: What other engines fit a 1999 Cadillac sts?



spares-a-hoy
04-28-08, 11:06 AM
Hello, I am new to the Caddy community. My father has a 1999 Cadillac sts that is in fantastic condition, but the n* has a blown hd gasket. After reading many threads it sounds like this is a common problem, and If I try to fix it, it will only happen again. Then what do I have. A high mileage motor with another problem. My question is, what newer year model n* engine will fit this car? I would love a low mileage n* motor, but don't know what to look for. I would appreciate any suggestions or answers from the Caddy community. Thank you.

Submariner409
04-28-08, 11:39 AM
No simple options, as the post-99 engine and drivetrain have some significant mechanical and electronic changes. If you'll take the time to go back through this forum and read the Technical Archive at the top of the page, lower left black bar, you'll see that this subject is well discussed.

Basically, after doing what amounts to a top overhaul and Timesert thread replacement on all the cylinder head bolts you will have addressed the late 90's problem: Weak head bolt retention, causing cylinder head lifting with subsequent exhaust gas in the coolant. The lower end of a Northstar is bulletproof and will last forever. You won't need to go past the chaincase and cylinder heads, but the engine unit really needs to be out of the car due to space and mechanical work constraints.

If you tackle the overhaul, it isn't a piece of cake, by any means, but the posts, pictures, techniques discussed, and workarounds posted in here will keep you straight. You have to be able to lift the car off the engine/transmission unit cradle as it and the hubs/axles all comes out the bottom.

Cost-wise, I'd do the top overhaul rather than chance a junkyard pull, unless I saw the entire car and watched to pull occur. (My 2 cents)

What's a Hoy ?? (I'm retired Navy, obviously ^^ :(chuckle))

zonie77
04-28-08, 12:07 PM
Hello, I am new to the Caddy community. My father has a 1999 Cadillac sts that is in fantastic condition, but the n* has a blown hd gasket. After reading many threads it sounds like this is a common problem, and If I try to fix it, it will only happen again. Then what do I have. A high mileage motor with another problem. My question is, what newer year model n* engine will fit this car? I would love a low mileage n* motor, but don't know what to look for. I would appreciate any suggestions or answers from the Caddy community. Thank you.

How many miles on it?

Where did you get the idea that the HG's will go again within the normal life of the car? That is NOT a normal occurance.

If the engine runs well except for the HG problem I would repair that rather than an replacing it with an unknown used engine.

I ditto submariner's post, 2000+ engines have changes that take them out of the bolt in range.

99_concours
04-28-08, 02:18 PM
I have a 99 deVille Concours in premium condition with 133K miles that I believe the head gaskets just failed. Sudden coolant usage and smell; large bubbles in the coolant resevoir observed (with cap off) that when 'pop' steam or exhaust is released. After it sat a week without being used, this weekend I started it up and now has large amounts of white 'smoke' coming from both exhaust pipes. This car has NEVER overheated, even to date. Car was well maintained. The car is still in extremely excellent shape, no scratches, dings, etc. So, this isn't a 'throw away' even though according to some of the blogs and threads I have been reading that the northstar engine may be a 'throw away'. Unbelievable that the engine that essentially 'brought back Cadillac' has such a failure record.

While I have read many of the posts, I need to simplify exactly what I should do; what is the wisest choice. I plan on removing the engine and cracking it open to determine the head bolt to block situation to determine if my engine is salvagable. No water in the oiling system so that is a good thing but what I am reading about the timeserts and powdery block alloy is disconcerting.

I see by the threads that the '99 is one of the 'bad' engines as far as timeserting...I also read that the mid 2003 the factory head bolt upgrade to LSx style bolts has a better record. So that leads me to think that the 2004 and above FWD northstars are the way to go whether used engine or a remanufactured engine knowing there were some changes with coils, etc. I saw in the above post that the post '99s are not a simple 'bolt in' replacement for a '99 and prior but I must ask what other changes would there be?

It is also my understanding that the closed deck design of the RWD northstar WILL NOT be usable in my FWD; is this correct?

So, essentially, it is my understanding that the 2004 will bolt in (with modifications) but with the LSx head bolt design this is the better choice?

It is also my understanding that the '99 northstar doesn't accept timeserts (or Norm's) very well but the 2000 thru 2003 will?

One other question: I saw something in one of the posts about someone not wanting to own a deVille up to 99 but a '98 and '99 STS is better? Was there a difference in the engine for the STS (300hp) over that of the Concours (300hp as opposed to the 275hp of the regular deVille)? Maybe it was just that, the engine horsepower. I thought the STS and the Concours had the exact same engine.

Sorry for the length of the post but there is so much information out there that I want to ensure that I am in full understanding. I might be crazy about wanting to keep my car (I actually was going to keep it indefinitely once I took it out of everyday service) but I really love the car. 300HP, and at 26mpg at 80mph is hard to beat! Add to that the quiet ride and the size of the car and its safety features (over a tin can at 33mpg) I can't find anything acceptable to replace it.

tateos
04-28-08, 02:39 PM
So, if you like the car and it is in otherwise good condition:

Drop the cradle, remove the heads and coolant crossover, insert the block you have, replace the heads and crossover, replace the cradle into the car, your engine and car will last a long time.

A used engine of that era will be prone to the same head gasket problem. Later year engines are difficult to install

Submariner409
04-28-08, 03:13 PM
The 300hp VIN 9 is the same hp engine in the three body styles. Post '99 will not bolt in with "modifications" for some of the same reasons that post '03 is not any sort of option: The electronic controls, wiring harnesses, connectors, different accessory drives and mounting make things difficult to impossible. RWD Northstars aren't even in the same ballpark. If you're worried about Timeserting the block, look at the possibility of obtaining one of the new GM short blocks for your year. There are '96 - '99 engines running in here right now which were Timeserted or Norm's inserted over the last two years. Apparently so far, so good.

zonie77
04-28-08, 05:53 PM
99C, Where did you see that 99 engines are "bad" for timeserting? I don't think they have any problems as far as inserting the block.

If you've seen that post the link so we can see what kind of problems were encountered.