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Discussion Starter #1
Since retiring my Eos gets very little use and goes for long periods without being started. Over the past twelve months I've had to refill the radiator reservoir three times. The water keeps disappearing but before being taken off the road there was no problem with water loss. Is it feasible that our recent hot weather has evaporated the water!!!?? The car is covered, double wrapped in fact. Just wondering what the problem is.
 

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No, water in the cooling system doesn't evaporate like that, it is pressure sealed. On most of my cars the coolant only gets changed every 60k or 5 years when I change my cam belt and water pump and is never topped up. Just to eliminate the cheapest and most obvious: Replace the pressure cap. If it isn't sealing, the system could be running de-pressurised which you wouldn't notice but when hot, the coolant will overflow so when you get back from having driven the car, vapor has pushed the coolant up into the reservoir and you think it's full. After cooling down, the level will drop.

You could still have a system coolant leak. This is either somewhere hard to see up behind the bottom engine tray, or not visible leaking into the engine either through a bad cylinder head gasket or into oil from a bad pump. Do you get a lot of white smoke (steam!) on first startup after laying up? Most garages can pressure test a cooling system and tell you if there's a leak. If your engine has a cam belt coming up for replacement, have the leak investigated and the water pump changed at the same time. They can also add a flourescent dye to the coolant, run the engine then look around it with a U.V lamp. DON'T put any of these 'leak stop' goos in your system.
 

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Discussion Starter #3
No, water in the cooling system doesn't evaporate like that, it is pressure sealed. On most of my cars the coolant only gets changed every 60k or 5 years when I change my cam belt and water pump and is never topped up. Just to eliminate the cheapest and most obvious: Replace the pressure cap. If it isn't sealing, the system could be running de-pressurised which you wouldn't notice but when hot, the coolant will overflow so when you get back from having driven the car, vapor has pushed the coolant up into the reservoir and you think it's full. After cooling down, the level will drop.

You could still have a system coolant leak. This is either somewhere hard to see up behind the bottom engine tray, or not visible leaking into the engine either through a bad cylinder head gasket or into oil from a bad pump. Do you get a lot of white smoke (steam!) on first startup after laying up? Most garages can pressure test a cooling system and tell you if there's a leak. If your engine has a cam belt coming up for replacement, have the leak investigated and the water pump changed at the same time. They can also add a flourescent dye to the coolant, run the engine then look around it with a U.V lamp. DON'T put any of these 'leak stop' goos in your system.
 
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