: Cases resealed and new style pistons?



CadCrazy
03-17-04, 12:49 PM
Hi everyone!
I have a 98 STS that is still under the Cadillac extended warranty and I took it in the other day for an oil leak and the Mileage monitor thing for oil consumption. I was pleased to hear that they plan to put new style pistons in and reseal the cases but they want to wait till sometime in April to do it and the warranty is up in may. i wanted to have them do it as soon as possible to work out any bugs associated with the rebuild while still under warranty. Do you think they are doing this to me for that reason so I will have to pay if a problem occurs? Another question if anyone knows is the new style pistons the same high compression that is in the 98?
Also has anyone ever had this done and do you know what all they do like reconditioning the cylinder heads and new bearings etc...Do they do the timesert thing?
thanks ever so much
CadCrazy

BeelzeBob
03-17-04, 04:56 PM
Just out of curiosity, how bad is the oil consumption...????

Do you really think you will come out ahead having them take the engine completely apart and replace the pistons??? Do you know how much can go wrong in the process if the job is not done correctly...??? The car/engine is at least 6 years old, right?..and with how many miles?? The oil consumption is not a sign that anything is really wrong with the engine. Just because you are getting a set of "new" pistons does not make this a good idea.... Think about it....

CadCrazy
03-17-04, 05:57 PM
Yea I do think it is a good idea! Think about it...

BeelzeBob
03-17-04, 06:05 PM
Yea I do think it is a good idea! Think about it...


I did "think" about it....and I personally would never have that level of work done to the engine. How bad was the perceived leak and oil consumption?? It would have to be pretty bad to rip the engine completely apart for me....

CadCrazy
03-17-04, 10:45 PM
I do not need to know your personal opinion unless it is backed by experience with the northstar in my car. New pistons is a good idea!!! I just want to know if they are the same compression. These new pistons are designed differently by engineers(are you one)that made them especially for the oil consumption in mind. My car used 4 quarts of oil in 1300 miles, with 47000 miles on the car. I rarely post on this board because of responses like yours. If they are going to rebuild the entire engine then absolutely it is a good idea. I just do not know exactly what they are going to do and your opinion is not based any at all on facts or knowledge about what is going on....

509Rider
03-17-04, 10:52 PM
You might want to listen to bbobynski, I have read lots of his comments and he knows more than most people on here.

BeelzeBob
03-17-04, 11:12 PM
I do not need to know your personal opinion unless it is backed by experience with the northstar in my car. New pistons is a good idea!!! I just want to know if they are the same compression. These new pistons are designed differently by engineers(are you one)that made them especially for the oil consumption in mind. My car used 4 quarts of oil in 1300 miles, with 47000 miles on the car. I rarely post on this board because of responses like yours. If they are going to rebuild the entire engine then absolutely it is a good idea. I just do not know exactly what they are going to do and your opinion is not based any at all on facts or knowledge about what is going on....

If you don't want the opinions then just skip over the post.....that is the problem with internet forums...you get responses from everyone.....LOL Since you willing admit that you do not know much about the engine or what they are going to do you might want to read and understand the infor provided, though, as the "opinions" are from a reasonable knowlegable source....

Yes, actually I am an engineer that works on the Northstar engine.

There are many factors involving oil consumption. If you haven't followed any of the info I have posted you can still search using the search feature on the forum using "oil consumption" and read up. Then you will be much more knowlegeable about what may be going on.

My comments to you are taking a lot of things into consideration that you may not even be aware of. There are many many things that can go wrong with a complete engine teardown and piston replacement. I can't imagine the engine and vehicle having the same integrity after the job that it had before. It is a very involved procedure involving disassembling the engine to it's most elemental parts. Hope you get a good tech......

