Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of truck and engine maker Navistar (NYSE: NAV) climbed as much as 16% today after the company reassured investors that it was on a path toward profitability in its quarterly earnings report.

So what: The company's adjusted third-quarter loss was $1.63, sharply down from a year ago and below estimates, but revenue topped analyst expectations by more than 10%. The stock has been in free fall lately, losing nearly half its value since the beginning of the year, and a new management team was installed in last month to get the company back on track after an unsuccessful engine emissions strategy. Management did not provide guidance, but said it could "deliver significant improvements during the next 12 to 18 months."

Now what: With a P/S ratio of just $0.10, this beaten-down stock looks a classic turnaround play, but a $100-million pre-tax loss indicates there's still much work to be done. Navistar expects significant cost reductions through layoffs in 2013, and its departure from its failed exhaust-treatment process could help revive the stock, but I'd like to see clearer evidence first before getting on board.

Want to say up to date on Navistar? Just add  Navistar International  to your Watchlist.

Fool contributor Jeremy Bowman holds no positions in the companies in this article. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.