Water Heaters - Why wont it work?

I have a Kenmore 30 gallon single element (3800 watt) 240 volt electric hot water heater. It recently quit working so I checked the breaker then tried the reset button and it didnt help so checked for power to the tank then at the thermostat then at the element and it had power all the way to the element. I replaced the element, filled it and flipped it on and it still didnt work. So I figured maybe I had gotten a defective element and got another new one, this time the hardware store didnt have any 3800 watt elements so I got a 4500 watt element and put it in. It still has power (120 volts each side) all the way to the element (checked with a multimeter from the ground wire to each side of the element) but still dosnt work. Can anyone let me know what is likely the problem with it? I though if you had a good element and power to it that it would heat the water? The ground I tested to was the screw that holds the ground wire to the outside of the tank. Could it still be a problem with the ground somewhere? If so where would be likely?
Thanks in advance for any help.

Check to see if you have 240 volts across the element terminals. The ground is only used for safety, not for normal operation. I suspect you do not have 240v at the element.

Make sure you have 240 volts going to the power connections at the heater.
If you do, then you probably have a bad thermostat.

Whoever installed it osed romex that just has the 2 insulated wires and 1 bare wire and used it as a 240 line with the 2 insulated wires for the hot and the bare as the neutral. I reconected the new elements the same way the old one was hooked up (it had worked for the 3 years we have been here) but it wont work now. If the thermostat were bad wouldnt it prevent power from getting to the element?

Your wiring sounds correct; L1,L2 and ground. 240 volt water heaters don't use or need a neutral.

L1 and L2 are 180 degrees out of phase with each other. Each will measure 120v to ground, but will measure 240 volts when measured to each other. Your water heater thermostat shuts off only one side of the line. Again, measure the voltage at the heater element, not the ground. You should have 240 volts with or without a burned out element. If not, your problem is with your breaker, wiring or your thermostat.

Jim, your last post finaly gave me the tid bit I needed to figure it out! I was thinking in terms of DC, with positive and Negative rather than AC with L1, L2 and neutral so was thinking of both hot wires as being pos and that being why I wasnt getting a reading across the 2 posts of the thermostat. It was reading 120 from iether side to the ground but nothing across it, so I checked again in the box and it had 120 on one leg and only like 20 on the other. Turns out the burried line from the pole to the house had gotten a hole in the insulation and oxidized to powder. I got a couple of clamps and spliced past the problem (a temporary fix ONLY untill I can get some place that has the wire and a bit of cash to pay for it) and wrapped a roll of electric tape over it, now the water heater is working and so is the electric dryer that had not been heating for some time but thought that was its element since it still tumbled.
So the problem is now found and a bandaid is on it to fix it untill we can fix it right. Thanks for all those who replied and especialy for the last info on how to test it that gave me the info I wasnt thinking of to find the problem.