How to Install a Graphite Rope Rear Main Seal

Rear main seals serve a very important function on the automotive vehicle. A rope or "wick" seal is a woven fiber seal that surrounds the crankshaft journal at the rear of the engine. The rope seal prevents leakage from the oil pan out through the end of the rear crankshaft support bearing. It is mounted inside the rear main bearing cap, and the procedure for removing and replacing the seal can be quite costly. A competent DIY repair person can accomplish the task if he takes his time and uses some basic tools and special repair techniques.

Instructions

Place the vehicle in "Park" for an automatic, or in gear for a standard transmission. Set the emergency brake and raise the hood. Use a socket to disconnect the negative battery cable. Use a floor jack to lift the front of the vehicle and place two jack stands under the frame. Lift the rear of the vehicle and place two jack stands under the frame. Position a shop light under the oil pan area. Go to the engine compartment and use a socket and extension to remove the dip stick tube mounting bolt.

Slide under the vehicle and use a socket to remove the main cross member bolts, and lay them aside. If your truck is equipped with a typical splash pan, use a socket to remove the bolts and lay the pan aside. Place a drain pan under the oil pan, then remove the oil drain plug with a socket. Let the oil drain completely. Replace and tighten the oil drain plug with a socket. Use a pair of pliers to twist the oil filler tube back and forth then up out of its socket.

Remove all the oil pan bolts with a socket ratchet and extension, then use a screwdriver to pry the pan loose and pull it down out of the way. If you have insufficient clearance to pull the pan out, use a socket to loosen and remove the front motor mount bolts on both sides. Use the floor jack to lift the engine block up 4 or 5 inches, then place a wooden block between the top of the motor mount bracket and the engine block; pull the pan out.

Locate the main bearing cap bolts that hold the crankshaft in place. Use a breaker bar to loosen and remove the rear most bolts on the main bearing cap, then pry the rear bearing cap loose with a screwdriver. Loosen the the rest of the main bearing cap bolts, but leave them in place so the crankshaft will not drop. Use a pair of needle-nose pliers to remove the old (lower) seal from the main bearing. Discard it.

Wipe the rear bearing cap clean with a rag. Especially clean the seal groove. Install the new lower rear main seal in the bearing cap, pushing it down into the groove, using your thumbs. Use a razor blade to cut it slightly higher than flush,with the bearing cap. Smooth a dab of oil over the seal. Use needle-nose pliers to remove the old upper rear main seal from the engine journal. Push a part of a rag up through the opening and pull it down from the other end to clean the journal surface and the seal groove.

Dab some oil on new upper rear main seal then push it up through the groove opening until it exits the other side. Use a screwdriver to gently prod it up into the groove from both ends. Make sure you have it aligned with the proper end of the seal facing the front of the engine; refer to the seal installation instructions. Firmly push the seal into the groove. Use a razor blade to cut off any excess rope material, slightly higher than flush with the end of the journal surface.

Set the rear main bearing cap up against the journal and screw the bolts in by hand. Use a socket to tighten the bolts alternately, until the cap sits flush with the journal. Tighten the rest of the main bearing cap bolts with the socket, but only enough to snug them up against the journal. Refer to your owner's service manual for the proper torque in foot-pounds for the main bearing caps. Use a torque wrench to tighten the bolts to manufacturer's specifications.

Use the floor jack to lift the engine and remove the wood block. Replace the motor mount bolts and tighten them with a socket. Set the oil pan in place and screw all the oil pan bolts in by hand. Starting in the middle of the pan, screw the oil pan bolts in with a socket, fanning your way out toward the ends of the pan. Set the splash pan back in place, insert the bolts and tighten them with a socket.

Prop the cross member back into the position, replace the bolts and tighten them with a socket. Move to the engine compartment. Using downward and twisting motions, push the oil filler tube back into its socket, then replace and tighten the filler tube bracket bolt with a socket. Use the floor jack to lift the vehicle, one end at a time, and remove the jack stands. Remove the oil filler cap and replenish the crankcase with new oil. Check your service manual for the proper amount, subtracting one quart for the oil filter, which you did not remove.

Reconnect the negative battery cable. Start the engine and check for leaks with the shop light.