looking at buying a 99 E300 Diesel that has been under water.
what to look for ? Is it even worth my time and money to try to fix up.

Run away from that deal as fast as you can. There are so many electronics in a W210 that it would never be right.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

nothing that $28,000.00 will not fix. LOL....

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Now you say underwater... What do you mean, underwater?

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#dieselFLEET
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'97 E300
'99 E300

If it was fresh water it may not be to bad, how far under? Does it run and drive? If the dash didn't go under and it was fresh water, and the engine was fired up right away.

I'd stay away.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200