Honda K20C Rear Main Seal 91214-5A2-A01

Genuine Honda Rear Main Seal (91214-5A2-A01) - Modern K-Series

This is one of the cheapest parts in your engine and one of the most expensive to ignore. The rear main seal sits where the crankshaft exits the back of the block, and getting to it means the transmission comes out. So it's a few dollars in parts and a full day of labor, which is exactly why you replace it while you're already in there rather than after it starts weeping.

Replace It With Your Clutch. Every Time.

The most useful advice on this page. If the transmission is coming out for a clutch, a flywheel, a rear main seal is a matter of course, not a judgment call.

Here's the math. The seal costs almost nothing. Pulling the transmission costs you a weekend or a shop bill. If you button everything up with the original seal and it starts leaking six months later, you're doing the entire job over for a part you could have replaced in five minutes while the crank was staring at you.

Rubber hardens with age and heat cycling regardless of mileage, so a seal that looked fine going back together can start weeping shortly after. Nobody regrets replacing one. Plenty of people regret not.

How To Spot A Rear Main Leak

Look for oil around the bellhousing seam, where the transmission meets the block. A rear main leak typically shows as oil collecting at the bottom of the bellhousing, or dripping from the inspection cover if your car has one.

What makes it tricky is that a rear main leak looks a lot like a leaking oil pan gasket or a transmission input shaft seal, since gravity puts all three in roughly the same place. Clean the area thoroughly, run the car, and look again to find the actual source before you commit to pulling anything.

One thing worth knowing: a rear main leak bad enough to reach the clutch will contaminate the friction surface and cause slipping or chatter. If you're diagnosing a clutch that's misbehaving on a car with an oily bellhousing, you may be looking at the cause rather than a coincidence.

Use The Genuine Seal

Given what it costs to access, this is about as clear a case for the factory part as exists in your engine. The seal has to hold against a spinning crankshaft, through heat cycles, for years. A cheap seal that hardens early means doing the whole job again.

This is the exact part Honda spec'd, 91214-5A2-A01. On a job where the part is the smallest line item by a wide margin, buying anything else makes no sense.

Install It Carefully

Rear main seals are unforgiving of rough handling, so take your time.

Get the crankshaft sealing surface clean and inspect it for a wear groove where the old seal rode. Seat the new seal square rather than cocked, and use a proper installer or a driver that presses evenly across the face instead of hammering on one edge. And be careful not to nick or roll the sealing lip as it passes over the crank.

A seal that goes in slightly crooked or with a damaged lip will leak from day one, and you'll have done all that work for nothing.

Fitment

2016-2022 Acura ILX
2024-2026 Acura Integra Type S
2019-2025 Acura RDX
2015-2025 Acura TLX
2018-2022 Honda Accord 2.0T
2016-2021 Honda Civic LX / EX (2.0 NA)
2017-2021 Honda Civic Type R (FK8)
2022-2026 Honda Civic Type R (FL5)
2015-2019 Honda CR-V
2023-2026 Honda HR-V

Covers K20C variants including the K20C1, K20C2, K20C4, K20C6, and K20C8. Given the range this spans, it's worth confirming against your engine's parts diagram before ordering.

Who Should Grab One

This is for anyone with the transmission out for any reason, and for anyone who's found oil at the bellhousing and traced it here. It's the definition of cheap insurance: a few dollars now against a repeat of the most labor-intensive part of the job. If the crank is exposed, put a new seal on it.

Fits: modern Honda and Acura K-series, see the application list above. Part number: 91214-5A2-A01. Type: genuine Honda rear main seal. Recommended: replace whenever the transmission is removed.