Your original post just mentions the fact that you are getting new pistons...nothing about the oil consumption that you are experiencing or anything else. If the oil consumption is really 4 quarts per 1300 miles (I would expect a trail of blue smoke with that kind of consumption, actually, so it is a bit hard to believe) then something is obviously wrong and it is hard to believe the car/engine made it to 47,000 with no previous complaints. If the engine is not smoking then there is likely nothing wrong with it. Read the "oil consumption" postings for an explaination. If there is nothing wrong then why tear the engine apart. Set the correct level, do the WOT cycles to exercise the rings and make sure that they are mobile and seated and I would be surprised if the oil consumption stays that high......

Internet forums are just that, forums where people express their opinions. When you ask for them by posting then you really can't criticize them just because they don't agree with you. You are correct that my opinion was not based on all the facts...it was just based on the facts that you provided in your original post. So I should be a mind reader...??? My input IS based on extensive knowlege of the Northstar engine and experience with it from the design of the engine thru it's development and validation testings and the manufacturing of the engine.

BTW...the compression ratio of the replacement service pistons is the same as the original pistons. The ring pack was redesigned for service applications in cases of severe oil consumption complaints so as to be as "dry" as possible with higher ring tensions, more aggressive oil rails, etc.... The penalty is higher friction which negatively affects the power and fuel economy slightly.

ThomasO
03-17-04, 11:32 PM
I do not need to know your personal opinion unless it is backed by experience with the northstar in my car. New pistons is a good idea!!! I just want to know if they are the same compression. These new pistons are designed differently by engineers(are you one)that made them especially for the oil consumption in mind. My car used 4 quarts of oil in 1300 miles, with 47000 miles on the car. I rarely post on this board because of responses like yours. If they are going to rebuild the entire engine then absolutely it is a good idea. I just do not know exactly what they are going to do and your opinion is not based any at all on facts or knowledge about what is going on.... Hey CadCrazy (interesting handle), tell you what, I'd keep quiet and listen thankfully to the folks in this forum before I'd put all my faith in what a dealership says, considering they are going to get payed by GM/Cadillac for doing this complete overhaul of your car. Hey, maybe you need it, but a little welcome discussion here from these good people may open your eyes to something you need to know. If we did have all the information you could provide some here might agree with you and your dealership, but getting different views and ideas is what this forum is all about and you should be grateful instead of hostile. Stick around, you might learn something if you don't already know it all.........Tom

JimD
03-18-04, 12:39 AM
I do not need to know your personal opinion unless it is backed by experience with the northstar in my car. New pistons is a good idea!!! I just want to know if they are the same compression. These new pistons are designed differently by engineers(are you one)that made them especially for the oil consumption in mind. My car used 4 quarts of oil in 1300 miles, with 47000 miles on the car. I rarely post on this board because of responses like yours. If they are going to rebuild the entire engine then absolutely it is a good idea. I just do not know exactly what they are going to do and your opinion is not based any at all on facts or knowledge about what is going on....

You "rarely post on this board because of responses like yours" ?? There are countless thousands of places on the internet where that comment would be accurate/appropriate. You have stumbled onto one of the precious few internet sites where accurate engineering/technical information is available for the asking!

The free advice Bbobynski is offering you is worth reading three or four times. The man knows whereof he speaks.

Period.

CadCrazy
03-18-04, 12:41 PM
If you don't want the opinions then just skip over the post.....that is the problem with internet forums...you get responses from everyone.....LOL Since you willing admit that you do not know much about the engine or what they are going to do you might want to read and understand the infor provided, though, as the "opinions" are from a reasonable knowlegable source....

Yes, actually I am an engineer that works on the Northstar engine.

There are many factors involving oil consumption. If you haven't followed any of the info I have posted you can still search using the search feature on the forum using "oil consumption" and read up. Then you will be much more knowlegeable about what may be going on.

My comments to you are taking a lot of things into consideration that you may not even be aware of. There are many many things that can go wrong with a complete engine teardown and piston replacement. I can't imagine the engine and vehicle having the same integrity after the job that it had before. It is a very involved procedure involving disassembling the engine to it's most elemental parts. Hope you get a good tech......

