Northstar V8

[paulg]

Ok, sorry for the off-topic. However, since the topic of Cadillacs came up I wish to tap the brains of the geniuses that read these posts.
My buggy is a 2003 DeVille with Northstar V8. Serviced entirely by the dealer to this day.
Well, it has 125000 miles and is starting to consume oil. If you let it idle for a long while the exhaust will start to turn blue. Car still runs and looks fabulous.
Here's the question: What do you recommend for this aged engine? Can I use a thicker oil? I've tried some Castrol old-engine oil which seems to lessen the whispy smoke somewhat. What are the tricks to squeezing out a few more years without fouling the zillion sensors or locking up the block?
FORGET about getting the engine rebuilt. Neither the dealer or servicers will fix it. They'll all drop a block in it for $4800. Forget it!
So as this car fades away and trade-in times loom in the future, what can I do to extend its useful life? All comments welcome. I'm not gonna let this topic loom too long on this site but since we have some Caddy-luvers out there I'd like to hear what they say!

 

[austinado16]

I'll say that 125k is nothing on modern fuel injected engines. To give you an example, our '90 Suburban has 269k and our '95 Audi A6 Avant has 230k. Both on their original engines.

I'm not a GM tech, so I'll speak in general terms since I don't know the northstar engine.

You should run the synthetic oil weight that your owner's manual recommends for your current cold start climate conditions. That may simply be 5w/30. But look it up to make sure. I would put any "High Mileage" wiz-bang oil into any engine, especially not yours.

Use only the GM Delco oil filters or at a minimum, NAPA Gold or Wix filters.

Never get your oil changed by schlock places like Jiffy Lube.

It's not very common that a modern engine will smoke blue at all, because the catalytic converters will burn the oil out of the exhaust. So when blue smoke is visible, that's quite a bit of oil being consumed.

Generally, blue smoke at idle, and on cold start, is oil leaking down the valve stems past the valve stem seals and right into the intake ports where it is sucked into the engine and burned. Same thing happens down the exhaust guides, but the oil goes right into the exhaust system and out the tailpipe.

In most engines valve stem seals can be replaced with the engine in the car, and the cylinder heads on. But, I'm not familiar with the layout of the northstar's heads, so I don't know if that's true.

Another cause for smoke in the exhaust is a clogged crankcase breather system. Depends on how the crankcase fumes/pressure is routed. So you can have that checked.

I'm doubting you have a piston ring problem because there just aren't enough miles on the engine.

I've heard the northstar engines can blow headgaskets and due to the headbolt design they are not repairable. Something about the head bolts snapping off if they are attempted to be removed....so the solution has been to drop in a crate engine, like you were quoted.

So...I would change the oil and filter and put in the correct weight of synthetic. Have the crankcase breather system checked. Buy a can of Seafoam fuel injection cleaner from NAPA autoparts and put that in with a full tank of fuel. And then see what happens, keeping an eye on oil consumption.

Finally, I'd ask the dealership if they are able to replace the valve stem seals and if so, how much $.

Don't trade it in. Put in on CL where you'll get a lot more money for it then you will the make-believe-trade-in-money that a stealship offers you. Used cars is how they make their money, and they get back every dime from you, on the back end of the loan.....and then sell the car for double what you were given.

 

[washernoob]

Wow! 269k on a suburban! Thats impressive. Ive got a buddy with a Ford turbodiesel truck with 300k on it.

Its amazing. Some vehicles dont last past 140k and some last more than 300k.

My baby has 135k on it. He's burning more than normal on oil too. But hey its older, and thats just the way things work sometimes I guess. Hes not worth putting new head gaskets in, so I will just stick with it using more oil. It doesn't have a burning smell though, which is ok.

Dont worry though. It cant be as bad as my friends 2002 Dodge Stratus! He puts a quart in it a week; it burns so bad!

 

[xraytech]

I hd a 2001 DeVille, I had 74,000 miles on it when I traded it, at 68,000 miles it really started coming apart at the seams, new transmission(common problemwith that model) ignition coil, intake manifi=old, then it really started leaking antifreeze so it had to go before it blew the head gasket. Mine al;ways burned about 1 quart of oil every 1,100 miles, and to my understanding the burning oil is supposed to be normal on those engines.
When I tried to trade it in I wanted to go to Lincoln and I had a few Lincoln-Mercury dealers refuse to take it on trade because they lost so much money on them blowing their gaskets whil estill under the 3 month/3,000 mil eused car warranty. I had to sell on craigslist and got a little more than used car dealers would give as a trade in.

 

[roto204]

Northstars

Northstars generally are good for about 100,000 miles, and that's about it. (Look in auto listings for Caddies with Northstars around the 100K mark, and you'll see many with replaced engines.) They're extremely technologically advanced, including their capability of running by modulating cylinders two-by-two to operate without coolant, but for whatever reason--design, aggressive cylinder honing, or whatever--they seem to top-out around the 100,000 mile mark.

