Not too long ago I noticed that my car was a lot noiser in the cold morning air than it had been, I also noticed a drop in mileage. I've taken my car to an exhaust place and they have located a leak at the exhaust manifold (where it hits the block). The leak apparently isn't very large because as all the parts get hot it seals back up. The guy at the shop didn't think the exhaust leak would cause the mileage drop I've seen (approx. 5 mpg) and has suggested replacing the O2 sensor and the exhaust manifold gasket. I'm ok replacing the O2 sensor myself, that'* pretty straight forward, but I'm not sure about tackling the exhaust manifold gasket though. What'* involved in doing it? Can a "shadetree" mechanic do it using handtools and a jackstands? He ballparked a price for me of about $275 but set the expectation that it'd most likely end up being more around $200-225. I've never tackled one of these, so I'm looking for opinions. How much of a PITA is it to change one of these?

Thanks

I should also mention that the leak is at the back manifold, not the front one.

the rear manifold is nearly impossible to gat at without a lift, i still have my rear PEM in my trunk because its such a pain in the *** to do

Having seen Toasty'* car and the idea of a back manifold. It looks like the procedure would be to drop the exhaust and push it aside. Then you have that space to work in. A lift would be a big help.

the way i see to be the easiest is to take down the exhaust, then unbot the engine/tranny cradle, and rock the whole thing down in the rear in order to get much clearance. you have to fight with the downpipe, powersteering rack, engine cradle, and transmission all being in your way. it sucks.

Ahem..Toasty..if the exhaust is pulled..... the down pipe isn't there.

I'm going to be replacing the O2 sensor in my car sometime soon, the parts slated to be delivered on Monday. Would doing this before getting the exhaust leak fixed harm the sensor in any way? I'm asking because I'm wanting to get some PEM'* or Headers (probably early next year) and the labor to have those installed is only a little more than just fixing the leak. It'* a small leak that seems to fix itself once the engine warms up so I'm willing to live with it for a while so long as it doesn't damage anything else.

If the leak is minor it shouldn't harm the sensor. To be safe...maybe wait on the sensor unless you are having issues.

My gas mileage is BAD...I did the math and I'm averaging 18 MPG with about 80% of my driving being highway driving. The DIC this morning showed that I was getting 7 mpg on the on ramp this morning, and that wasn't under hard acceleration or anything.

Yikes....Not horrible mileage, not great either though.