2000 Chevrolet Blazer - Rear Main Seal Set

Shop Replacement Rear Crankshaft Seal Sets

A vehicle's rear main seal, also known as the rear crankshaft seal, is located inside the rear of the engine where the crankshaft exits the engine block. A rear main seal's purpose is to keep engine oil from leaking around the crankshaft as it rotates, which can cause low engine levels and damage to the starter motor. Rear main seals can be made of rubber or silicone and may be a single-piece seal or a two-piece seal that might require the crankshaft to be removed to replace. The rear main seal can wear out over time due to the rotational forces of the crankshaft, corrosion, low oil levels, and other environmental factors. Vehicles that sit for long periods of time without running also risk the rear main seal drying out and tearing on startup. If your rear main seal is damaged and needs to be replaced, oil leaks near the rear of the engine or the front of the transmission will be the most obvious sign of an issue. Signs of a bad rear main seal include an illuminated low oil pressure light, oil residue on the rear of the engine, or oil puddles forming under the transmission bell housing, and in the case of oil contamination on your starter, failure of the engine to start when you turn the key. If you remove the starter and it is noticeably oily where it enters the transmission bell housing, this could be due to a rear main seal or transmission pump seal leak. If you hear a ticking or a clicking noise, this could also indicate low oil levels that could quickly lead to catastrophic engine failure. It's also important to note that oil leaks can be caused by other seals or gaskets failing, so be sure to inspect parts like the oil pan gasket and valve cover gasket to correctly identify the source of the oil. If you notice liquid around or beneath your engine or vehicle but aren't sure what it is, read our article to learn what's leaking from your vehicle. Driving with an oil leak is not recommended or ideal, but the speed of the oil leak can tell you the level of urgency. O'Reilly Auto Parts carries rear main seals, motor oil, funnels, shop towels, and more to help you make a complete repair and prevent damage to your vehicle's engine.