During the rebuilding of our prechambers we found that the socket head capscrews that secure the upper and lower halves were too long and bottoming out in their holes. This was discovered while troubleshooting oil leaking into the sparkplug bores on 6 of 18 cylinders of one unit.
Measuring the holes with a depth micrometer, we found the bore depth matched the screw length exactly, with no room for stretch. In other words, the screws were bottoming out in the bores when torqued and not providing adequate compression at the sealing faces of the prechamber.
Approx. 3 threads were cut from the ends of the screws to prevent bottoming in the bores.
Feel free to contact me via email for details and photos, as I can’t attach photos to this post.
Dave – we recently had two issues with the PCC admission valve screws/bolts. In both cases the symptom was a cold cylinder. In one case the two screws were broke and in the other case the two screws were loose. Wartsila is still investigating. If you want more information you can email me at email@example.com
Thanks for the heads up in the prechamber that holds upper and lower body’s, we will take a look in ours since recently we had one similar situation , Also as Mark is mentioning, we have had either broken or loose bolts in the piece that holds the PCC valve in the Yokes, we added in our 1k hours the inspection of these bolts, just inspection not to double tight since they are loctite “supposedly” torqued. We have been able to identify more loose bolts were we have to add loctite and torque them as Wartsila specs.