Northstars commonly have bad "midseal"?

[BodybyFisher]

I am not sure what we are trying to say here. We have more than once said that these engines tend to leak oil. Over and over we have heard this. Mine is always wet on the bottom and that has been my experience with other Northstars. Now maybe that is because I am looking at mainly old Northstars and they stopped the leaking problem, is that the case? (case, no pun intended, lol)

Mine?, leaks like a sieve, and my wife is po'd that I park it in the driveway, my friend has a 94 complete with an OIL STAIN in his driveway. If I use 10W30, I smell oil burning it leaks so badly

Now early on I saw this statement >> "and most every car has an oily bottom from overspills on oil changes, overspill of any other fluid and from oil filters that naturally leak a little bit", << I am not sure how true that statement is, overspills?, I use a funnel, no overspills, overspills of other fluid?, no I use funnels, and oil filters that 'naturally' leak a little, nope, mine has NO leak nor have I every known an oil filter to leak. Many people think that if they tighten their oil filters too much that they will never get them off, THEN they leak. I am big on oil filter sockets that fit the bottom of the filter, given how little room there is to get a wrench in there. Are you using an oil filter socket?

Here is the bottom line, these things leak oil like a sieve, now maybe some out there don't or the problem has been corrected, or maybe its because I am driving a dinosaur, but it is NO secret that they CAN and DO leak badly, you see a wet bottom and the NATURAL conclusion is OIL LEAK.

I need to rebuild mine, and I will be thrilled, if I can stop it from leaking. But lets not delude ourselves that these engines dont leak oil, SOME leak badly and I would venture to conclude that the popular thinking out there IS that Northstars leak oil.

The fact is, the bottom of CoupeDTS's bottom is WET, that fact equates to a problem of some sort. It is highly unlikely that 'overspill' accounts for a wet bottom NOR would the dealer believe the SELLER that it is due to overspill as all parties are SUPPOSE to act in self-interest! It is THEIR job to inspect the car and identify potential problems that will contribute to a HARD SELL, so they tally up, and deduct the potential cost to repair the job, OR, the additional time it takes to sell the car due to the obvious scary problem that all one needs to do it KNEEL down to see it...

But when the sell it, they will minimize it, saying ALL NORTHSTARS leak....

I do not think a dealer is out of line for changing a trade-in price once a mechanic inspects it. Keep in mind that IF the mechanic fluffs off a problem, when it cant sell because of the problem, the mechanic's AZZ is on the line. When they take it to an auction, THOSE SHARKS will SPOT everything and it WONT sell or it will sell for a REDUCED price and THEY know that....

[CarlaValentine]

Well I for one am relieved to know that a small oil leak on a nothstar is "normal" (I put it that way because i still see some debate on this issue). I was wondering though, how does everyone define little? I changed my oil last at the end of October. Since then have put a little under 3,000 miles on it, the oil life indicator is at 43%, and I have had to add a little over 2 quarts to it since then. There is a small puddle in my driveway, about the size of a baseball maybe. The only 2 places I have seen a leak are the oil pan gasket (seems to seep all the way around, but only drips in the back) and the rear valve cover.

[BodybyFisher]

43% is the oil life its nothing to do with leaking or consuming oil, its the oil estimated life based on the way your use your vehicles, short trips are harder on the oil than long trips and the oil life monitor uses a bunch of different inputs to make that estimate. You have used 2 quarts in 3000 miles, that is about 1500 per quart and that is not too bad. Once you start driving your engine and doing some WOTs, that should improve

Here is a description of the oil life monitor (OLM)

here is EVERYTHING you wanted to know about the OLM, by the GURU... Please understand that this may be confusing as I have copied MANY of his OLM posts from different threads! He is THE MAN...Mike

***************************************************************************

One thing I can touch on and clear up.....the GM oil life monitor operation and my statement that ZDP (or ZDDP as you tend to call it here...most of the API literature just sticks to ZDP so I tend to use that) depletion is the basis for oil deterioration.

My spelling is poor but ZDP stands for zinc dialkyldithiophosphate which , as it sounds, is an anti-wear compound comprised of zinc and phosphorus.

ZDP is dispersed in the oil so as to be at a potential wear site if a surface asperity happens to break thru the oil film thickness causing the dreaded metal-to-metal contact. A molecule of ZDP must be present at that moment to prevent microwelding at the contact site which will cause material transfer, scuffing, scoring, wear and catostrophic failure. The concentration of ZDP in the oil will determine if there is ZDP present to work it's magic. The greater the concentration...the more likely a molecule of ZDP will be there...and vice versa.

