defective oil cooler
If it were my car and I planned on keeping it I would replace it.
I already have to the dealer tune of $600. Toyota recalled this piece in 2011 and replaced the rubber hose. Now the replacement is a completely redesigned part replacing the rubber hoses with steel tubes. Toyota has failed to notify any owner about this change. If the hose breaks the engine will pump all its oil on the ground emptying the crankcase in about 0ne minute. If you are lucky and catch it the repair is easy. If you are on the highway you will end up with a seized engine. NOT so easy. Toyota own each owner at least a warning.
This is a very common problem on 3.5 liter V6 2GR-FE engines
My brother has the same engine in his 2008 Highlander. A year or so ago, the rubber hose you mentioned developed a pinhole, from one moment to the next, without any warning whatsoever. Fortunately, he was able to pull over and shut off the engine quickly, before any damage occurred.
I went to the dealer, and they “just happened” to have the updated part in stock
Fortunately, since I’m a mechanic and do all my own work, we were only out the cost of the part and engine oil, no labor
The recall was for the variable valve timing supply line, not the oil cooler.
Toyota provided a warranty extension on the engine oil cooler for ten years/150,000 miles, owner notification letters were mailed July/August 2014.
The transmission cooler in my '07 Highlander went. Sounds like Toyota has a knack for cooler problems.