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Old 02-10-2018, 02:32 PM   #7
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,128
 

2003 L-Series 3.0L Sedan
Default Re: Silly question on factory engine block heater.

Engine block heaters heat up the entire engine block, oil and coolant. Since metal takes longer to heat up, electric heaters transfers heat into the engine block that dissipates it throughout the block. Since the engine block is metal, heat is distributed immediately without any hot spots. If you're fingers are sensitive to heat and cold, touching the engine block directly near the heating element may feel slightly warm compared to parts farthest away from the heater. Another way to check for a good heater is measuring the resistance of the heating element with a multimeter. A 120vac heater rated around 750 watts or so may show a value between 8 to 25 ohms; https://bobistheoilguy.com/forums/ub...a_block_heater. Any resistance indicates the heating element is intact and should create heat from ac power. Googling for help; https://itstillruns.com/test-block-heater-6633556.html.

In general, the difference between a very cold engine with temps around 0C/31F or well below freezing will be either slower cranking revolutions and sluggish cold engine running or a normal cranking sound as if the engine were being started in warm weather. Using 0w20/0w30 oil, dino or synthetic also helps with freezing weather startup and running in very cold temps. The 0 in 0w weight oil allows oil to remain liquid and not turn stiff to prevent the engine from turning over in cold weather startups. Heaters plugged in overnight or for an hour or more (timer?) helps warm up the engine block and oil to allow instant starting. This presumes the engine is in good condition with good plugs and started up instantly in warm weather. If the engine isn't starting instantly in warm weather, it may take longer to start up in freezing weather. Heaters help the engine to stay above freezing temps. The EFI system detects the engine coolant temps and automatically adjusts the fuel mixtures - very rich in subfreezing temps, rich all other times for cold engines. Keeping the engine block above freezing temps helps to prevent the engine from flooding on startups. Once started, the engine quickly warms up while the fuel mixtures are gradually leaned out. Heaters used in subfreezing temps are the best mods to prevent straining battery and starter.

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