Mystery Losing Coolant

[murphyblack]

I am losing about a quart of coolant from my 2009 Chevy Tahoe every few weeks. I have 251,000 miles but the engine and mechanicals have been well maintained and in good shape. Changed the water pump and all hoses last year and recently replaced the overflow reservoir on the advice from this forum to no avail. My oil and trans fluids are clear so no sign of coolant leaking into these. I have no visible leaks on the driveway or garage. I just cannot understand where the coolant is going?? I have about given up and was going to pour in a bottle of Bar engine block sealant but really dont want to do so unless totally necessary.
Does anyone have any other suggestions of where to look??

I found the T-valves for heater up against the Firewall just a touch past the middle of the firewall on passenger side to leak just enuff to allow my Coolant level to drop and the liquid evaporated. Never any liquid on the ground so remained a mystery for a number of years. Mine was so slow, I just carried coolant, checked it regularly and added regularly as needed. It took a while to figure it out. It might be beneficial to wrap a couple of paper towels around those T's with a twist tie so you can see the moisture after they get hot and build up pressure. If you replace one, just do them both. I found another list on this website noting other locations notorious for leaking coolant. Best to you it is frustrating.

 

[Bobio2003]

Next time you shut it off while hot at night, look under the hood and under the vehicle with a flashlight. It helps me find leaks because of the steam.

 

[OR VietVet]

Next time you shut it off while hot at night, look under the hood and under the vehicle with a flashlight. It helps me find leaks because of the steam.

@Bobio2003, you can quote and respond in same post.