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.

 

[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.

 

[steve welling]

check heads on 5.3 i have 3 suburbans and 1 yukon xl that the aluminum heads have cracked on. a gm problem.

 

[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 had similar issue with 03 Tahoe. I wrapped a white paper towel around both T connections going in to firewall and tied them on. There was a small leak from both that evaporated and never showed from looking on either side or from the grill, but the coolant showed up on the paper towel. If it is leaking in the summer it will get hot enuff after getting it up to temp and driving a bit further to verify if this is the location of your leak. I have found this method of locating them better than the smell test or looking for residue around the leak. I fought the leaks on the firewall Ts for months, there was nothing visible then got the idea of the paper towel wrap. wah lah!
This sight had a list of leak location on my 03 but I don't think I printed it. I believe someone likely has noted other locales for coolant loss on your model year. Until you find it Carry coolant with you at all times, if it gets worse before you find it, you can be out of coolant quickly if the plastic further deteriorates. Cheers! Murph

 

[89Suburban]

I had similar issue with 03 Tahoe. I wrapped a white paper towel around both T connections going in to firewall and tied them on. There was a small leak from both that evaporated and never showed from looking on either side or from the grill, but the coolant showed up on the paper towel. If it is leaking in the summer it will get hot enuff after getting it up to temp and driving a bit further to verify if this is the location of your leak. I have found this method of locating them better than the smell test or looking for residue around the leak. I fought the leaks on the firewall Ts for months, there was nothing visible then got the idea of the paper towel wrap. wah lah!
This sight had a list of leak location on my 03 but I don't think I printed it. I believe someone likely has noted other locales for coolant loss on your model year. Until you find it Carry coolant with you at all times, if it gets worse before you find it, you can be out of coolant quickly if the plastic further deteriorates. Cheers! Murph

Yup carry extra coolant and I also have a barbed fitting spliced into one of the heater hoses with double clamps so I can bypass that whole she-bang in an emergency failure if it comes to it.

 

[opfor2]

Yup carry extra coolant and I also have a barbed fitting spliced into one of the heater hoses with double clamps so I can bypass that whole she-bang in an emergency failure if it comes to it.

What size "Barbed Fitting" did you use?

 

[89Suburban]

What size "Barbed Fitting" did you use?

I think it's 5/8". I have it located where those brass spring clamps are at on the right hose.

 

[opfor2]

I think it's 5/8". I have it located where those brass spring clamps are at on the right hose.


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