You might want to go to Engines, Northstar Performance and read through the sticky post at the top of the threads forum - the informal survey on head gasket failures by model year. 1998 and 1999 are (non-scientifically) the worst years for problems in that department.... and for the non-mechanic that's a $3,000 - $5,500 repair.
Yeah and that is why I thought that info was interesting. 44 reviews and a 8.9 rating on the 1999! Here is the link:
http://autos.msn.com/research/vip/Reliability.aspx?year=1999&make=Cadillac&model=Eldorado
I have a friend that works at Cadillac. He also said 96-02 were the most problematic. Of course, the problem is if you want an Eldorado, you are pretty much out of luck, unless you go for a pre-96 based on what he said. The 1999 I am looking at is a pearl white base model (not esc or etc) with 75k miles. According
to the seller/dealer, he just drove it to Miami and back this week with no issues. No leaks, everything 100%.
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A 99 Sts is more reliable than a 02 Sts? Well, statistically it will have 3 more years of avg miles so add 40k miles. But you are buying both cars today. I would put my money on a 02-03 Sts being in better shape.
Luckily, this is snowbird country! There are alot of low mileage Caddies around here! In fact, I talked to someone yesterday who had a garage kept 96 Concourse wih 51k! Problem is, it's got oil and coolant leaks..... Like I said, the 99 Eldorado, 75k miles and the 99 STS (nice, its black on black) has 90k.
I did find a 2002 SLS, but it has 125k on it. It's priced at $5,000. Seems a little steep.