I have been a self employed mechanic since 1981, servicing the sea scallop fleet based in Virginia and North Carolina. Most of the vessels are Caterpillar powered. I love the Cat 3412 engine but I will work on anything. Sometimes this involves a learning process.

A customer brought in a Freightliner Cascadia truck, a Detroit Diesel DD15 engine with water in the oil. Number two cylinder liner was cracked. I installed new cylinder kits and bearings.

The cylinder liners are counterbored at the top and have an insert installed with a somewhat smaller inside diameter than the cylinder bore. This insert will scrape carbon from the upper side of the piston so carbon build up on the piston would not rub the inside of the cylinder. On some engines this will superpolish the cylinder wall causing compression blowby and oil consumption problems. I was impressed by the engineering.

The ring compressor is available on the web but be sure to purchase one that includes a carbon scraper adaptor.I fabricated one with a step cut in the bottom to include this feature and it worked well.

The oil filter has a plastic stand pipe inside that includes a filter bypass valve in the top end that was broken and parts missing. I replaced the pipe and never had a problem, but now I see why the service manual says if this happens “call customer service”. These broken parts go directly into the main oil gallery.

The truck went back to work and later had oil in the water. Another mechanic resealed the oil cooler to fix this. So remove and reseal the oil cooler during an overhaul. It looks complicated or impossible but really not a bad job.

Some months later the oil filter cap cracked, probably from over tightening. All the oil blew out and damaged the crankshaft. Follow the torque spec printed on the cap. These are plastic parts.

I fabricated an engine lifting bracket, blocked the transmission in place and removed the engine. The engine was disassembled and all oil passages were cleaned. I found pieces of the old oil filter bypass valve in the main oil gallery. I installed a new crankshaft, turbo, oil cooler and air compressor.

On start up the engine smoked badly and when reved up would stumble and stall. A friend ran a computer test which showed cam and crank angle don’t agree. I replaced a broken cam sensor but no change. Well it was time to admit I could be wrong. I purchased the proper cam timing tools. I had fabricated a cam timing tool that worked fine for the overhaul but this time the intake cam was retarded one tooth.

Off came the rocker shafts and intake camshaft. I marked the cam gear tooth well and reinstalled the camshaft with the timing tool in place. On the first torque the rear exhaust rocker shaft bolt stripped out. Off came the rocker shafts and the rear bearing cap again. The cap had a helical thread insert installed and one had screwed in too far and the bolt pulled it out. I made a thread insert with a 9/16 bolt and installed it with loctite.

This time I wired the exhaust rocker arms for each cylinder together. This kept them grouped together and prevented them from flipping upside down, making installation much easier. The intake rocker shaft is much easier to install.

When started all was well, no smoke and no stumble.

This engine had a self adjusting clutch.  I removed it and thew it aside. After assembly there was only 1/2 inch between clutch release bearing and the clutch brake, The clutch had self adjusted it’s self due to mishandling. The only cure was to remove the transmission and install a new clutch. I thought it was only a clutch but wondered why there was a special section in the service manual on the clutch. Should have read the book.

Time to rebuild the starter.