Some bad news !
I got a new torque wrench that was defective resulting in the over tightening of this bolt that cracked the block.
This is the end of the road for this machine. No more money can go into it. The bolt will hold the 94 pounds of torque required.
See photo...
Is there any hope?
You should of went by the Yanmar engine service manual.
It is very possible to save the block. Especially since the damage is on the very end. This is a positive for you.
You can do this just fine with the block on the tractor too. Just mask off the other areas.
How to repair a casted block bolt hole on the outside perimeter.
- On the outside wall of the block, grind each crack as far down as possible in a V or U shape some 3/16ths (4.8mm)
- Wire wheel clean 1/2-in (13mm) on each side of the new groves you just made.
- Drill small holes at the base of the crack to prevent the crack from going further.
- Clean the entire area. Not with oils nor water nor WD40.
- Due to the nature of this crack repair for size and the bolt hole, install an unthreaded stud into the bolt hole that will resist being welded. Some people use a hardwood dowel, do not use plastic. This will prevent weldment material not to fill the hole.
- Use a wire feed welder with .035 stainless steel wire and a tri-mix gas of Co2, Argon, and Helium.
(why use this method, this applies only localized heat on the casted block. you do not need to change the casted block hardness to become brittle.)
- As the 1st layer of weld is 1/2 cooled, wire brush over the top of the weld. Until fully cool.
- Apply the next layers until you have built up weld to the outside for each groove made and layered into the outside wall previously cleaned up to 1/2-in (13mm) each side.
- Pull out the wooden dowel. It may break, typical, but easy to use a pick to clean out the hole.
- Let this all cool overnight or over 6hrs.
- You can re-tap the hole slowly and carefully. Little each time and clean out each time as you go down.
- New head bolts and STI Helicoils are a must. You would need to size the hole for the insert.
Heli-Coil® Taps & Gages | STI Taps | Screw Threaded Insert Taps | STANLEY® Engineered Fastening
www.stanleyengineeredfastening.com
For the Helicoils, use Loctite 2620 or in a pinch 262.
How to Install a Helicoil That Won’t Retract
Both the Deere and Yanmar Service Manuals mention how to bolt down the head in a stage by stage and sequence method.
@rScotty can even comment on what sealants are possible and to use it SPARINGLY.
Others who have had perfect flatness with heads and blocks take their time in each stage for torquing. They will let the head sit awhile before the next stage, ensuring the stress gets properly relieved.
We've heard others who don't weld, followed this basic procedure mentioned above using JB Weld. Personally, I've not used the stuff to make any valid claims JB weld would work.
Let's save your Yanmar in JD green paint.