Your original post just mentions the fact that you are getting new pistons...nothing about the oil consumption that you are experiencing or anything else. If the oil consumption is really 4 quarts per 1300 miles (I would expect a trail of blue smoke with that kind of consumption, actually, so it is a bit hard to believe) then something is obviously wrong and it is hard to believe the car/engine made it to 47,000 with no previous complaints. If the engine is not smoking then there is likely nothing wrong with it. Read the "oil consumption" postings for an explaination. If there is nothing wrong then why tear the engine apart. Set the correct level, do the WOT cycles to exercise the rings and make sure that they are mobile and seated and I would be surprised if the oil consumption stays that high......

Internet forums are just that, forums where people express their opinions. When you ask for them by posting then you really can't criticize them just because they don't agree with you. You are correct that my opinion was not based on all the facts...it was just based on the facts that you provided in your original post. So I should be a mind reader...??? My input IS based on extensive knowlege of the Northstar engine and experience with it from the design of the engine thru it's development and validation testings and the manufacturing of the engine.

BTW...the compression ratio of the replacement service pistons is the same as the original pistons. The ring pack was redesigned for service applications in cases of severe oil consumption complaints so as to be as "dry" as possible with higher ring tensions, more aggressive oil rails, etc.... The penalty is higher friction which negatively affects the power and fuel economy slightly.


Okay, I believe you now :canttalk:
When I took it in for the oil consumption test they said it was 4 quarts low . True or not I do not know. I know it read check oil level on the display. BTW
this northstar loves the WOT and gets it quite frequently. No blue smoke though.
I do not intentionaly critize people. The Think about it line is what got me with nothing directly factual or informative in its prelude. You also say I did not mention the oil consumption thing in my first post but I did. You have a tendency to retaliate as " So I should be a mind reader...??? " implies.
I know how dealers and techs are from experience. I always have to go through what they done by way of tiddying things up. The whole thing doesnt really bother me except for the warranty is about to expire and I see problems that may occur from what they plan to do. My wife thinks it will take two additional visits to work it all out in the end but I say four. I just want more time but dont have it and am concerned at my wallet for it. I will say at first I was excited about haveing a "new motor" just as the warranty dies but now I am feeling mixed on the matter. I just want to know if anyone else has had this done and what their experience has been. I totaly agree with the comment; "I can't imagine the engine and vehicle having the same integrity after the job that it had before."
CadCrazy

CadCrazy
03-18-04, 12:49 PM
Hey CadCrazy (interesting handle), tell you what, I'd keep quiet and listen thankfully to the folks in this forum before I'd put all my faith in what a dealership says, considering they are going to get payed by GM/Cadillac for doing this complete overhaul of your car. Hey, maybe you need it, but a little welcome discussion here from these good people may open your eyes to something you need to know. If we did have all the information you could provide some here might agree with you and your dealership, but getting different views and ideas is what this forum is all about and you should be grateful instead of hostile. Stick around, you might learn something if you don't already know it all.........Tom


Thank you Tom. I do not know it all and have never been that way. I do tend to get overly hostile at times. I am always able to justify it though. Atleast in my mind..LOL :bonkers:
Rick

ThomasO
03-18-04, 01:10 PM
CC, you may hopefully get more direct input here on your particular problem, but in the mean time you may want to peruse these:

http://www.cadillacforums.com/forums/search.php?searchid=54580

RAD
03-18-04, 01:27 PM
Hey there 'CC'..I don't post on this forum much, but for what it's worth, I have been actively involved on another for some years now. One of the things I have learned after having 3 STS's, 92, 93 and a 2000, is if the darn thing likes a quart of oil now and then, even every 1000 miles..So what? It just doesn't concern me that a high performance motor gets a little thirsty. It certainaly isn't a quality problem, it's just the 'nature of the beast'. On my '93 STS with 85k miles, I just wait untill the oil check message ocurrs, and add two quarts. On average this happens once between oil changes as dictated by the OBD. I figure it's like a fresh mini oil change inbetween. I drive the heck out of that motor, and it's never complained.
In retrospect, if the dealer offered me new pistons for a perfectly great running motor that used a little oil, I'd turn him down without a second thought.
I've read about too many horror storys over the years, relating to owners that had realtivly minor intrusive work done on a formerly great running motor. Unless it's a major failure, nobody's touching mine..;)

BeelzeBob
03-19-04, 12:03 PM
"When I took it in for the oil consumption test they said it was 4 quarts low . True or not I do not know. I know it read check oil level on the display. "


Instead of questioning the advice/comments you get maybe you should take a crash course in checking your oil level.....LOL.....just kidding.

