Chevy Duramax leaking at Adapter plate

redtom · Oct 13, 2020

We have a Chevy 5500 2004 with a duramax and auto trans where I work. It has developed a coolant leak which I believe is between the adapter plate and the rear of engine. I replaced the gasket on the little rear cover plate on the right rear which I guess is usually the problem, but she still leaks. My question to any Chevy Duramax guys is how common is this? I know the tranny will have to come down to do it and I would like to be sure I'm not over looking anything. Nice thing about this bigger rig is that it has a dog house to get to rear of engine.

Sprint 6 · Oct 14, 2020

Not super common, but it does happen. If this is an LLY, make sure the short coolant hose from the water outlet to the EGR cooler isn't split. When that hose leaks, it runs off the back of the motor. Barring that, it's probably the o rings on the rear plate. That job is not going to be fun. The complete lower and upper oil pan also has to come off in addition to the transmission.

redtom · Oct 14, 2020

Thanks for the input. Nice thing with this truck with the doghouse, I can see right in the rear valley and it looks dry. there are small square "weep" type openings in that plate and it appeared to be coming out the one near that little coolant plate. I power washed the heck out of the rear of engine and now it actually appears to be dripping from the starter mounting flange area.

Chevy Duramax leaking at Adapter plate

redtom

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Sprint 6

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redtom

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