Kinda depends on the liquid cooler. The smaller 120mm rads are good for 140-200ish watts, the 140mm @ 180-260ish, the 240mm @ 240-340ish, the 280mm @ 300-400ish. You have a 140w cpu, push it with all 6 cores at stock voltages and you'll be hitting right around that 140w mark. Understanding that TDP is @ 20-30% lower than possible heat output, if the stock voltages/stepping on that particular cpu are running high, you could be seeing heat output closer to 180w under something like p95 or Aida64. That's going to stress a 120mm cooler and give you temps in the 80's easily. Add in upwards of 100w to a good OC, and you'll be needing a minimum of a 240mm cooler, with a 280mm cooler advised.
At 4.9GHz (upwards of 200w) on my i7-3770K (77w) with a 280mm kraken x61 @1.32v I see 74°max after ½ hr test of p95 26.6 @ 55°C gaming hard. (fans don't break @ 1000rpm) Even a decent OC on a 140w with a 280mm aio, shouldn't be much more, if any, than that. My only conclusion is the liquid cooler you have either isn't performing as it should for some reason, or more likely is not large enough to do the job adequately. A Corsair H60 has basically the same performance as a budget CM hyper212 evo, for instance, which is wholly inadequate for your cpu under anything more than idle loads.