How to Rebuild a Wrangler Engine

Heavy off-road use requires a well built engine.

From 1987 to the present, AMC and later Chrysler used four different engines in the Jeep Wrangler. A 2.5 liter four cylinder, a 4.2 liter and 4.0 liter six cylinder, and a 3.6 liter V6 were all used at different times during the Wrangler's production runs. Rebuilding these engines require access to specialized equipment and machine shops.

Things You'll Need

• Engine hoist
• Wrench set
• Engine stand
• Jeep Service Manual
• Screwdriver set
• Torque wrench

Instructions

Removing the engine

1. Prep the Jeep. Depressurize the fuel system, disconnect the negative cable from the battery, remove the fenders and cowl. Drain the cooling system

2. Prep the engine. Remove the air cleaner assembly, label all vacuum lines, emissions hoses, and electrical connectors. Detach each item after labeling. Remove the cooling shroud and cooling system hoses. Remove the drivebelts.

3. Remove exterior engine components. Disconnect the throttle linkage. For 2007 and later models disconnect the large ETC connector at the the throttle body. Unbolt and remove: the power steering pump, starter motor, alternator, and air conditioner compressor. Drain the engine oil and remove the oil filter.

4. Unbolt the exhaust system and support the transmission. If the Jeep is an automatic, unbolt the torque converter and remove the structural lower bell housing cover.

5. Remove the engine. Wrap an engine sling around the engine. Unbolt the engine from the transmission and from the frame. Use the engine hoist to slowly move the engine forward and away from the transmission. Lift the engine up and out of the vehicle. Once out of the Jeep, remove the flywheel and mount the engine to the engine stand.

Items to rebuild or replace on the Jeep engine

1. Replace or rebuild the cylinder heads. Aftermarket cylinder heads can be swapped in for the original heads. An existing head can be ported and polished and the roller rocker assembly upgraded. New valves increase performance and efficiency.

2. Repair or replace the piston assembly. Replace worn rings, pistons and connecting rods. Hone the cylinder walls to restore smoothness. The cylinders may also be bored out to increase the displacement of the engine. This requires piston replacement.

3. Repair or replace the crankshaft assembly. If the engine had a knock on the lower end while running, the main bearings or the the connecting rod bearings may be worn. Replace worn main bearings. Take the crankshaft to an automotive machine shop to re-true it.

4. Replace the camshaft. Many companies supply aftermarket camshafts for different performance results. Jeeps used for climbing hills or heavy duty rock crawling need a camshaft that provides more low end torque. Jeeps intended primarily for street use need a camshaft that provides high end torque.

5. Clean and reassemble the engine. While the engine is out and disassembled it is an ideal time to clean out the engine. Flush oil and water passages out. Replace the freeze plugs. In some cases, take the engine to an automotive shop to steam clean or hot tank the engine. Reassemble the engine according to Chryslers Jeep Service manual or a Chilton's or Hayne's Jeep Repair manual. These manuals provide a guide for the correct clearances for all engine parts and torque specifications.

References

• Jeep.com: History
• "Haynes Repair Manual: Jeep Wrangler 1987 thru 2008"; Mike Stubblefield and John Haynes; 2009