Broken frame to engine bolts

[Diggin It]

I can't figure what caused all the bolts to loosen which I would assume is what caused the front bolts to break.

There have been a bunch of threads discussing various bolts and nuts loosening due to vibration (apparently) and many owner's manuals include inspecting and torquing them periodically.

 

[ruffdog]

I'm thinking that you have 12mm bolts which is slightly less than 1/2". I would start with a 3/16" drill in the center, then use the correct ez-out. Most of the time I will use a smaller drill as a pilot drill before the final size. Just get a good center punch to locate the center first.

 

[Jenkins003]

I took one of the bolts out this evening and ruffdog you are probably correct on the 12mm size. It is around 7/16 by 1 1/2 inches long. I'll try your suggestion of starting with the 3/16 drill bit. I looked at the tractor frame and it appears as a last resort the frame rail on that side would come off but it would be a big job but I believe I can get the broken bolts out without going that far since there is no reason for them to be frozen in there. It may be several days before I get the time to try to get them out. Harbor Freight has a set of transfer punches so I'll pick them up tomorrow and try to find somewhere to buy some quality drill bits and EZ Outs.

 

[5030]

Center punch as close as possible to the center, get some high quality left hand (counter clockwise) drill bits. I was in a similar situation recently, and drilled with a conventional right hand bit followed by easy out, was not successful. I used a CCW bit, it dug in and spun the bolt out immediately. I followed up by running the proper tap into the threads to "chase" them, clean them up a bit.
Success!

Modify that a bit... Use a proper diameter transfer punch and get the punch mark DEAD center.

Apply some thread locker when you replace them and torque properly.

 

[Jenkins003]

Does anyone know what these bolts should be torqued to ?

 

[5030]

Should be a bolt torque chart in your owners manual. If not, post the diameter and thread pitch as well as the strength of the replacement bolt and I'll look it up for you.

 

[Jenkins003]

It appears these bolts are grade 10.9 and the bolt also has an H5 stamped on it if that means anything. They are 1 1/2 inches long and my owners manual has no torque specs.

 

[Tomtint]

It appears these bolts are grade 10.9 and the bolt also has an H5 stamped on it if that means anything. They are 1 1/2 inches long and my owners manual has no torque specs.

Torque them a little less than the last guy did ..lol

 

[mikester]

Torque them a little less than the last guy did ..lol

No, torque them properly and save yourself very expensive repairs

Heres the Kubota specs for a starting reference

 

[5030]

The H5 is the maker's mark and the posted chart will suffice for torque values. I would apply s tab of threadlocker to them as well. Preferably red, high strength.