How do u remove the lower thermistat from model #E2F40LD045V

Agreed. If you have a meter, or know someone who has one (and knows how to use it), you could narrow it down as to which element is bad.

follow this steps and use the Voltmeter, and fix it. God bless you
oubleshoot a thermostat:

1. Shut off power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Unscrew and remove the electric water heater access panel.
3. Using a small screwdriver, turn the thermostat dial counterclockwise to lower the temperature, or clockwise to raise it. If the water heater doesn't maintain the proper temperature, test the thermostat.
4. Disconnect one wire to the upper thermostat to test it. Set a multimeter to RX1 (resistance times 1) and touch a probe to the thermostat terminals as indicated in the owner's manual. Depending on the model and the terminals tested, the tester should show infinity ( open) or about 0 ( closed).
5. Test the lower thermostat in the same manner.
6. If necessary, replace the thermostat. Unscrew it from its mounting and install one of the same model, size, and rating. Once you install it, adjust the thermostat following instructions in your owner's manual.

Test and replace a heating element:

1. Turn off power at the electric panel and post a sign warning others not to turn it on.
   
2. Remove the access panel on the electric water heater.
   
3. Disconnect one of the element wires and set a multimeter to RX1000 (resistance times 1,000). Touch one probe to an element mounting bolt and the other to each element terminal screw, in turn. If the tester displays anything but infinity ( open circuit), replace the element.
   
4. If necessary, set the multimeter to RX1 and touch the probes to the terminal screws. If there is any resistance reading at all ( closed circuit), then the element is good. If not, replace it. Both upper and lower elements are tested in the same manner.
   
5. To remove the element, first drain the heater.
   
6. Disconnect the remaining element wire. Remove the mounting bolts holding the element in place. Remove the element.
   
7. Replace the heating element with one of the same model, shape, and rating. Make sure you also replace any installation gaskets.
   

Test and replace a high-limit cutoff:

1. Disconnect power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Remove the upper access panel and push the reset button.
3. Replace the access panel and turn the power back on. If the water is hot, the reset was the problem. If not, you'll need to turn the power off again and reopen the access panel.
4. Use a multimeter to test the cutoff terminals for continuity. If faulty, replace with an exact replacement part.

Some elements is in Short circuit, test the procedure before

some elemente is in short circuit. test the follow steps and fix it. God bless you
oubleshoot a thermostat:

1. Shut off power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Unscrew and remove the electric water heater access panel.
3. Using a small screwdriver, turn the thermostat dial counterclockwise to lower the temperature, or clockwise to raise it. If the water heater doesn't maintain the proper temperature, test the thermostat.
4. Disconnect one wire to the upper thermostat to test it. Set a multimeter to RX1 (resistance times 1) and touch a probe to the thermostat terminals as indicated in the owner's manual. Depending on the model and the terminals tested, the tester should show infinity ( open) or about 0 ( closed).
5. Test the lower thermostat in the same manner.
6. If necessary, replace the thermostat. Unscrew it from its mounting and install one of the same model, size, and rating. Once you install it, adjust the thermostat following instructions in your owner's manual.

Test and replace a heating element:

1. Turn off power at the electric panel and post a sign warning others not to turn it on.
   
2. Remove the access panel on the electric water heater.
   
3. Disconnect one of the element wires and set a multimeter to RX1000 (resistance times 1,000). Touch one probe to an element mounting bolt and the other to each element terminal screw, in turn. If the tester displays anything but infinity ( open circuit), replace the element.
   
4. If necessary, set the multimeter to RX1 and touch the probes to the terminal screws. If there is any resistance reading at all ( closed circuit), then the element is good. If not, replace it. Both upper and lower elements are tested in the same manner.
   
5. To remove the element, first drain the heater.
   
6. Disconnect the remaining element wire. Remove the mounting bolts holding the element in place. Remove the element.
   
7. Replace the heating element with one of the same model, shape, and rating. Make sure you also replace any installation gaskets.
   

Test and replace a high-limit cutoff:

1. Disconnect power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Remove the upper access panel and push the reset button.
3. Replace the access panel and turn the power back on. If the water is hot, the reset was the problem. If not, you'll need to turn the power off again and reopen the access panel.
4. Use a multimeter to test the cutoff terminals for continuity. If faulty, replace with an exact replacement part.

follow this steps and fix it. God bless you

oubleshoot a thermostat:

1. Shut off power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Unscrew and remove the electric water heater access panel.
3. Using a small screwdriver, turn the thermostat dial counterclockwise to lower the temperature, or clockwise to raise it. If the water heater doesn't maintain the proper temperature, test the thermostat.
4. Disconnect one wire to the upper thermostat to test it. Set a multimeter to RX1 (resistance times 1) and touch a probe to the thermostat terminals as indicated in the owner's manual. Depending on the model and the terminals tested, the tester should show infinity ( open) or about 0 ( closed).
5. Test the lower thermostat in the same manner.
6. If necessary, replace the thermostat. Unscrew it from its mounting and install one of the same model, size, and rating. Once you install it, adjust the thermostat following instructions in your owner's manual.

Test and replace a heating element:

1. Turn off power at the electric panel and post a sign warning others not to turn it on.
   
2. Remove the access panel on the electric water heater.
   
3. Disconnect one of the element wires and set a multimeter to RX1000 (resistance times 1,000). Touch one probe to an element mounting bolt and the other to each element terminal screw, in turn. If the tester displays anything but infinity ( open circuit), replace the element.
   
4. If necessary, set the multimeter to RX1 and touch the probes to the terminal screws. If there is any resistance reading at all ( closed circuit), then the element is good. If not, replace it. Both upper and lower elements are tested in the same manner.
   
