I am looking to install an Espar Hydronic unit on my SDL and have a couple of questions. Can I use existing plugs in the block to install or maybe remove the block heater to plumb in the Espar unit? What are the locations of the extra freeze plugs on the om603 engine?
If I had to tee into the heater core lines, does the coolant flow from passenger side of the block to heater core and back to drivers side of the block?

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1987 300SDL-268k mi

I'm not 100% positive on the SDL as I only have an 84 SD, but I would assume since they are both 126s they are similar.

I think you are confused on the role of the espar. If you installed one you would leave the original stock block heater completely alone.

I have only looked at Webasto diagrams but would assume they are similar to Espar's. They show that the coolant lines should be tapped where the coolant line EXITS the engine and BEFORE the heater core (on my 126 the is at the rear driver's side of the engine block). This way it can defrost your dash and if you hook it up to a relay it can turn on your blower to heat your car. Then the coolant flows through the rest of the system, including the engine to act as a block heater.

EDIT: I forgot there are 2 types of units. One to heat the coolant and one used just to heat the air inside your car. I was talking about the one used to heat the coolant.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

Yes, I forgot the block heater heats oil and not coolant (Duh). I have the hydronic type that heats the coolant.
When tapping the the heater core lines, would the heater need to put in series with the heater core or in parallel? Thanks for your help.

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1987 300SDL-268k mi

The ones I have seen tap in parallel. Think of it like this- The coolant line from the block to the heater core is cut in two places. First tee goes to the Espar, 2nd tee comes back from the Espar.

Do you have a manual with it? Where did you get your Espar from?

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

I got the Espar from a friend who never used it and I downloaded the manual from Espars website.

Would that really work? Wouldn't I need to tap both the line TO the heater core with and the line FROM the heater core. That way the coolant would circulate around the block and not just in the heater core hose. I think these hoses are different sizes also. It looks like the hose to the heater core is 3/4" while the hose coming back to the block is maybe 3/8".

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1987 300SDL-268k mi

For that to work you will need a check valve in the heater hose between the tees.

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Gone to the dark side

- Jeff

Yes, that is how I have seen the Webastos. They have a check valve inbetween the two tees. If you have a manual, install it like they show.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

A check valve in parallel with the heater would definately work.

I was just reading up on these things yesterday. I was looking a the Diesel version of the Espar 4. In low speed it is rated at 2,400 watts per hour. That is about 5 times more heat than the block heater puts out. And it does it using a tiny amount of fuel, something like 100mL of Diesel per hour. That would really do the trick at the end of a 10+ hour work day sitting out in the cold parking lot.

I wonder how well it works with biodiesel?

-Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.

No, the block heater heats the coolant jacket around the cylinders.