Cooling system leak

I have a 02 Nissan Altma 4 cyl. with 95000 mi. For a year now I have been losing radiatior fluid. I have to keep adding it to the over flow tank, I can go anywhere from 100 to 300 mi. and Ill need to add between a pint and a quart. There are no sign of a leah no drips, no puddles in driveway, no wet carpet in the car by the heater core,no puffs of smoke when the car is started. The car runs great!With the loss of fluid air is getting into the system, and when the cer is started for the first time every day I hear this loud sloshing comming from the heater core. The core is the highest point. And that sucks,in the winter I need to go about 80mph to get any heat.The car has been to the dealer six times now they cant find anything wrong, they pressure tested the system, its fine ,checked cylinders with bore scope no leaks, all they do is bleed the air and add fluid. Any help would be greatly appreciated. Thank you Joe71234

One thing that can cause a loss of coolant when there are no apparent leaks is a weak cooling system pressure cap. If the pressure cap opens at a lower pressure than it’s rated for, coolant can escape from the cooling system as a vapor. Try replacing the pressure cap to see if that prevents the coolant loss.


Thanks Tester. The first thing I thought of was the cap, and I replaced it

In that case, there must be a leak somewhere. When a cooling system pressure test is performed for this complaint, it should be done with the engine cold and hot. If this still doesn’t reveal the leak, then the next thing to try is to introduce a tracer dye to the cooling system. Drive the vehicle for about a week, and then using a UV lamp inspect the engine and all the cooling system components to see if this dye shows up anywhere.