The "check oil level" message comes on when the system is 2 - 2.5 quarts low....not 4. If it was really 4 quarts low the message must have been evident for several days.... Did you open the hood and check the oil?? Usually that is all that is required....checking and adding a quart occasionally. Not new pistons.

Sorry to be hostile back at you but I post often enough that if you bothered to read at least a few of the topics you should start to get the idea that my posts are usually factual and to the point. I don't post my references everytime I post something. Your original post just reeked of the "I'm getting new pistons for free so it must be a good thing.....just because I'm getting something for free.." type of logic and I wanted to make sure that the idea that tearing the motor apart for basically nothing was not such a good idea. "Pistons" will last hundreds of thousands of miles in a Northstar engine so they don't need replacing very often...and getting "free" ones is not necessarily a good thing.

Understand that the Northstar is a high performance engine and will use some oil due to the total loss nature of lubricating the top rings and the (32) valve guides. Some oil consumption is a good thing, actually, and to the engineers that designed and developed the engine oil consumption is really not too much of an issue. It is accepted as the nature of the beast for a high performance, high revving engine. Too bad that customers cannot accept the same logic. Moderate oil consumption without any blue smoke is really nothing to be worried about. Unless an engine uses tremendous amounts of oil or is smoking or suddenly the oil consumption/smoke changes dramatically there is likely nothing wrong nor will anything go wrong. Put oil in it occasionally and drive the snot out of it. That is what it was designed for.

Jack Ammann
03-19-04, 12:23 PM
I do not need to know your personal opinion unless it is backed by experience with the northstar in my car. New pistons is a good idea!!! I just want to know if they are the same compression. These new pistons are designed differently by engineers(are you one)that made them especially for the oil consumption in mind. My car used 4 quarts of oil in 1300 miles, with 47000 miles on the car. I rarely post on this board because of responses like yours. If they are going to rebuild the entire engine then absolutely it is a good idea. I just do not know exactly what they are going to do and your opinion is not based any at all on facts or knowledge about what is going on....

Mr "CadCrazy": You're talking to a GM/Cadillac Powertrain Engineer, specializing in the Northstar engine. You would do VERY well to familiarize yourself with these people before making comments like those above. Those kind of comments do nothing for your veracity...something about "just keep your mouth shut a look ignorant rather than open it and...."well, you know the rest.

CadCrazy
03-19-04, 01:07 PM
"When I took it in for the oil consumption test they said it was 4 quarts low . True or not I do not know. I know it read check oil level on the display. "


Instead of questioning the advice/comments you get maybe you should take a crash course in checking your oil level.....LOL.....just kidding.

The "check oil level" message comes on when the system is 2 - 2.5 quarts low....not 4. If it was really 4 quarts low the message must have been evident for several days.... Did you open the hood and check the oil?? Usually that is all that is required....checking and adding a quart occasionally. Not new pistons.

Sorry to be hostile back at you but I post often enough that if you bothered to read at least a few of the topics you should start to get the idea that my posts are usually factual and to the point. I don't post my references everytime I post something. Your original post just reeked of the "I'm getting new pistons for free so it must be a good thing.....just because I'm getting something for free.." type of logic and I wanted to make sure that the idea that tearing the motor apart for basically nothing was not such a good idea. "Pistons" will last hundreds of thousands of miles in a Northstar engine so they don't need replacing very often...and getting "free" ones is not necessarily a good thing.

