I replaced the timing belt and water pump at 140,000 (I know, I was lucky). At 144,000 the water pump shaft broke (my luck failed on that one!) which in turn caused the belt to slip and break the rockers. When I drained the radiator I noticed metal filings in the fluid (see pic). Do I need to flush out the engine/radiator or will all of the loose metal filings, which I assume came from the innards of the broken water pump, just settle to the bottom of the radiator, or wherever else they may be hiding?

I would flush it out the best you can, all those filings could take out the water pump seal over time. But I also would not lose sleep over it, the filings will fall to the bottom.

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2006 Jeep Liberty CRD
1998 Beetle TDI Malone Tuning Stage 2
2001 Dodge Cummins
2005 Dodge Cummins
ASE, OBDII / VAG-CAN scaner / Service Manual

A magnet is your friend. I would scrounge one of those really strong rare earth hard drive magnets and epoxy it or wire it to the outside of the bottom of the radiator next to the return hose.

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Grid power- the one true essential

2005 Liberty CRD- ARP studs, Fumoto, Hayden FC, inline Tstat, ETechno 7v GP, Platinum P1, in-tank lift pump.
1983 Volvo D24T
1981 Volvo D24
Dodge Cummins TD
Case 580B
Mitsubishi MT180 diesel
Kubota BX25 diesel

Wow, sorry about your bad luck!
Had you been hearing any noises before the failure.
This makes two water pump failures reported that took out the rockers.
I'm glad now that I replaced a seemingly good water pump at 103,000 miles.

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TWO Identical 2005 Liberty Sport CRDS
#1 CRD, 174,000 miles. Eco tune, Samco hoses. Mobil1 0-40w used since day one
#2 CRD 143,000 miles. Bought used (unknown history) with 100,000 miles. Samco hoses.
Eco tune, new rockers, and 5 volt glow plugs installed at 124,000 miles