By March 20, 2007 Read More →

Oil Leak in Rear Main Seal

Reader question:


I have a Honda with a D16A9 engine. I recently had problems with a noise in the gearbox, and took it in to be repaired. What was going to be just a replacement of a bearing, turned out to be a complete gearbox overhaul (Very expensive!). As part of this they also replaced the rear main seal.

When I got the car back, the rear main seal was leaking engine oil. It never leaked before, so I took it back. After they installed two more seals, they are saying that there is “a groove in the crank shaft”, and for this reason, the new seal will leak oil, even though the old seal didn’t.

This sounds a little bit suspicious to me, especially since I really really don’t have money to spare at the moment, and this is also very expensive to fix. I do get the feeling that I am being cheated, but to investigate something like this would cost me even more money.

This is an old engine, it’s done about 300,000 km. But it is running smoothly, and I was hoping that it would last quite a bit longer.

So the question in a nutshell: Could it be that the crank shaft is damaged or “grooved” in such a way that the old seal was not leaking any oil, but the new seal does?

Thank you so much for your very handy website!!


Hey there Louis,

It COULD be possible for the old seal not to leak, because it had these grooves slowly cut into the old seal, and the grooves on the crankshaft matched the grooves on the old seal so little or no oil leaked out. That COULD be possible, probably extremely rare, but possible. I have seen crankshafts get a small burr on the end of them and I had to file off the burr so it would not tear the new seal I was about to install. A small piece of sand paper or emery cloth can help remove the burr and make the shaft smooth again.

What really comes to my mind here is they probably used an aftermarket seal and not a genuine Honda seal. Granted, there are only a few large seal manufacturers, and chances are one of them makes the seals for Honda, I am not sure if Honda makes their own seals or not. BUT, I have seen many times, an aftermarket seal that would not fit the whole and would leak and a genuine seal from the manufacturer DID seal the leak.

When ever I do a rear main seal or a timing cover seal job (jobs that require a ton of labor to get to) I ALWAYS use a genuine manufacturer seal. I have had to redo a few seal jobs before and I have learned my lesson. Seals are cheap, but the labor will eat you alive.

So, with that said, I would ask them to show you the seal they installed twice and it leaked. Maybe even ask them for the invoice for the part they bought, just to see if its an aftermarket seal or genuine Honda. If not genuine, I would buy one for them and have them install it. Once they get to where you can see and feel this supposed groove on the crank, tell them to call you so you can personally see if for yourself.

Austin Davis

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."

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