Rear Main Seal Leaks (Part 2)

 

Rear Main Seal Leaks (Part 2)

 

 

As promised in the last issue, this will explain how to replace the rear main seal on a classic ('59-'85) Chevy V8, and also how to remove the oil pan with engine in the car (Chevelle small block automatic only). If you have a big block or manual trans, the trans and bellhousing must be separated from the engine and the rear of the engine lifted (big block) as well as the front, in addition to the following:


First, to remove the pan, disconnect the battery and remove the distributor cap and radiator top panel. Jack up the front of the car and support the frame on jack stands. Drain the oil, remove the oil filter and dipstick , and drop the exhaust pipes from the manifolds (or unbolt headers from pipes). Remove the flywheel dust shield and remove the fuel pump and plug the fuel lines. Rotate the crankshaft so the timing mark on the balancer is in the 6 o'clock (very bottom) position. Disconnect the starter brace, remove the inboard starter mounting bolt, and loosen the outboard bolt. Put a block of wood (a 4"x4" about 8" long works well) vertically on a floor jack under the balancer. Remove the "through" bolts from both engine mounts. Loosen the trans mount bolts at the crossmember. Jack the front of the engine up until 3" blocks of wood can be placed between the frame mounts and engine mounts. Pivot the starter away from the oil pan and remove the pan bolts and oil pan. You may have to jack the front of the engine up a little higher to get the pan to clear the trans flex plate during removal. Reinstallation with a new gasket is a reversal of this procedure (tip: glue the new cork gasket to the pan and the rubber end seals to the block). Put a dab of RTV at the junctions of the gaskets and end seals. CAUTION: Be sure the engine is properly supported before putting your hands up between engine and frame, mounts, etc.


To replace the rear main seal (this also applies to big blocks), remove the oil pump with pickup and crankshaft rear main bearing cap. Remove the lower half of the seal from the bearing cap. Use a small piece of rigid plastic or wood to push on one end of the upper seal half to get it started around and out. Once it moves about 3/8" or so, grab the exposed end with pliers (be very careful not to touch the crankshaft) and pull it on out. Install the new lower seal half on the bearing cap. Note: Install both seal halves with the point of the "V" pointing toward the front of the engine. Lube both halves of the seal with clean oil and using the small plastic "shoehorn" that comes with the seal, push the upper half into place with a small piece of rigid plastic or wood. The "shoehorn" prevents the seal's small top side lip from being sheared off by the sharp edge of the block during installation. You may have to turn the crank to "walk" it into place. Clean the mating surfaces of both seal halves AND the bearing cap/block joint with brake cleaner or lacquer thinner. Put a light smear of RTV gasket sealer on the upper/lower seal mating surfaces AND the block/bearing cap mating surfaces. Install the bearing cap and torque the bolts to spec. Install the oil pump with pickup and torque to spec. Reinstall the pan and add oil and filter, etc.
Now you can start parking your Chevelle on your friend's new concrete driveway without fear

(as long as it doesn't have other leaks).