By nature, ZDP is sacrifical. As ZDP is "used up" at a wear site to prevent micorwelding the concentration of ZDP decreases.... So...if you measure the ZDP concentration in engine oil in a running engine it will decrease at linear rate based on engine revolutions. Any given engine has a certain number of high potential wear areas where metal-to-metal contact could occur due to reduced film thickness and/or surface asperities....areas such as rubbing element cam followers, distributor gears, rocker arm pivots, push rod tips, etc...... The more of these areas the more ZDP depletion. The more often these features come in contact the greater the ZDP depletion. That is why, generally speaking, ZDP concentration in the oil, for any given engine, will decrease at a fairly linear rate when plotted versus cummulative engine revolutions. The more times it turns the more contact the more chance for wear the greater the depletion. This is as much of a fact as I could quote ever and is really not speculation or anything. It is proven beyond a shadow of a doubt in many studies. That is why it is ONE of the basis for determining oil life remaining and why it is THE basic premis of the GM oil life algorithm. It is only ONE of the things that determines oil life...but it is the one thing that can be tied to engine operation in a linear fashion and estimated very accurately by accumulating engine revolutions via a counter.

The GM engine oil life monitor counts engine revolutions and accumulates the number for the basis of the oil life calculation. It then adds deterioration factors for operating temperature, start up temperature, soak times, ambient, coolant temperature, etc... There are a LOT of factors that "adjust" or affect the slope of the deterioration but the fundamental deterioration is traced back to the ZDP depletion that is inescapable with engine revolutions. The specific rate of ZDP depletion is readily measurable for any given engine so that is the fundamental item that is first calibrated for the oil life algorithm to tailor it specifically to that engine.

You would obviously like to get the oil out of the engine before the ZDP concentration gets so low that it is ineffective at being at the right place at the right time and preventing engine wear so that becomes the long term limit on oil life for that application.

The other things that determine oil life such a acid build up, oxidation, petane insuluables such as silicon from dust/dirt, carbon or soot build up from the EGR in blowby, water contamination, fuel contamination, etc.... are all modeled by the multipliers or deterioration factors that "adjust" the immediate slope of the line defined by the engine revolution counter as those items can be modeled in other ways and accounted for in the immediate slope of the ZDP depletion line.

The algorithm was developed over the course of many years by several lubrication experts at GM Fuels and Lubes, spearheaded by Doctor Shirley Schwartz who holds the patents (with GM) for the algorithm and the oil life montitor. I had the luck of working directly with Dr. Schwartz when the idea of the oil life monitor first progressed from the theoretical/lab stage to real world testing/development/validation. There were fleets of cars operated under all conditions that deteriorate the oil life for any and every reason and , thru oil sampling and detailed analysis of the oil condition, the algorithm was developed, fine tuned and validated to be the most accurate way invented yet to recommend an oil change interval by. As just one example, I have seen cars driven side-by-side on trips, one towing a trailer and one not, for instance, to prove the effectiveness of the oil life monitor in deteriorating the oil at a faster rate just because of the higher load, higher average RPM, higher temps, etc...and it works flawlessly.

The oil life monitor is so effective because: it is customized for that specific vehicle/engine, it takes everything into account that deteriorates the oil, it is ALWAYS working so as to take into account THAT INDIVIDUALS driving schedule, and it tailors the oil change to that schedule and predicts, on an ongoing basis, the oil life remaining so that that specific individual can plan an oil change accordingly. No other system can do this that effectively.

One thing is that I know personally from years of testing and thousands of oil analysis that the oil life algorithm works. There is simply no argument to the contrary. If you don't believe me, fine, but, trust me, it works. It is accurate because it has been calibrated for each specific engine it is installed on and there is considerable testing and validation of the oil life monitor on that specific application. NOt something that oil companies or Amsoil do. They generalize....the oil life monitor is very specific for that application.

Oil condition sensors in some BMW and Mercedes products are useful, also. They have their limitations, though, as they can be blind to some contaminates and can, themselves, be contaminated by certain markers or constituents of certain engine oils. Oil condition sensors can only react to the specific oil at that moment and they add complexity, cost and another potential item to fail. One other beauty of the GM oil life monitor is that it is all software and does not add any mechanical complexity, mass, wiring or potential failure mechanism.