5. To remove the element, first drain the heater.
   
6. Disconnect the remaining element wire. Remove the mounting bolts holding the element in place. Remove the element.
   
7. Replace the heating element with one of the same model, shape, and rating. Make sure you also replace any installation gaskets.
   

Test and replace a high-limit cutoff:

1. Disconnect power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Remove the upper access panel and push the reset button.
3. Replace the access panel and turn the power back on. If the water is hot, the reset was the problem. If not, you'll need to turn the power off again and reopen the access panel.
4. Use a multimeter to test the cutoff terminals for continuity. If faulty, replace with an exact replacement part.

follow this steps and fix it. God bless you

Troubleshoot a thermostat:

1. Shut off power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Unscrew and remove the electric water heater access panel.
3. Using a small screwdriver, turn the thermostat dial counterclockwise to lower the temperature, or clockwise to raise it. If the water heater doesn't maintain the proper temperature, test the thermostat.
4. Disconnect one wire to the upper thermostat to test it. Set a multimeter to RX1 (resistance times 1) and touch a probe to the thermostat terminals as indicated in the owner's manual. Depending on the model and the terminals tested, the tester should show infinity ( open) or about 0 ( closed).
5. Test the lower thermostat in the same manner.
6. If necessary, replace the thermostat. Unscrew it from its mounting and install one of the same model, size, and rating. Once you install it, adjust the thermostat following instructions in your owner's manual.

Test and replace a heating element:

1. Turn off power at the electric panel and post a sign warning others not to turn it on.
   
2. Remove the access panel on the electric water heater.
   
3. Disconnect one of the element wires and set a multimeter to RX1000 (resistance times 1,000). Touch one probe to an element mounting bolt and the other to each element terminal screw, in turn. If the tester displays anything but infinity ( open circuit), replace the element.
   
4. If necessary, set the multimeter to RX1 and touch the probes to the terminal screws. If there is any resistance reading at all ( closed circuit), then the element is good. If not, replace it. Both upper and lower elements are tested in the same manner.
   
5. To remove the element, first drain the heater.
   
6. Disconnect the remaining element wire. Remove the mounting bolts holding the element in place. Remove the element.
   
7. Replace the heating element with one of the same model, shape, and rating. Make sure you also replace any installation gaskets.
   

Test and replace a high-limit cutoff:

1. Disconnect power to the heater at the electric panel and post a sign warning others not to turn it on.
2. Remove the upper access panel and push the reset button.
3. Replace the access panel and turn the power back on. If the water is hot, the reset was the problem. If not, you'll need to turn the power off again and reopen the access panel.
4. Use a multimeter to test the cutoff terminals for continuity. If faulty, replace with an exact replacement part.

Question posted under marathon electric water heater.
Marathon is 240Volt dual element non-simultaneous water heater.
Non-simultaneous means that upper part of tank has to reach temperature before power is sent to lower thermostat and element. So if upper element is bad, then water heater has no hot water.
http://waterheatertimer.org/Replace-anode-rod.html#audibleBW

1) You need to by-pass upper element without by-passing upper thermostat.
2) You should never by-pass upper thermostat because it has ECO-reset protection.
http://waterheatertimer.org/How-water-heater-thermostats-work.html

3) Open following link for image of wiring:
http://waterheatertimer.org/images/Marathon-wiring-700.jpg
4) Take photo of your wiring in case color code is different on your specific model

5) Look at upper thermostat.
Remove yellow wire from terminal 2 on upper thermostat, and cap off temporarily.
Remove red wire from terminal 4 on upper thermostat, and move it to terminal 2 on upper thermostat.
6) For more effective operation, look at lower thermostat.
Remove black wire from lower thermostat terminal 1 and move wire to terminal 2 on lower thermostat.

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Sounds like the new thermostat and ECO you installed, You may have got them mixed up. The ECO will have a small reset push button in between the 2 spade connectors. The ECO should be second in line, as in power to it comes from the thermostat. Hot (black) line from switch goes to thermostat first, then from opposite spade on thermostat to spade on ECO, then out from ECO to element. Double check wiring or positioning of thermostat and ECO, and correct as needed, and make sure to push reset in center of ECO, then try again. Be sure both are touching up against tank well too.
The thermostat has a little lower temperature setting, and if it fails, ECO takes over and cuts out at a little higher temperature. That's why I suspect they got mixed up, otherwise thermostat (without reset) should have cut power at proper temperature, unless it's faulty, or not touching against tank properly.

Let me know how you make out and what you found.

Residential water heaters USUALLY follow same diagram unless water heater is wired for other purpose. Multiple diagrams on instructions show available options. Take photo of wiring before removing wires on any electrical device.
Upper element.
Black wire from top of heater connects to #1 top left screw.
Red wire from top connects to #3 top right screw.
Blue wire from upper element connects to #4 middle screw on right side
Red wire from lower element connects to #4 middle screw on right side
Yellow wire from upper element connects to #2 lower left screw
Black wire from lower thermostat connects to #4 lower right screw
Upper element: Yellow and Blue wires connect to either screw
Lower element: Red wire from top connects to either screw
Lower thermostat: Black wire from top connects to top screw
Short wire between lower thermostat and lower element

http://waterheatertimer.org/images/Water-heater-wiring-w-numbe.jpg
http://waterheatertimer.org/images/Thermostats-numbered-divided-500.jpg
http://waterheatertimer.org/How-to-wire-water-heater-thermostats.html

You need to check the electric elements they are under removable covers on the front of the heater and check the fuse/breaker. May need to replace upper and lower elelments

Is this water heater gas or electric?If its electic then maybe the breaker is not turn on.If it gas then you will have to lite it if ti's not automactic.Tell me more if you can and I will see if I can help you better.
Thanks