Re: another issue found with my 'zuk
One of many im sure!
A few things to check
Does your coolant level stay constant?
If not you may be losing it through a cracked gasket or head. If thats the case this can be verified by checking the Oil filler cap and dipstick for any gungey residue (this is is typically white when you use water as a coolent, i dont know if you will get the same effect with "proper" coolant"

). There is even a special tool that some mechianics have that will check if oil or CO has mixed with coolent.
Also the thermostat may be broken and jammed shut. This can be checked by feeling the top hose when the engine is warm to see if its hot. If not the thermostats broken.
Also i lost coolent and pressure in my radiator for a pin hole in the radiator cap, which caused it to get pretty warm. This also stops the vacume that sucks coolant from the overflow bottle back into the radiator, so if the overfow bottle is full all the time, then your radiator is'nt holding a pressure/vacume.
(Apologies if im teaching you how to suck eggs)