as many as you have, as many as you have,
Depends on the nature of the problem. If the grid lines are broken you can get a repair kit that you basically paint on after you mask it off with tape.
You need to go to a car parts store, and get a repair manual for your car. They cost about $16.00 Or, go to a Public Library.
New Water heater. Faucet and sink drain line repair parts. The sinks, commodes, house and yard water supply lines. Sewer lines
Copper Tubing works very well with rubber connections just @ the motor & heater core.
The rear defroster (demister) on a Subaru Legacy is built into the window. The lines going across the back window are actually the defrosters. If the vehicle is equipped with a rear wiper, the switch for this should be located below the radio and heater controls.
An oil cooler extends the life of an engine by specifically keeping the oil 'cooler' that what the regular cooling system can do (which is designed to cool the entire engine). If your car has some SEEPAGE around the cooler and/or lines that is not the end of the world; but if it LEAKS repair it. Since it is external to the engine I would not expect it to be a major repair.
faulty control valve on heater or air in the lines
It should unless the lines are cut or damaged.
Begin by removing the water supply lines from your Nissan heater core. Remove the heater core retaining bolts. The heater core will come out.
how to remove the lines from the heater core on a 2001 expedition
Yes the lines can leak when they rust through.
Disconnect the send and return lines from the heater core and use a hose coupling and hose clamps to connect these two lines together