Q: Would a good mechanic destinguish a valve cover leak from a timing cover gasket leak on 1995 Buick Regal

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I had large amounts of clean oil ending up on the ground very quickly. I was charged $750 by a dealership who felt I had 3 leaks: 2 valve cover leaks, oil filter adapter gasket housing and also claimed to find a leak in a trannie hose. Got the car home after paying the still a huge puddle of oil under my car. Now they want an additional $12000 to fix a timing cover gasket leak, $2000 total!!!??? should'nt that have been the first thing to eliminate. My prior authorization of $750 was based on the fact I thought i was taking care of every leak on a vehicle with 105,000. Miles. Now I am in a delima and feel I just threw my money away on a job done by an very sloppy incompetant mechanic( who I may add decided to do a dye test and pressure clean of the engine the second time around). My additional question also is, Has anyone ever seen a valve cover leak drip on the ground so bad that a mechanic would actually believed it was a major leak issue. Or was this another tactic to rip me off!I always thought they just smelled a lot and oil drips there just burned up on the manifold. I thnk a lot of people just live with the nuisance of valve cover leaks anyway, however timing gaskets are a different story My leaky car is still there, and I wrote a nasty letter to the owner of the dealership to see his response
(1) Answer
A valve cover gasket leak will not leak at the rate you are mentioning, you're correct. The oil filter adapter can however, and if the valve cover gaskets were leaking I would recommend them at the same time too.
However, when you have a big leak, and several leaks (possibly) it is important that you do what they did the second time and that means cleaning and adding dye. The mechanic was negligent in that they didn't properly diagnose the problem, I would say they were trying to rip you off, they just were lazy and didn't take the time to properly diagnose the problem.
You did the correct thing by sending the owner a letter, see what happens. You have other options too if they are non responsive, but give them an opportunity first to address the problem.