Leaking Coolant Reservoir?

I have a 1998 Ford Ranger and I recently noticed that my coolant reservoir was empty. I thought it was strange because I had just gotten the coolant system flushed, so I thought it should be full. I filled the reservoir on a Sunday, and by Tuesday morning the reservoir was almost empty. The radiator itself has plenty of coolant, but I’m wondering what the best way is to check for leaks between the reservoir and the radiator. Should the car be running? Warmed up? Thanks!

You could be losing coolant anywhere in the cooling system. Run the engine long enough to warm it up and look for leaks, then turn off the engine and look for a few more minutes. ( I once had a radiator that only leaked after the engine was turned off)

If you cannnot find an external leak, you may have a leak inside the engine.

Seems like the cooling system wasn’t full, which is par for the course after flushing is done. If there are no leaks, your system should draw coolant out of the reservoir until it has enough. Keep adding and the coolant will stop being drawn into the radiator soon. It’s designed to do that.

I’m hoping this does the trick; much easier and cheaper than dealing with a leak in the system, especially if it’s in the engine. Thanks!

While you’re doing that keep an eye on the bottom of the oil filler cap. If it turns up with light brown sludge you may find an internal gasket leak.