How to determine engine's health?
 

I posted this on another site, but this one gets a lot more traffic and I was hoping to have quick responses. Here is my dilema:

Perhaps due to all of the issues I have had with my car, I have lost a bit of faith in it and actually put it up for sale. Even though I have had some low ball offers, I am not taking them. All of this has made me re think about actually selling the car or not. Are there any definite tests that can be done to determine if my engine will let go sooner than later? If I can do this and see that I do in fact have a healthy engine, then I may decide to just keep the car, after all, I have replaced so many things on it that the only major thing that worries me to repair is the engine itself! The reason for my uncertainty about the engine is due to the "questionable reliability" stigma associated with early 996s (mine is a 98 RoW) and the fact that my car, while idles steady, makes the passenger seat shake a bit. So, is this leakdown and compression? Anything else specific to 996s that mechanics could use to determine the health of the engine (without having to take it apart that is...).
Thanks in advance for the replies!

Do a complete engine compression test. Also, fuel injection cleaning.

while a compression check will tell you how well the engine is doing in terms of wear and tear, i think the reliability questions are in concern to the intermediary shaft going (complete engine replacement) and the rms (more of an annoyance)

i don't know how to check/insure longevity in the intermediary shaft, but would like to hear more if anyone knows anything

When I first got the car, I thought I had the RMS, but after using the car, it disappeared! My car sat for nearly a year before I bought it. Just goes to prove that these things are meant to be driven.
Intermediary shaft.... humm... Any idea how to check for that one?

You cant do much for the IMS, however, there is an upgraded cover bolt that replaces the old one, which is not as strong and the IMS can shear them....

is that what has caused the ims falues? shearing of the bolt covers?

i do not understand the failures clearly just trying to understand more fully.....

why do they recomend replacing the engine for just some bolts that shear off?

and what the heck is an intermediary shaft anyways? :)

I am not sure where I read this but you can have your oil analized. A company called Blackstone Laboratories does this and states "Oil analysis is a quick, nondestructive way to gauge the health of an engine by looking at what's in the oil." This sounds like a good and inexpensive way to help you get a better feel for your engines longevity. Here's a link. Doug
http://www.blackstone-labs.com/what_..._analysis.html

I wonder if used engine oil is considered hazardous and flamable material.... I live overseas, otherwise, I would not hesitate in sending the oil out for analysis.

oil analysis and compression and leakdown combined should give you a farly good picture of averall health but is no guarantee that you won't have some random mechanical failure. I replaced my engine after losing all compression on number 2. Internal inspection of the cylinder using a scope showed no debris or holes in the cylinder leading me to believe that one of the exhaust valve springs had failed. Not something that will show up in testing.