View Full Version : 6 oil leaks; gaskets replaced now intake plenum boot replaced..

10-09-09, 04:31 PM
I'd sure appreciate some subject matter expert feedback...

the problems:

Have 2002 Deville, 73.0k miles, Maintained by dealer since new. has been trouble free mechanically - vogue tires of course have been problematic.

.....Recently dealer found oil leak, turned out there were 6 leaks that requried dismantling the engine and replacing gaskets on the "...three sections of the engine..."

.....This past week "check engine soon" light... Dealer had to replace the "split intake plenum boot".

the reason advised by dealer:

Northstar designed as a race car engine; since I don't drive it hard, these oil leaks/gasket problems are a result.

All seems to be fine now but.... I'm having trouble with the long-term integrity of the engine and certainly owning this car without an extended warranty.


1) Am I getting smoke blown in my ear regarding the oil leaks/replacement of gaskets & plenum boot problems; or is there credibility to the dealers opinion that the engine is not being driven as designed (as a race car)?

2) Have other experienced this situation or do I have unique problems?


10-09-09, 04:49 PM
There is some truth to that, but I don't think it pertains to gaskets. Go to the Technical Archives at the top left of this page and read up on "oil consumption" and "full throttle is good for your engine".

10-09-09, 04:55 PM
The oil leaks (probably cam cover(s), half case and oil pan) are caused by slow failure of the O-ring style of silicone "gaskets" used. The Northstar is essentially a one-piece engine when fully assembled because there is NO tolerance for parts movement or gasket compression, particularly at the half-case joint. The half-case is essentially all 5 crankshaft bearing lower halves and a stud girdle in one piece. You cannot use a gasket there because of bearing requirements.

The leaks are not a result of not having run the car hard, and the intake manifold plenum leak is an all-too-common post-2000 Northstar problem.

Your engine should be just fine for a long, long time now.

Read the entire Cadillac Technical Archive up in the black bar ^^^, especially the section "Occasional full throttle operation is good for your engine". Subscribe your car for one or more years to www.alldatadiy.com. Read the entire sticky thread at the top of the main Deville page titled "How to pull codes" and use the URL with "obd2" in the main address line. (Diagnostic trouble Codes, from your car's built-in code scanner/reader.) Then return to the link with any codes and whether they are Current or History and click on the links for P,B,C, and U codes to get definitions.

Read as much of Deville and Northstar Performance as you can stand.

Welcome Aboard !!!!!!!!!!:highfive:

10-09-09, 05:12 PM
I agree with the above, and I don't want to be Destroyer Jr., but after 8-9 years and 73K+ miles, I think you should be at least prepared to hear about one more common gasket failure area - head gaskets.

10-09-09, 05:44 PM
If you get past the oil leaks and possibly a set of crankshaft position sensors (extremely common on '00-'03 Northstar's) with no other motor trouble you'll be golden. Since you've already fixed a common problem with your car and the plenum is done, you should be good. Just make sure your coolant is changed on time (5yrs/150,000 miles) and you give the car a good wide open throttle (WOT) to keep everything cleaned out.

You should be fine. Just enjoy your car! :D