Duramax Diesels Forum Truck of the Week
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Old 10-11-2018, 12:12 PM
mechman3 mechman3 is offline
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Default Coolant leak back of engine

I have a coolant leak on the back side of the engine. It is sometime a 12" puddle other times a couple of drips. I took it into the stealer and they said the backing plate is leaking. I do not understand the construction of these motors but this seems odd. Can anybody please shed some light on this for me?
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Old 10-11-2018, 12:24 PM
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Could use some pictures of where the coolant is leaking from.
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Old 10-11-2018, 12:30 PM
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The rear cover of the motors is a removable aluminum "plate" (really a complex casting, but only 1-2" thick) that adapts it to either a SAE bellhousing pattern (Kodiak Medium-Duty trucks) or the standard GM V8 bellhousing (normal pickups). The coolant comes in the left side, and crosses over to the right side, entering both halves of the block.

The rear cover off my motor:
Rear Cover.jpg
You can see the two big circular ports with o-rings that seal to the block.

And mounted on the motor, you can see the flat coolant crossover tube, and the blanking plate on the right of the motor:
Rear Cover Installed.jpg
That blanking plate is a common source of leaks. Well, not common, but more common than the ports that seal to the block.
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Old 10-11-2018, 12:34 PM
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Which side?
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Old 10-11-2018, 12:59 PM
mechman3 mechman3 is offline
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I believe it is the driver's side of the back of the motor. I will try and get some pics.
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EGR blocker plate
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Old 10-11-2018, 01:01 PM
mechman3 mechman3 is offline
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Thanks for the explanation and pics they have opened my eyes.
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EGR blocker plate
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Edge Insight CTS
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Old 10-11-2018, 03:07 PM
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If it is leaking on the driver's side at the rear, I would check the oil cooler for coolant leaks and also check in the valley for leaks up there that are running down from up top.
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Old 10-11-2018, 03:43 PM
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Quote:
Originally Posted by JoshH View Post
If it is leaking on the driver's side at the rear, I would check the oil cooler for coolant leaks and also check in the valley for leaks up there that are running down from up top.
X2, if you have a EGR cooler or turbo coolant line leaking, it could just run down the back of the motor like that. Those coolant hoses are pretty old at this point, and having one just spring a leak at this age isn't unheard of.
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