Oil leaking

You need someone to look at it to see what is causing the leak. They will give you an estimate for the repairs. There's no way I can tell what is wrong over a computer.

I took it to the Mechanic and he said needs to change the seal . I want to know how much is charging for this problem? Thanks

There's a dozen seals and gaskets. Some are real easy to replace. Some are very difficult. Your mechanic is the one to tell you what the repairs will cost.