Rear Main Seal Replacement Tips
By Chris Fasulo and Mike Smith
You Will Need
A good time to do the rear main seal is during an oil change as you have to drain the oil anyway. You'll also want to set aside several hours for this job as it is a good idea A) to make sure everything is clean and B) to give the RTV sealer used in the main cap side cavities time to cure. Despite the numerous steps below, the job is not hard to do if you just take your time. All attempts have been made include everything needed.

Stuff you'll need...............

  1. New Neoprene rear main seal
  2. Black or Ultra-Black, O2 sensor safe RTV Sealer
  3. New Oil Pan Gasket
  4. Breaker Bar

Tools you'll need................

  1. 1/2" drive ratchet, 5/8" socket for rear main cap bolts use a 6-point socket on rear main cap bolts!!!
  2. 1/4" drive ratchet, 1/2" & 7/16" socket for oil pan bolts
  3. Torque wrench (1/2" drive, 0 to 150 lb/ft min)
  4. Needle Nose pliers
  5. Rubber Mallet or "soft" hammer
  6. Rags & Acetone to clean surfaces
  7. Small screwdriver and/or putty knife to clean off old RTV sealer

Stuff you may need...........

  1. New oil screen pick up gasket
  2. Piece of stiff sold copper wire--plastic coated is O.K.
  1. Drain Oil, remove crossover pipe and oil pan. Depending on you car, you may or may not need to lift one side of the engine to get the pan off. Some guys have used their engine tie down to rock the engine over to one side. If you do need to jack up the engine use a block of wood (piece of 2x4) between the engine and the jack. Locate the jack at the front of the transmission pan. The three bolts at the front of the pan are smaller (10mm) than all the others. There is one bolt on the passenger side that secures a clamp that holds the tranny lines. This one can be a real pain to get off (try using an open end wrench.) There is a baffle in the oil pan and it can hang up on the oil pickup screen. If you have trouble removing the pan, try rotating the engine to get the counterweights out of the way. Removal of the converter dust shield may also provide more clearance. As a last resort, removing the pickup tube guarantees that the pan will come off.

  2. Inspect the oil pickup screen. You may find your old rear main seal on the bottom of the screen!!! *IF* the screen looks like it needs cleaning or is all clogged up, remove it and clean it. REPLACE the gasket that goes between the block and pick up. Apply loctite thread sealer to the oil pump pickup bolts. These bolts are prone to working lose. If they do, you will lose oil pressure and your engine soon after!!! Factory torque spec is 96 inch/lbs (or 8 ft/lbs.)

  3. The torque spec for the rear main cap bolts is 100 lb/ft. It is helpful to have a breaker bar to get these bolts loose. Once loose, the bearing cap is more than likely going to stay "stuck" in place. The side cavities of the cap are filled with RTV sealer. One trick is to loosen both main cap bolts completely and pull them about 1/2 way out of the cap. You can then use them as "handles" to wiggle the cap front to back to get it loose. You may also need to pry against the crank flange and the back side of the cap to get it loose. Keep working at it...that old RTV can be tough to break loose! You can also run a very small screwdriver up the cavities to break loose the RTV. DO NOT DROP THE CAP! The lower half of you rear MAIN BEARING will be in the cap. Don't get any dirt on the bearing. The crankshaft journal will also be exposed with the cap off. Take care not to nick or scratch it-- there should be no need to even touch it.

  4. Move the main cap to a work bench. The lower half of the main seal can be pulled out by hand or with a pair of needle nose pliers. ALL of the old RTV sealer needs to be removed from the side cavities and sides of the main cap. Lube one half of the new main seal and slide it into the groove in the main cap. The split part of the lip on the new seal faces the front of the engine. The package should show the correct orientation of the seal lip. Set the cap aside (covered to eliminate the possibility of airborne particles falling on it.)

  5. Again, depending on the car, the upper half of the main seal may be easy or difficult to remove. Remember, your working around your crank journal so be careful. Try and grab the main seal with a pair of needle nose pliers and pull it out. If it comes out in one piece you're all set. If it breaks, you may need to gently slide a piece of stiff insulated solid copper wire up in to push the remaining piece(s) of seal out. Sometimes it helps to have someone turn the engine while you push on the seal to remove it.

  6. Once the old seal is out, clean off any RTV sealer on the block. Lube up the other half of the new seal and slide it up into the block with your thumb--make sure it is facing the right way!

    Note: One trick is to insert the new seal so that the mating faces of the new seal are not lined up with the mating faces of the main cap. About a 1/4" extra rotation one way is enough.

  7. Put a thin coat of RTV sealer on the cap-to-block mating surface of the main cap and on the chamfered edge. Lube the main bearing with clean oil. Make sure the bearing is seated in the cap. If needed push the bearing into the cap and make sure the tang is engaged in the slot in the cap. Install the cap back in the block. You'll be able to push it up about 95% of the way by hand. Then tap on the bottom of the cap with a rubber mallet to get the cap seated back onto the block. Install the main cap bolts and torque them to 25, 50, 75, then 100 lb/ft--or you can just set your torque wrench to 100 lb/ft and turn the bolts a 1/2 turn or so at a time till you reach 100.

  8. The side cavities need to be filled full of RTV sealer. This can be as much fun as getting the pan off! RTV has a viscosity of about 200 weight! (Do not use the rubber inserts that come with the new seal; just use RTV sealer.) Make sure you start with a new tube of sealer. Cut the tube so it will fit into the side cavities (one notch down on a new cone tip.) One trick is to slide a flat washer over the tube tip and use it to have something to push against as you squeeze the cavities full. Stick the tip in and squeeze away! Keep filling the cavities until you see it squirt out the sides of the main cap. Stick a piece of wet wire into the cavities and remove. This is done to break any air pockets and provide the moisture needed to cure the RTV.

  9. Reinstall oil pan and crossover pipe. Apply a smear coat of RTV to the seams where the main cap meets the bottom of the block--where the oil pan bolts on. You can also put a smear coat where the front cover mates to the block. If your using a rubber (stock) oil pan gasket it is going to be tricky getting the pan up and in place without the gasket moving all over the place! If you can get a cork gasket you'll be better off! Don't be afraid to use a few dabs (just don't use globs!) of RTV to stick the gasket to the pan. Install all oil pan bolts loosely (to make sure they all go in straight) and then tighten to 96 inch/lbs (or 8 ft/lbs.)

  10. Fill her up with oil and a fresh filter. If you removed the oil pick up screen, disconnect the power to the computer and crank the engine over to make sure you are getting oil pressure. (If you are having trouble building oil pressure, remove the spark plugs and turn over the motor. It will spin much faster without the compression load dragging it down.) Start the engine and keep an eye out for leaks for the next few days.

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