Problem: Oil pump chain snap
Cause: unknown the only think I can think is metal fatigue
Should we change this as precaution?

2008 ml320 cdi
380 000 KM (not miles)
Original turbo
Original DPF
Original Timing Chain
No oil leaks
No burn Oil
Original A/C and freon
original alternator (replaced pulley only)
Original starter

Below are the items that i have replaced all in KM
Engine oil every 6000km to 8000Km
fuel filter every 30 000 KM
Air filter every 50 000 KM
1x pressure dpf sensor (Less than $100)
1x Oil cooler kit (Less than $500) replaced roughly 100 000KM ago
1x Power steering pump (Approx 100 from AliExpress) replaced roughly 100 000KM ago
1x glow plug module ($100)
few glow plug (I think 2 or 3) $40 each
1x oil filter gasket ($10)
1x vacuum pump gasket
1x serpentine belt ($20)
original serpentine belt tensioner
few idler pulley ($15 each)
transmission, transfer case oil every 50000KM
Diff front, rear every 60000km
repair driver side lock
1x Costco battery and 1x amazon aux battery
1x rear light gasket
1x steering rack bushing
1x rear shock
original front strut
Swirl motor flap bypass
Original EGR
No sludge or metal (oil pan was clean)

I currently own 2008GL CDI 200 000KM, 2008 ML320 CDI 380 000KM (RIP), 2012 ML350 Bluetec (120 000KM).

I would like to share how much I spend entire life of my 08 ML320 CDI and i am not complaining about my car in fact I am happy the car made close to 400 000KM.

Story of my chain snap
It was November long weekend a year ago. Took my wife and 2 my kids to vacation. Approx. 10PM 600KM away from home the engine was shake and off. I was thinking the engine seize. Checked the oil level was full so I started the car, and it was on, but it was shake badly and turn off again.
Opened oil cap and my top was dry, removed my oil filter cap and it was dry. I could tell there was something wrong with my oil pump and was not sure what. A tow truck pass by about 30minute later and I asked if they could tow back to my home.
Fast forward summer 2023, I decided to remove my engine since I have 2 other OM642 and would like to find out what was wrong with the engine, and I found out the oil pump chain snap.
Both my top end looks good. I will start removing the bottom end and see if any damage to bearing or not.










I also have tips to share and maybe someone already talked about this or not.
I see many posts about timing chain slap and spend the money to replace chain tensioner. This tip will apply to all OM642 (single or double chain) how to measure the timing chain stretch or not before buying new tensioner.

1. rotate the engine manually first to tighten the chain or to remove right side chain slack

2. removed your tensioner

3. Measure your chain tensioner. Fully extended chain tensioner approx. 3"



4. Use long flat screwdriver or another tool, put inside tensioner hole and press it hard. put mark where the surface of chain tensioner hole is in your screwdriver and measure it.




5. Compare it with the full extended chain tensioner with your screwdriver and you will see if it is stretch or not.

In my case my chain was not fully stretch. It was roughly 2.75". I think if you put brand new chain, it will be about 2.5". Measure it before spend money in new chain tensioner.







Next is about Top dead center.
Pay attention to the dot because the dot is on the tooth and off tooth. if you rotate these 180 degrees. it will be the opposite and it will still look like top dead center, but it is not.

 

With that many miles (ok, kilometers lol) on it, I’d say virtually any of the original components could die at any time. You’ve done well to get this far with it!

 

Yeah I agree. Now I am debating if I should replace my other OM642 oil pump chain.

 

If the mileage is similar to the one that broke, then probably. I’d also be worried about the timing chain at that mileage too.