Hi Bac,
Bacardi wrote:
If the radiator is ok, then surely removing the thermostat should have a marked effect? There was no change when this was tried.
Not necessarily. I'm not sure about the 582, but on a number of car engines the complete removal of the thermostat does not cure the overheating, in fact it can make it worse. Typically there are two water circuts:
1. 'Long circuit': coolant flows through the engine and the radiator.
2. 'Short circuit': coolant flows through the engines, goes through a bypass and flows back into the engine skipping the radiator.
When the coolant's temperature is under the opening temperature of the thermostat, the termostat 'short-circuits' the radiator to make the coolant warm up quicker. Once the thermostat fully open the coolant goes through the radiator and the required heat exchange takes place.
Now taking out the thermostat can cause coolant to partially flow through the radiator and partially through the by-pass. This makes the whole system very inefficient and the overheating problem will persist. But again, this depends on the cooling system's design. There are designs where the failure of thermostat will cause water to be forced through the radiator preventing an overheat. (Most modern cars have this arrangement.)
In my experiences (with cars that is) the best one can/should do as last resort is to slighly increase the diameter of the flow-through hole on the thermostat.
If radiator has been pressure tested, flushed, ensured that there is no blockage, radiator cap valve is in good condition and of correct pressure rating, then I would start looking at the engine: head gasket, warped head, cracks in the cylinder walls, sticky main bearings, etc. But I'm sure the 582 experts will be able to give you much better pointers.