We’ve been overhauling a couple of Caterpillar 3408 engines for a marine operator recently, and during the initial inspections, we came across something which could easily lead to engine failure if missed.
The engines arrived at Bartech already dismantled, on various pallets, and after visually inspecting the crankcases, we found machining swarf in both units.
Although we had been informed all components were within tolerance, as always, we carried out our own in-house measurements; essential for us to guarantee our work.
The bores for the main bearing journals were all within specification, and it could be seen that they had been machined (the cause of the swarf noticed initially!)
Next inspection was the distance from the pan rail to the centre line of the bore by machining a jig to fit into the bores and then measuring down from the pan rail.
This critical dimension was outside its limit, affecting the gear backlashes!
Knowing the bearing journal bore diameters were in specification, this inspection showed that although the crankcase had been line bored by the previous service company, instead of boring out to the next size for oversize bearings, it seems they bored it off centre, causing the issue.
The result was a crankcase that requires extensive rectification work (or replacing) to reduce these backlashes and protect the gear teeth from the oil pump and the idler gear from breaking up.
If we had trusted the information provided, just rebuilt the engine and the gears broken up into the engine, there could have been some major consequences.
