Need some technical advice. I have a 93 300D 2.5T. The timing chain broke a few months and toasted the engine. It has since been determined that the oil pump on that motor is toast also (tried to reuse it on a replacement engine...long story). My mechanic has suggested the oil pump went first, and that caused the timing to chain to break. I have a hard timing comprehending that one. At the time of chain failure, i was leisurely driving about 30mph on a quite city street and simply heard a snap on the car just drifted to a stop...there was not a second of other noise other than the metal snap sound (sounded like a drove over a piece of sheet metal on the road). I assume i would have had at least a nanosecond of engine distress sound or engine operation dropoff if the oil pump had failed first, right? what makes sense...did the timing chain or oil pump failure come first?

The oil pump is driven by a chain. If the oil pump chain broke, it could have become lodged in the timing chain and broke it in turn. Oil pumps themselves usually don't "break" but could wear out over many, many miles, causing gradually lower oil pressure.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

that is kinda my point, i would assume had the oil pump caused the problem that i would have noticed oil pressure-related issues. what would cause the oil pump itself to break? it was obviously working fine prior to the incident, but now appearently can't circulate oil at all when installed on the replacement engine. may never know i suppose, but debate over whether the timing chain or oil pump failure destroyed the engine is valuable.

Svengruber,

How many miles on your 124.128s drive-train?

It is not unheard of for the OM602 to suffer an Oil Pump Chain failure,either
from a "Snapped Chain"
OR the *#^&_>@ Oil Pump Sprocket Bolt "BACKING OUT" of the Oil Pump
itself!

EITHER of which could cause the Demise of the Camshaft Timing Chain.

The progression of events may have occurred so rapidly that you did not
notice a Low Oil Pressure Incident,Because the Timing Chain had Already
parted!

MY Personal Boilerplate rule is (NOW):
1.Take the Oil Pump Sprocket Bolt out and Clean and Dry it's Seat in the OP
and Blue Loctite the OP Sprocket Bolt back into the OP(Proper Torque).
2.If the Timing Chain needs replacing ALSO do the Oil Pump Chain System.

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'84 300SD sold
124.128