Just got a new to me 2015 GX460 Premium with 70,000 miles. I noticed the coolant overflow was at the bottom so I filled to the full mark with Toyota Pink. Now I check 2 weeks later and it is down again at the bottom of the overflow tank. I've never seen this truck leak a drop of coolant and I don't see any residue under the truck from the famous cylinder valley leak.

Do I just keep filling the overflow until it stays at a normal range? All my other vehicles didn't have an over flow and only a radiator so I'm a little confused on how this all works.

 

Yes, I would continue to fill the overflow to the max level and monitor. The coolant level may have just been low. I would also look for pink (coolant) staining at the water pump and you may also wish to search this forum for the term "coolant valley leak".

Hope this helps!

 

For start, get yourself a new radiator cap and check out the what @BlueOnyx mentioned.

 

2015's shouldn't have the coolant valley plate leak since the gasket material was changed in 2014. That is unless there is a catastrophic problem. I'm willing to bet it's the radiator, hoses and or water pump.

The best thing to do is track down the leak. Start up front then work your way underneath. If there is crusty pink residue on the trans ball housing it would likely be from the coolant valley plate. Otherwise really dive in the engine bay with a bore scope camera to get in right places and find that pink stuff.

 

I have a 2015 and it had the coolant valley plate leak. It also had a radiator problem as that was replaced before I purchased it.
You'll need a devise like this to check for the coolant valley plate leak:

 

There is another recent 2015 as well on.IH8mud.. latest I’ve seen is around 2016 in a 200 series with the 1UR-FE in GCC market

 

So it sounds like this gasket material wasn't changed? Or maybe these 2015+ vehicles are starting to have the higher mileage to start to have this issue?

 

I think jury is still out.. not sure

 

For what it's worth, this was the first sign of my coolant valley plate leak as well.