The PO on my 99 replaced the delivery valve seals at 60k miles in 2007 (along with all the fuel lines). Sounds way too early to me...but perhaps it was preventive on his part. On my 98 the seals are original at 92k miles. Think I'll have to do them soon? Or could they go a lot longer?

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

When you do replace them you could use Viton O-rings or if someone chimes in and tells you that the Mercedes Dealer O-rings are now Viton.

In the last 3 years or so there has been more then a few people that have manged to bugger the job and it is not clear what they did or did not do that caused the issue.

Personally I would not replace them unless they were leaking.

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84 300D, 82 Volvo 244Gl Diesel

I agree. There seems a negative possibility even if remote to consider a pre failure approach with these. Leaving well enough alone is not a bad thing in a few cases. I do not even think it is well known exactly why the change does not work out for some.

I am a believer in preemptive replacement of some things if not many as well at the same time though. I always figured it was always cheaper than becoming a roadside issue. If the seals become bad the car will still remain functional enough to avoid this. So not really enough gain to justify it. Just my opinion though.

My om606 is going on 225k on original seals. My om603 started leaking at 210k

Heard from PO....he did it as preventive maintenance while he had the IM off to fix leak in shutoff valve.

On the 602's I've owned, they started leaking at 101k and 181k.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

My '97 delivery valves started leaking around 200,000 miles, but I don't know if those were the originals.

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Charlie

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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)

If they start leaking, then do the repair. This is the type of repair that gives you plenty of time to fix, and will not disable the car overnight.

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96 E300d

x2
Shops do tend to charge high amounts for those 6 orings as they call that "IP pump rebuild" and my friend drives W210 with new IP at around 100k that PO replaced on shop advise.
I was replacing those orings on 603 engine at 290k. Don't know if they were factory orings, but likely they were.