when it is cold can the reserve tank be at low? it is at low now but when the engine is warm and been running the reserve tank is in between min and max. it is a 94 civic dx...the car temp gauge is completely fine and where it should be and there are no visible leaks under the car or on the engine or the radiator and the hoses dont leak. thanks again guys
Do you have an owner's manual? It states what the level should be.
The rule for your 94 Civic is to make sure the coolant is at least the reservoir's low mark when the engine is cold. Then run the engine to warm it to normal operating temperature (so take a trip to the store or something). Turn off the car. Then check the reservoir level again. Add coolant as necessary to bring the coolant to the high mark.
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has a complete manual for your Civic that discusses this and also air purges of the cooling system. Air in the system can mess up your level readings, among other things. A proper purge, using the manual's procedure, will get rid of all the air and also top off the coolant to the correct level.
the tank is more an "expansion tank". The coolant expands when it heats up (like most things) and needs a place to go so it is held in the tank until things cool down again and then it is pulled back into the engine. So what you are seeing is normal operation of this sytem.
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