The oil burning can happen due to non-synthetic oils allowing the rings to stick in their grooves, or due to earlier iterations of the engine that had pistons with rings higher-up on the collar. This can result in high hydrocarbon counts when emissions testing, too.

Weightier synthetic oil may help, but it may be temporary relief at best.

What's your oil consumption? In the mid-2000s, 1 quart per 1000 miles was considered average for Northstars.

 

[qsd-dan]

Cadillac considers (and they have this in writing) that burning 1 quart of oil every 500 miles is considered "normal" for all northstar engines, whether the engine is new, broken in, or worn out. I find those specs ridiculous, but that's how they engineered it.

Another cause for smoke in the exhaust is a clogged crankcase breather system. Depends on how the crankcase fumes/pressure is routed. So you can have that checked.

BINGO!

Check all of the hoses for clogs, bends, and twists. Some of those hoses collapse when they get old since they're under a a constant vacuum. Check the PCV valve and any breather elements for excess build-up or clogging. Usually when any of the above occurs, you'll have a moisture (looks milky) substance built up on the backside of the oil cap.

For the most part, using thicker oil is never a problem. Most manuals state 5-20/5-30 weight oils 'cause they're obeying what the natzi "greenies" push on them. Thin oil is purely political unless the manufacturer has extremely tight tolerances in the lower end.

To make my point, 5/20 is recommended by Honda for my '99 Accord in the USA. 10/30 is recommended for the same EXACT engine overseas. 10/30 oil runs smoother and quieter, with no change in gas mileage, so that's what I use. Never had a problem in 12 years and 121,00 miles and it still doesn't burn any oil between 4K mile oil changes.

 

[roto204]

Right on, Dan and Todd

PCV breather clogging was on the list too

 

[cadman]

Paul,

Interesting topic. These engines ARE designed to use oil- 1qt per 1000 to 1500 miles is normal (anyone interested in the technical reasons, see the link). However, you should not be seeing blue smoke from the exhaust. How frequently are you needing to top off?

The Northstar was originally conceived as a high performance, advanced tech mill. I still remember when it debuted- 300HP in the Eldo, wild stuff. Unfortunately, grandma never cracking 3000 RPMs for 50,000 miles on such a design can cause problems down the road, and many didn't use the premium fuel required, either. Cadillac went through a similar issue on its hot 429 in the 60's with rings not seating, some sticking and others breaking loose years later due to light driving.

If I were in your shoes, I'd have a compression check done. Oil is either getting past your rings, or around your valve seals (which should last a lot longer than a 100k). -Cory

http://bleudog.cc.emory.edu/archives/cml/Sep_03/0045.html

 

[paulg]

Great stuff

Thanks much for all the astute suggestions. I am greatly appreciating the help.
The engine shows a little blue whispy smoke from the exhaust when warm rather than cold. You won't see it when driving, but sometimes after longer idle.
Your suggestions of what to check for this symptom lead me to believe I made a few mistakes.
First, I took the unit back to the dealer immediately upon first notice of the issue. That in itself is not a mistake but I'll explain later. The dealer kept it overnight and essentially quoted a high price to partially disassemble the engine to find what is wrong. Did I want to spend $1000 for an invasive estimate? Not really.
Nor do I blame them. I do understand that they have to dig. They made no mention though of breathers or PCVs potentially causing the issue.
Actually I don't blame them for that either. If the likelihood of breather or PCV issues being true cause is too low, they may just estimate for the block and be done with it.
My mistake was not getting a second estimate. I got SECOND quotes on engine replacement but NOT an estimate for true cause of trouble of the original engine.
Presently, the car is due for an oil change. This time I will take it to the other Cadillac dealer and get the car checked again. What I may do is pay for PCV and breather replacement AS A TEST, and check hoses and other items mentioned by you all. I AM willing to spend a few bucks to try things even if they don't ultimately cure the symptom.
I am not a mechanic, but my logic makes me think that due to the age of the car, it is possible that multiple factors may be causing oil consumption. If the replacement of PCV, breather and hoses REDUCES oil consumption (but does not eliminate it entirely), it may be money well spent!
Heck, I'm not expecting new-engine performance since the engine is not new.
I top off the oil with 5W30 at about a quart every 500-700 miles. The car has been expressway driven its entire life which is a good thing.
Overall it is serving me well and is worth a few bucks for another estimate, and a little preventative maintenance. I'll cross my fingers and see if it gets me through another Winter.
Great tip on the trade-in value. Using Craig's list or equivalent to get the car to the right somebody at the right price is... RIGHT ON! The dealers will have me pegged as I drive up and I don't want that grief.
Again thanks for the tips. I truly dislike buying cars more than anything and possibly elongating the life of the car will help matters overall. Much obliged!