Mystery Losing Coolant

[MT Driver]

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??

 

[Joseph Garcia]

Do you smell coolant around the front of the truck while idling at normal operating temperature?

 

[opfor2]

Do you have the auxiliary rear heater? If so, check the rear heater core for I have a small leak there which I have not fixed yet.

 

[OR VietVet]

Have you ever pressure tested the cooling system, hot and cold engine?

 

[89Suburban]

The side tanks could be weeping on the radiator. Not enough to notice dripping on the ground. But just enough to burn off once it heats up and gets under pressure. I would take a good look at those areas with a good flashlight to look for any wetness. May even be a small puddle on the support that doesn't reach the ground. Mine was doing that. I put a new radiator in and it's been fine since.

 

[OR VietVet]

With a slow enough seepage and when the wet coolant hits a hot surface, like say on the radiator, it evaporates before hits ground. Then as cools off, the pressure decreases and the leak stops itself.

 

[petethepug]

What he said. Our 08 Denali had a cracked expansion tank and cracked plastic end tank on the radiator. The coolant literally vaporized as it escaped leaving what looks like a little soap residue.

The truth revealed itself on a 100* day, parked idling, front & rear a/c at max cool. The temp & pressure went up high enough to allow the steam to be visible coming out of the cracks. When refilling the truck at home when cooled off, no cracks, just residue showing.

Fix it ASAP. A low coolant issue can destroy a motor by having to run it unnecessarily for getting out of high speed traffic or an unsafe situation. If you turn off the motor or it dies while moving you lose power brakes & power steering so you’re riding a 3T unstoppable mass. Running a motor past overheating is sometimes better than running a red light.

 

[Just Fishing]

I had that before my heater core plastic connectors blew at the T's
I had already replaced the T's, but the one line I didn't touch because it looked perfect.
No sign it was from that, I couldn't see any sign of leakage, just the dex cool smell.

When the lines blew my temp gauge pinned.
On a brand new engine...

 

[Doubeleive]

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??

as others stated and I have experienced myself a slow leak will dry off from the wind and not leave a drop, it will however generally leave a "redish-orange" tint
somewhere....... you will need a flashlight and mirror and start by looking up from underneath the vehicle, you might have to pull the the fans off to look at the backside of the radiator clearly. this includes under the waterpump, around the steam vents on the heads, heater hose T's etc, etc,
also remove any splashguard or skid plates so you can get a better view.
once had a leak out of a hose once that only spit a little toothpick sized leak under pressure-sometimes

 

[Just Fishing]

this thread reminded me, all plastic parts in my cooling system has been replaced.
Except for my coolant tank.

So, I just ordered one.