* UnitedHealth's rise helps Dow notch record
* Goldman shares down after Q3 results
* Indexes: Dow up 0.1 pct, S&P up 0.01 pct, Nasdaq down 0.1 pct (Updates to late afternoon)
By Caroline Valetkevitch
Oct 17 (Reuters) - The Dow Jones Industrial Average breached the 23,000-mark for the first time on Tuesday, driven by strong earnings from UnitedHealth and Johnson & Johnson, but the S&P 500 was flat.
The blue-chip index has surpassed four similar 1,000-point milestones this year, indicating investor faith in the bull-run despite lofty stock valuations. For a factbox, see
But the Dow was unable to hold the level and has been trading below 23,000 for much of the afternoon.
"My view is it may take several days or a couple of weeks before it can sustain a level above 23,000," said Robert Pavlik, chief market strategist at Boston Private Wealth in New York.
"Right now, we're contending with earnings season, and the fact that the market has run up, leading up to the earnings season."
The S&P 500 was flat, with financials the biggest drag. Goldman Sachs shares dipped despite reporting a profit beat and smaller-than-expected trading revenue fall.
Shares of the largest U.S. health insurer UnitedHealth touched a life high and was last up 6.3 percent, after the company reported a stronger-than-expected profit and raised its full-year earnings forecast.
That, along with a 3.6 percent rise in Johnson & Johnson , led a 1.5 percent gain in the S&P healthcare sector .
The Dow Jones Industrial Average was up 29.42 points, or 0.13 percent, at 22,986.38, after briefly hitting the 23,000 mark earlier.
The S&P 500 gained 0.14 points, or 0.01 percent, to 2,557.78 and the Nasdaq Composite dropped 3.89 points, or 0.06 percent, to 6,620.11.
Netflix slipped 1.5 percent after touching a record high as more subscribers signed up for its popular original content in the latest quarter.
Declining issues outnumbered advancing ones on the NYSE by a 1.51-to-1 ratio; on Nasdaq, a 1.77-to-1 ratio favored decliners. (Additional reporting by Sruthi Shankar in Bengaluru; Editing by Arun Koyyur and Nick Zieminski)