can someone tell me where to look for the block heater, if i have one for my 79 300SD (w116), thxs ahead

The threaded plug for mounting the block heater is located on the left side of the engine block when looking at the engine from the front (if sitting behind the steering wheel then it is on the right side). If there is a block heater already mounted, this is where it will be. There should be a short 110V electrical cord connected to the heater (if there is a power cord connected to the heater it may be wrapped around some other components inside the engine compartment and hidden from view). The plug/heater is located about in the middle/center of the engine block, almost directly behind the linkage rods for throttle control and transmission oil pump control, slightly in front of the back end of starter motor, and slightly behind where the exhaust manifold and header pipe are joined. On my car it is easier to see it with the air cleaner assembly off, but you can see it through/around the manifolds with a strong light and getting the right angle. Or, you can see it from underneath the engine. If there is no heater mounted, then look for a large diameter plug (about 45mm or 1-3/4") with a large hex head (19mm or 3/4" - same dimension like 13mm and 1/2" wrenches & sockets that can be used interchangeably).

Good Luck!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

One additional comment on the originally equipped heaters, they came with a detachable cord that plugs into the heater like an electric home appliance or computer. In some cars the cord has long since worn out and been removed, while the heater still remains.

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold