Issues with my 88 Towncar

Ok, since I'm not sure how many miles are actually on the car I have to guess it's at least 150,000mi. but could be 250,000 becuase the car was driven back and forth from Texas to Tenessee many times over the years. I know that engines wear over time so I was expecting something to break when I bought the car. Especially since the previous owners didn't exactly take care of it. There's just something about 97cent oil from wal-mart that doesn't fit with me...lol

Problem #1:

It appears the rear main seal is leaking. I foolishly tried some of the addtives and it made it worse. What type of money am I looking at for getting it replaced?

Problem #2:

When I first start the car, and especially if it has set for a few hours, there's a horrible knock for a about 2 or 3 seconds until the "OIL" light goes off. I can hear and feel it quite well. When the car's running you can hear a slight clatter coming from under the engine. What is causing all the knocking? Is my oil pump failing or is it just worn bearings? I thought about putting a manual oil gauge in there to check the pressure but I don't have time.

Now, in regards to problem #1, if I need anything replaced in the lower-end of the engine, having a mechanic do it all(problem 1&2) would probably cost me a buttload woudln't it? I could do that work myself if I could just get someone to pull and put back the engine when I'm done. I've worked on the lower-end before on other cars with my father.

This car runs excellent aside from the above issues and I'd hate to have the engine blow a rod while I'm on the highway. Surprisingly I'm still getting about 21mpg at 70mph with the a/c on. Your suggestions are definately appreciated. Thanks.

For the second problem, try using a higher grade gasoline. You don't need to go to a different gas station, but, use a higher octane rating. Also if that fails, change the oil. Use synthetic oil. I recomend Mobil 5000. Make sure it is FULL synthetic. It should say right on the bottle. If that fails, replace the piston shaft. It is probably not the piston shaft, but, anything is possible. If the noise started all of a sudden without you changing anything (gas etc), just change the oil like I said. Those are basically the only problems that cause knocking. If you do the oil change yourself, make sure you drain both parts of the resivoir. The one in the front is a 3/4 inch and on that same tank just behind the part of the chassis, is a 7/8 inch. Like I said, if that doesnt work, you need a new piston shaft which is rather expensive. If that is the case, avoid ANY hard acceleration as that can crack your block.

Thanks. I had already changed the oil and it was knocking before I changed it. It's not a knock from low octane fuel, there's a big difference in rattling valves from low octane gas and a hard knocking from worn bearings so I know it's not the gas. I have since quit driving the car so that I don't totally destroy the engine before I get it overhauled. Aside from the knocking at first startup and a little lower-end noise at idle the engine is super quiet and runs smooth. I think it just needs some long overdue repairs but that costs money that's not available..lol