What are the most common things that fail on the devilles?

things electronically and alike I would like to replace some of them and watch out for the other so I can know what to expect.

Does anyone know if any of the deville parts are interchangeable with other years or other Gm cars? If yes please list them

Thanks

What are the most common things that fail on the devilles?

The drivers, mostly. They fail to maintain the car as recommended by the factory.

All kidding aside, that's a very difficult question to answer. Devilles have been produced in one form or another for what, about 50 years? Are you talking a '63 Coupe DeVille with 330,000 miles on it, or a 2005 Deville DTS off the showroom floor?

Devilles since about 94 have had the Northstar engine. Some people curse it. Some love it. There is no good answer. Coolant maintenance is VERY important with these engines. However, it's also very easy. Every two years, take it to a shop you trust, or do it your self : Unhook the lower radiator hose. Let as much coolant as will come out, come out. I recommend Against letting it drain into your neighbors lawn. When no more stuff drips out, pop either TWO tubes or SIX tablets of the Bars Leak Golden seal stuff (available at your local WalMart) in the lower rad hose, button 'er back up, and fill with a 50/50 mix of drinkable water and Dexcool or a derivative. IF, and very important IF, the engine has has NON DEXCOOL put into it at any time, repeat the above procedure every two years. If only Dexcool, repeat every five years.

A simple search of the archival storage on this voluminous site will regale you with hours of entertainment and knowledge. Don't let the crybabies get you down, and listen to the "evangelistas" with a tiny grain of salt too. Remember, the truth probably lies somewhere in between....

aim interested in the 96 deville im going to be replacing the head gaskets on it and i wanted to know what else i should do at the same time ?

At the risk of telling you what you already know, Timesert ALL the head bolt holes.