opinion don't start it again until you pull the thermostat out and test it. You could give the engine and rad a flush by taking a lower hose and an upper one off and stick a garden hose in and flush it out until the water starts coming out clear.
OK so been over the bike, reserve coolant empty and low in rad. Checked bike all over and there was a small clamp at bottom of engine on the left that was a little loose that may have been leaking, had the engine running for 5 mins and the top of the rad started to get hot, that's a good sign right? Also topped up all coolant etc
nom nom nom tastes good If I'm eating my hat your drinking that radflush because we were both wrong! Scale in the cooling system yeah right! Badger in it more likely If he was losing pressure from a lose clamp the coolant might have boiled before the thermostat was hot enough to open so that'd explain why the rad stayed cold.
I reckon the actual problem was that the original poster had been trying to refill his cooling system at the expansion tank and is too embarrassed to admit!...(that's what I did 3months ago because I'm an idiot and thought that's what the Haynes manual said)
It was empty because he changed the engine. ;-)Last time I put my engine back in in a bit of a hurry, It was 3am and I was just doing the last few jobs. I tried filling it with coolant through the expansion tank. Glad I double checked everything the next day.
Also I had the engine fitted around 8/9pm we definitely did it as I bought a second bottle of coolant and water :P