On the 606 engine (1995 E300D) there is a thermostatically controlled device that apparently runs the diesel fuel through a small heat exchanger that is immersed in the water jacket in the cylinder head. Its purpose (I suppose) is to warm up the fuel until it reaches a certain (unknown to me) temperature. Probably a good idea if one lives in Siberia, but it never gets below freezing where I live.

It is leaking, and the replacement cost is pretty high, especially for a device that I don’t apparently have a need for, and that could in the future go bad again.

I am considering bypassing it, but I am wondering if I am doing something harmful in the long run; I am wondering if it is solely for keeping the fuel from gelling in the cold, or if the injection pump is required to have a certain viscosity fuel available. I hate to second guess the engineers at MB, but…

Any opinions? (Other than that I am a hack? )

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Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.