So, in a past post about this retorque proceedure i argued that if each bolt was not removed, oiled up on the threads and underside of the bolt head that you didnt do anything because you didnt overcome the friction set of the bolt head and threads. Most will find that if they just put a TORQUE wrench on and try to tighten the bolt without breaking it free first, that they will not move before the wrench reaches the spec. I said that if they did not first break the bolt free they wasted thier time and did nothing, and challenged anyone to test my advice.
Well i did my own tractor this weekend and even though i already knew what the outcome would be i did 8 bolts (8 was enough to get a good average) as a test for you guys to proove a point. What i did is took a paint marker and drew a line across 8 of the bolts down onto the head to mark the original position. I took my torque wrench and tried to just see ANY OF ALL OF THE bolts would turn with just trying to bring the wrench up to the torque spec, and as predicted none moved.
Then i did the proper method and starting with the middle bolt, i broke it loose and removed it completely and re-oiled the threads and underside of the bolt head and reinstalled it. I then torqued it to specs and looked at the paint mark. I did this to all of the bolts and only did one at a time so the gasket surface would not lose clamp load. What i found on all the painted bolts is that they turned an average of 15 degrees more that the original position. A couple were only 10 degrees but a few were 20 degrees. That is a lot of movement and added clamp load when you calculate out the bolt diameter and thread pitch. This friction locking i am talking about is what makes bolts make a loud snap or creaking noise when breaking free. It usually takes much more torque to remove this friction set than to actually retighten them to the original position.
I did not drain the coolant either. All i did was crack the radiator cap to be sure there was no pressure built up.
Just figured i would let you know my findings so you guys can think about it next time you have to do this.
Schmalts
Well i did my own tractor this weekend and even though i already knew what the outcome would be i did 8 bolts (8 was enough to get a good average) as a test for you guys to proove a point. What i did is took a paint marker and drew a line across 8 of the bolts down onto the head to mark the original position. I took my torque wrench and tried to just see ANY OF ALL OF THE bolts would turn with just trying to bring the wrench up to the torque spec, and as predicted none moved.
Then i did the proper method and starting with the middle bolt, i broke it loose and removed it completely and re-oiled the threads and underside of the bolt head and reinstalled it. I then torqued it to specs and looked at the paint mark. I did this to all of the bolts and only did one at a time so the gasket surface would not lose clamp load. What i found on all the painted bolts is that they turned an average of 15 degrees more that the original position. A couple were only 10 degrees but a few were 20 degrees. That is a lot of movement and added clamp load when you calculate out the bolt diameter and thread pitch. This friction locking i am talking about is what makes bolts make a loud snap or creaking noise when breaking free. It usually takes much more torque to remove this friction set than to actually retighten them to the original position.
I did not drain the coolant either. All i did was crack the radiator cap to be sure there was no pressure built up.
Just figured i would let you know my findings so you guys can think about it next time you have to do this.
Schmalts
