In the CAT truck world, the 3176 started with serial number prefix "2YG" in 1989-1990. Lots of problems, I've only seen one in our shop in 5 years. Most of "2YG" engines aren't even running. In all these problems, the jake brake "anti-rotation pin" inside the jake brake master piston caused probably 10-15% of the problems. When that broke, the master piston jammed in the housing, thus bent pushrod, thus pushrod fell out, thus bent pushrod went into cam / lifter area, thus ruined cam, lifters and busted out the aluminum (100 mm) spacer deck, thus the entire engine must be torn down to replace cam and this 100 mm Aluminum spacer deck [= all pistons and liners, cylinder head, radiator, front cover, camshaft, oil pan, etc.]

A Jacobs engineer/service rep told me this failure really hurt Jacobs, because their little $1500 product was causing $6000-8000 damage in those early years under their warranty. 

CAT had many, many problems early on, too. The came out with an update (called the "Hotline Update"), there was basically 40 items to repair, inspect, update on this very early engines. We basically were tearing them down and putting them back together on "2YG" engine.

Then in 1991-1993, the "7LG" engine (still a 3176 and still has 100 mm alum. spacer deck) came out. [= big improvement, not perfect, but improvement.]

Then in 1994, the "9CK" engine came out (now a 3176B model, but still has 100mm alum. spacer deck,that seeps oil). The only earlier "real common" problems ,I recall, on this model was the cracked/ broken injector tips and oil leak at cam gasket area= common problem. CAT engineers found the reason for the injector tips cracking was an internal stress riser, once they cured that, this engine wasn't too bad. Some fleets were actually pretty happy, got good mileage and it is a lightweight engine.

NEXT is the big change, in 1995, the C-10 and C-12 came out. Total cast iron block(= no more leaky o-rings, under that Aluminum 100 mm spacer deck, no more alum. spacer deck) YIPEE!!!

The C-10 was actually the replacement for the 3176 size engine. Most people purchased the slightly larger engine C-12, it fits in the same chassis space. I think these engines are good engines for the most part.

I have overhauled C-12s with 950,000 to 1.2 million miles for a fleet we have that just really likes these. They fit their application nicely. These particular trucks ran 26-28 days per month, two shifts. They really clock up the miles that way. 

Bottomline: I only consider a 3176, as the engine with the Aluminum spacer deck, under the cylinder head. [Years 1989-1994]