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I don't see any active leaks. But I filled my overflow reservoir to max marking last October (cold). And when I checked again today (cold) after almost 1 year, the coolant level is in the middle between min and max of overflow reservoir. I don't believe there is much temperature difference between last October and now to cause this.
What could be the reason? For both last Oct and today, when I opened radiator cap, it is filled to top, there is no sign of pressure drop or leak at the cap.
I guess at the end of day, water pump and valley plate leaks are waiting for me. Btw I have 125k miles on my GX and never flushed coolant so far.
You don't have a problem, the coolant level will find the sweet spot and stay there you can fill it up again and over time the excess will be pushed out the overflow. In other words if you fill to the top line on a cold engine it will not stay that way.
I'm not saying this is your problem, but I had the same symptoms on my GX with 115k, except the coolant was disappearing a bit faster. It ended up being the coolant valley leak. Level has stayed perfectly steady since I had it fixed.
What year is your GX? Earlier 460s 2010 to 14's tend to have the valley plate leak quite commonly due to a bad sealant used at the factory. Check the passenger side engine bell housing from under the truck, if you notice any pinkish stains, then this got to be a valley leak.
My 11GX is also having the valley leak for the past 2.5 years (now at 155k miles), the leak is very minor and I have filled up maybe 1.5gallons in the last 40k miles and didn't bother to fix it. Will top off the overfill tank during every oil change and check the level once every 3-4 weeks when I do a visual inspection under the hood. Will get it fixed once the leak becomes larger, but looking at my refill interval I don't think it will grow bigger.
Looks like your leak is also very minor, check the bell housing or the rear passenger side of the engine and confirm if its the valley leak, if not then check the weep hole on the water pump for any pink crystallization, this is the next common problem after valley leak.
What year is your GX? Earlier 460s 2010 to 14's tend to have the valley plate leak quite commonly due to a bad sealant used at the factory. Check the passenger side engine bell housing from under the truck, if you notice any pinkish stains, then this got to be a valley leak.
My 11GX is also having the valley leak for the past 2.5 years (now at 155k miles), the leak is very minor and I have filled up maybe 1.5gallons in the last 40k miles and didn't bother to fix it. Will top off the overfill tank during every oil change and check the level once every 3-4 weeks when I do a visual inspection under the hood. Will get it fixed once the leak becomes larger, but looking at my refill interval I don't think it will grow bigger.
Looks like your leak is also very minor, check the bell housing or the rear passenger side of the engine and confirm if its the valley leak, if not then check the weep hole on the water pump for any pink crystallization, this is the next common problem after valley leak.
Mine is 2015. I do oil change myself and I have never noticed any pink crystallization so far.
If coolant valley leak is small, one wouldn't notice anything down below unless you were refilling your recovery bottle every month or so. Coolant would just evaporate in the valley.
For reference: I changed a significant amount of my coolant in summer 2021 while purging all air. My coolant level always go back to same cold line when engine cools.. give or take whatever ambient temperature does to level of fluid in that tank.
As stated a radiator cap replacement never hurts to rule out and is relatively cheap.
The radiator cap came, in case you are curious what it looks like. I believe my current one is also OEM but under a different part number, that explains minor difference.
10-23-22, 03:33 PM
Slow coolant level change from overflow reservoir
