To gain room for starter removal I had to remove 2 allen head bolts on a unit that has 3 or 4 fuel lines to it, one line being from the in line fuel filter. To further my explanation it is at the end of the fuel ine from the in line filer and another line from it goes to the lift pump. I`m very curious as to its function. `85 190d Found it in a Haynes manual listed as fuel system thermostat. Still don`t know exactly what it does.

It's an Engine Coolant/Diesel Fuel Warmer (It uses the coolant [warmed by the
engine] to "Pre-Warm" the Diesel Fuel).

Kinda neat,in the Great Frozen Plains of the US and Canadian Midwest,or if
you're one of those WVO engine gamblers.(Not to mention Northern Europe,
The Steppes,or the Hindu Kush)

'Just another source of Coolant/Diesel leaks for us in the Southeast.

'Looks like this?

Attached Thumbnails

 

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'84 300SD sold
124.128