Do not I repeat do not but Bars Leak into your Toyota! Modern high effecientcy denso heater cores will plug up if you put BarsLeak into the cooling system. GM had a huge issues on the CTS when it first came out with no heat situation in the CTS. THey found that the stopleak being used was pluging up the Denso heater cores they were useing!
Most vechiles do this over time. I would replace the lost coolant with a 50/50 mix of coolant and distilled water. Keep and eye on things and do not let the resovoir get depleted to that extent again. It would be a good idea to check all of the hoses and make sure the area they attach to is clean and clear of deposits.
I doubt your hoses are bad but if you like now would be a good time to replace them and flush the cooling system.
P.S. Is this a recent development or have you had to top off the resovoir before? I ask because I find that I have to top off my resovoir with some filtered water ever 6 months or so. If you have gone 4 years with out topping off I can see why the resovoir is empty.
Most vechiles do this over time. I would replace the lost coolant with a 50/50 mix of coolant and distilled water. Keep and eye on things and do not let the resovoir get depleted to that extent again. It would be a good idea to check all of the hoses and make sure the area they attach to is clean and clear of deposits.
I doubt your hoses are bad but if you like now would be a good time to replace them and flush the cooling system.
P.S. Is this a recent development or have you had to top off the resovoir before? I ask because I find that I have to top off my resovoir with some filtered water ever 6 months or so. If you have gone 4 years with out topping off I can see why the resovoir is empty.