2012 Kenworth T660 Cummins ISX15 - Heavy Oil Leak at Rear of Engine

Question

My ISX15 is leaving dinner-plate sized oil spots everywhere I park. It looks like it's coming from the flywheel housing area. I was terrified it was the rear main seal, so I took it to a local shop. They said they think it's the rear gear housing gasket, which is a massive job because the transmission has to come out.

I want to make sure before I commit to 30 hours of labor. Is there anything else high up on the back of these engines that leaks and runs down the housing?

WrenchMonkey_J · Accepted Answer

✅ Confirmed fix: It was the overhead camshaft rocker lever shaft plugs. The O-rings on the rear access plugs flattened out. Replaced the plugs and the O-rings by reaching behind the head. Saved me from a $5,000 gear housing job.

RamRunnerRay · Answer

Check the cam plugs at the back of the cylinder head. These are notorious for leaking on the CM2250/CM2350 engines. It's a much cheaper fix than pulling the transmission.

2012 Kenworth T660 Cummins ISX15 - Heavy Oil Leak at Rear of Engine

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