Understand that the Northstar is a high performance engine and will use some oil due to the total loss nature of lubricating the top rings and the (32) valve guides. Some oil consumption is a good thing, actually, and to the engineers that designed and developed the engine oil consumption is really not too much of an issue. It is accepted as the nature of the beast for a high performance, high revving engine. Too bad that customers cannot accept the same logic. Moderate oil consumption without any blue smoke is really nothing to be worried about. Unless an engine uses tremendous amounts of oil or is smoking or suddenly the oil consumption/smoke changes dramatically there is likely nothing wrong nor will anything go wrong. Put oil in it occasionally and drive the snot out of it. That is what it was designed for.


Hey no digs this time...Thanks lol. the just kidding thing uplifted me and made me smile....It's the little things bbobynski. Yes the check oil level thing was on for several days because the dealer said to call when it came on and then when I did they made an appointment for the next week so I did not add any oil.

"I'm getting new pistons for free so it must be a good thing" YES that is what I thought he he . Really I was thinking of getting the heads for 2500 that are supposed to give more horsepower and the dealer said they would put them on during the ass. procedure. But I do not know if they really give any performance . I did read alot of your posts and YES you put me in my place....
Someone here bought the heads but I cant find any info on his success or not..I believe it was shadowlvr. I will look further
Thanks
Rick

CadCrazy
03-19-04, 01:11 PM
Mr "CadCrazy": You're talking to a GM/Cadillac Powertrain Engineer, specializing in the Northstar engine. You would do VERY well to familiarize yourself with these people before making comments like those above. Those kind of comments do nothing for your veracity...something about "just keep your mouth shut a look ignorant rather than open it and...."well, you know the rest.

Were past that now Jack. Thanks for the kind words..... :tease:

BeelzeBob
03-19-04, 01:16 PM
I would not recommend the ported cylinder heads, personally. A lot of money for a questionable gain. Personally, I have not seen any perceptible performance gains with head porting on the Northstar IN A PRODUCTION CAR. There is a big difference between a Northstar in a sand rail that is running with a manual trans in a light car that is shifted at 8000 RPM and pullling a 4000+ pound luxury car around with an automatic trans. The head porting looks good on a flow bench..and may even bump up the peak HP number...but it can cost torque at lower RPM's and actually hurt performance. Some head portings that I have seen have increased flow on the flow bunch but would not even run well on the dyno as the tumble and swirl characteristics of the heads were altered so severely that the engine would not run correctly at the air/fuel ratios programmed into the factory PCM that are required for engine detonation and preignition protection. The cars in those cases actually slowed down.


If you want speed, spend the money on a higher stall torque converter to launch the car better and allow the engine to reach the higher operating RPM quicker. MUCH more bang for the buck.

CadCrazy
03-19-04, 01:40 PM
Yes I think I will do that....Thanks..Soo far I have installed a hi flow cat and the corsa exhaust with the K& N filter. I tried the Grannatelli mass air flow thing and it did nothing at the track...ZERO gain!!! Waste of money. I also cut the y pipe apart at the exhaust manifolds and removed the inserts that reduce the exhaust flow then tig welded it back together. It was just a test and it worked... Even made it a little louder to. Has plenty of take off power but at the top it seems to drop off...Not enough horsepower???
I will look back at one of your posts to see where to locate that torque convertor. thanks
Rick

BeelzeBob
03-19-04, 02:05 PM
Yes I think I will do that....Thanks..Soo far I have installed a hi flow cat and the corsa exhaust with the K& N filter. I tried the Grannatelli mass air flow thing and it did nothing at the track...ZERO gain!!! Waste of money. I also cut the y pipe apart at the exhaust manifolds and removed the inserts that reduce the exhaust flow then tig welded it back together. It was just a test and it worked... Even made it a little louder to. Has plenty of take off power but at the top it seems to drop off...Not enough horsepower???
I will look back at one of your posts to see where to locate that torque convertor. thanks
Rick
Get ahold of Yank Converters at 501-632-6355

the little STS
03-21-04, 11:52 PM
bbobynski ur my hero