Replacing glow plugs in the Jeep Liberty's 2.8-litre diesel engine is similar to changing spark plugs except there is no firing order to worry about. The glow plugs thread into the cylinder head just below the intake manifold on your Liberty and have a single wire connected to the top, providing seven volts of electricity to the plug. The plug heats up the cylinders on your diesel engine to allow faster start-ups when the engine is cold.
Open the bonnet of your Liberty and locate the negative battery cable on the top of the battery. The battery sits on the driver's side of the engine compartment, right behind the driver's-side headlight assembly. Loosen the clamp bolt on the cable end with a wrench and remove the cable from the battery, isolating it from the terminals while you are working.
Locate the glow plug in question on the side of the cylinder head. The cylinder head is at the top of the engine assembly, running front to back along the engine block. Grasp the wire at the top of the glow plug at the boot and pull it straight off the plug. Lay the wire aside.
Place a socket over the glow plug, attach a ratchet, and turn the plug counterclockwise. Pull the plug out of the cylinder and discard it.
Carefully insert the new glow plug in the cylinder head. Tighten the glow plug to 110 inch-pounds with a torque wrench. Snap the wiring harness connector onto the top of the glow plug. Repeat the process for the remaining glow plugs until you have replaced all that are defective.
Install the negative battery cable on the negative battery terminal. Tighten the clamp bolt with a wrench, making sure it is secure. Do not over-tighten it or you may damage the cable end or terminal. Close the bonnet of your Jeep.