I know its summer right now, but someday it will be cold dark and 5 am and frigid again, and I will be cranking my diesel in a freezing passenger compartment.

While preparing to put my 85 300D engine back in, I noticed a second allen plug on the back of the cylinder head. Is it any benefit to stick a second engine block heater there for super enhanced warm up in January?

No, there isn't!

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Good idea if:
1. You still have a block drain.
2. The electric supply can handle it without blowing a fuse or tripping a breaker. You'll have to find out what the heater's wattage is.

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daBenz - 1970 220D

I would think it would help. You'd have nice heat at the start that's for sure. The thing is though is that it would cost a pretty penny to keep it plugged in all night. If the allen screw is the same size why not go for it? If it doesn't help at all either remove it or just don't plug it in.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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There is absolutely no benefit unless you wish to reduce the time that the heaters remain on.

If you plug one heater in for four hours, you could limit this to two hours with two heaters.

Why bother?

Don't you think it would raise the coolant temperature? The coolant doesn't flow very fast so the coolant away from the heater would cool down some. I do agree that it would cut the plug-in time.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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I suppose if you spent the money to run them both all night long, you might get another 10 degrees of water temperature in the block.

But, what for?

10 additional degrees is not going to help it start any easier. It starts fine with just one heater running for four hours or so.

No question if you put twice the power in the block you will raise the final equilibrium temperature -- it could be quite a bit higher too. It would help in a very cold climate where the heat loss is greatest, but my vehicle had no cold starting problems this winter (outside, occasionally down to -20F).

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'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

I would install 2 block heaters. In winter I would plug them in using an extension cord that extends into the house. In the morning I would plug in the extension cord, go have breakfast, and let the heaters heat up for an hour. Then go and start the car. I have used this system for years on gas and diesel engines. I live in southern Canada.

One block heater for four hours starts my sedan at -30*F with ease. The trick is to plug into a heavy duty timer so you don't have to walk outside to plug it in.

Two block heaters would heat it twice as fast or get it ? degrees warmer, but I doubt the slightly quicker passenger compartment heat will be worth the cost of the extra heater and the cost of running two heaters for four hours.

Good luck!

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1983 300td 240k (down with bad tranny)
1984 300d 222k (daily driver) "Olive"
1997 GMC K2500 105k (sled dog limo)

"The scenery in ANWR is as spectacular as the Grand Canyon and the wildlife is more impressive."

The single heater worked great for me all winter. I guess we didn't set any low temperature records this winter yet NH is NH and cold winter is cold winter. Even with my set of new glow plugs still in their boxes instead of installed as they should have been the single heater did the trick. Just can't imagine why the second one would be needed

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Steve
'87 300TD - 132K - Soon 4-Sale
'84 300D Turbo - 122K - Driving
'77 VW Type II - 77K - Restored
'08 250EX Ninja
English Bulldog (Brier) - My best friend. Passed away 12/02/04 while in my arms.

Would 2 heaters restrict coolant flow?
There can not be much of a coolant passage in the head to begin with.

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82 Rabbit diesel (first d), 84 Jetta turbo d (300k when sold), 83 240d (305k when sold), 84 F250 6.9d w/Banks turbo(parts truck), 86 F250 6 cyl.gasser(waiting for 6.9d), 84 300d ( 347k Sold 8/04), Y2k New Bettle TDI (185k miles), 95 740IL (wifes), 87 300TD (206k Sold 7/05), 05 Passat TDI Wagon