Oil Leak 351w

351W leak - Club Cobra

The rear main seal is leaking on my engine. I have had several people say the seal is a two piece part and is easy to change. I have had others say the engine and tranny have to be pulled to change the seal. Is it the age of the block that determines what needs to be done? Are all 351W blocks the same regardless of age? Help, I am a little confused! 6. Rear main seal- if two piece type- three likely causes, 1.ends of seals should be staggered in relation to cap parting line. 2. pin or hole for use with 'dogs turd' type rear seals, if this pin is not removed or the hole for it not filled & deburred it will distort the lower seal half at this point. 3. check that drain hole in rear main cap is open, I have seen some come from factory where they have not been opened up enough by the machine work which floods the rear seal. You can easily rule out some of the causes for a leak in the rear of the motor. First, if the rear cork seal of the intake is leaking there will be evidence of oil on the upper rear surface of the block directly below the intake manifold, easy to feel with your finger. If the oil pan gasket is the source, usually there will be oil present on the rear of the oil pan in front of the block plate. A flashlight will help here. If the leak looks like it is coming from inside the bell housing or mainly on the block plate, then it could be the main seal or the flywheel bolts but many times if the flywheel bolts are the source you will have oil on the surface of the flywheel and clutch problems as a result. Early blocks use a two-piece seal while late blocks use a one-piece seal. Usually it is the two-piece seal that gives the problems. When replacing the two-piece seal, be sure NOT to align the ends of the seal with the joint made by the end cap and the block. The ends of the seal should be offset. To replace the two-piece seal you must remove the tranny to get the input shaft out of the way and then drop the oil pan. Then the main caps need to be loosened to allow the crank to drop down a little. There is a tool available to make removing and inserting the new upper half of the seal easier. The job is easier than it sounds but it can be time consuming. The engine leak that appeared to be a rear main seal ended up being a leak where the remote oil filter adaptor attaches to the block! All the oil did run to the back and bottom of the engine.

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