07-12-15, 11:53 AM
(07-12-15, 09:35 AM)His Dudeness link Wrote: 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.
All valid points, but just flushing with a hose doesn't really do anything other than remove loose particles, it's the crud lining the walls that really needs removing, and which causes the narrowing of the circuit, the same as descaling a kettle.
If the thermostats are that cheap then I'd maybe just change it anyway for peace of mind though.
I can't imagine the fan being a main cause, those buggers rarely switch on anyway.
More people are born because of alcohol than will ever die from it.