You have to ask yourself what's different between a torque wrench and a breaker bar. The answer, of course, is that the former has a knee at the head, normally held in place by a ball and detent which is preloaded by a sprung mechanism in the handle when you select the required torque.
This mechanism is all critical to the calibration of the wrench, and if you distort any part of it, the wrench is scrap, as its accuracy will be compromised. It's all going to be much more fragile than the head of a breaker bar, clearly.
The manufacturer will have designed the head to be strong enough to cope with the wrench's maximum torque, smoothly applied, plus a bit of margin. If you use the wrench beyond the maximum torque rating, either loosening or tightening, you have no way of knowing how much torque you are applying and whether it's beyond a level which will distort the components around the head.
You want the wrench to be accurate, as the safety of your car ultimately depends on it, you can't guarantee this if you use the wrench beyond its' rated torque, so it's wise not to do it.
Author
Topic: Using a torque wrench to undo. (Read 3335 times)