The project: Convert the mercedes benz 300D sedan to run on WVO (waste vegetable oil)
Stage 2: Tank heater.
Parts!
This is the heater that was designed to be inserted into the tank. Unfortunately this is not the final design as this one wouldn't quite fit. Fitting the copper U into the tank turned into an all day trial and error process. Ultimately, the tank heater ended up being approximately 14" deep and did not exdend as far into the tank as was desired, so I brazed a copper CPU heatsink brazed onto the bottom.
This might be re-done in the future, possibly by either using flexible steel hose designed for LP gas, or by getting another yertically mounted mercedes gas tank and installing it directly to the rear of the current one, wich an entire radiator sandwiched between them,
It was threaded into the fuel guage sender hole.. and was nearly impossible to get in, so once it was installed I didn't want to take it out just to have a picture.
The 3/8" copper "U" was threaded into the tank through the sender hole one end at a time. Then, two 1/2 holes were drilled into the top of the tank (under the first aid kit) and 3/8" compression fittings were JB Welded in place. The copper tube pokes up through the holes in the tank and then through the compression fittings. This was designed to prevent any coolant from leaking into the tank.
Next a 3/8" copper compression to 1/2" hose barb adapter was used for the lines going through the trunk and under the car.
The wire you can see poking out of the trunk is for the temperature sensor.
A $10 inside / outside temperature sensing unit was acquired. The external probe was installed in the engine compartment (at the moment it is taped to one of the fuel injector lines.) The unit also contained an internal temperature sensor. This sensor was taken out, attacked to a long wire, and JB-welded to a magnet and dropped into the fuel tank right near the fuel pickup.
Direct link to temperature sensor of similar quality from Harbor Freight. They only read up to 158 Degrees Fahrenheit. but for this purpose it will work just fine.