There is considerable safety factor in the GM oil life monitor. Typically, I would say, there is a 2:1 safety factor in the slope of the ZDP depletion curve....in other words, zero percent oil life per the ZDP depletion is not zero ZDP but twice the concentration of ZDP considered critical for THAT engine to operate under all conditions reliably with no wear. This is always a subject of discussion as to just how low do you want the ZDP to get before the oil is "worn out" if this is the deciding factor for oil life. We would tend to be on the conservative side. If the oil life is counting down on a slope that would recommend a 10K change interval then there is probably 20K oil life before the ZDP is catostrophically depleted....not that you would want to go there...but reason why many people are successful in running those change intervals.

Please...NOT ALL ENGINES ARE THE SAME. The example above is an excellent practical justification of why you would want to add EOS and change the 15W40 Delvac in the muscle car at 3000 miles max and yet can run the Northstar to 12500 easily on conventional oil. You must treat each engine and situation differently and what applies to one does not retroactively apply to others. This is where Amsoil falls short in my book by proposing long change intervals in most everything if you use their oil. It just doesn't work that way. You can run the Amsoil to 12500 with no concerns whatsoever in the late model Northstar because even the oil life monitor tells you that for conventional oil off the shelf. Would I do that to the 502 in my 66 Chevelle...NO WAY. Amsoil says I can though. Wrong.

There are entire SAE papers written on the GM oil life monitor and one could write a book on it so it is hard to touch on all aspects of it in a single post. Hopefully we hit the high spots. Realize that a GREAT deal of time, work and energy went into developing the oil life monitor and it has received acclaim from engineering organizations, petroleum organizations, environmental groups all across the board. It is not some widget invented in a week and tacked onto the car.

The oil life monitor is not under the control of a summer intern at GM Powertrain per an earlier post....LOL Not that a summer intern wasn't compiling calibrations or doing a project on it but is under control of the lube group with a variety of engineers directly responsible that have immediate responsibility for the different engine families and engine groups. The idea that a summer intern was responsible for or handling the oil life monitor is ludicrous.....LOL LOL LOL

[CarlaValentine]

Well, being that I had to disconnect my battery to change my spark plugs, my OLM has been reset. Do you think it would be ok to base my next oil change on the fact that it was at 43%, so when it reaches 57% this time around, it would technically be at 0?

[adallak]

Well, being that I had to disconnect my battery to change my spark plugs, my OLM has been reset. Do you think it would be ok to base my next oil change on the fact that it was at 43%, so when it reaches 57% this time around, it would technically be at 0?

It might be different, but in my 91 Seville disconnecting the battery did not affect OLM.

[BodybyFisher]

Well, being that I had to disconnect my battery to change my spark plugs, my OLM has been reset. Do you think it would be ok to base my next oil change on the fact that it was at 43%, so when it reaches 57% this time around, it would technically be at 0?

Check it again, I dont think it should be reset as Adallak mentioned.

[Cadillac Jim]

I wouldn't run it down to 0. You start get messages on the dashboard at 10%, I believe. I'm a maintenance nut, so I never let mine get much below 40%.

[KHE]

I don't think all Northstars leak - my '97 STS is bone dry underneath at 152,109 miles - no leaks whatsoever. My '05 Deville is also leak free - but it should be at 5 years old and 42,000 miles. My '96 Seville is leaking at the oil manifold plate.

[CarlaValentine]

Well, being that I had to disconnect my battery to change my spark plugs, my OLM has been reset. Do you think it would be ok to base my next oil change on the fact that it was at 43%, so when it reaches 57% this time around, it would technically be at 0?

Check it again, I dont think it should be reset as Adallak mentioned.

It definitely reset itself. I had disconnected both battery terminals, due to my having to pull off the ICM and I have an overwhelming (some say neurotic, but if you've been bitten by a 440v breaker box, you would too) fear of electricity. After I reconnected everything and started the car for the first time, the SES light came on. When I ran the codes, I got:

P032: Open MAP sensor signal (STILL...I have looked EVERYWHERE and still can't find a stupid vacuum leak)

P052: PCM Memory reset

P109: Keep alive memory reset/PCM has lost primary battery power

When I ran through everything on the DIC, the oil life monitor was at 100%. Strange that would reset, but the odometer wouldn't...I'd imagine they run off the same memory....

[Ranger]

I agree with Kevin. My '97 leaked and the halfcase was replaced under warranty. It was bone dry when I sold it at 107K. My daughters '99 was dry when she sold it at 40K. She bought my '02 and it is still dry at 40K as is my '03 at 77K. I think the halfcase seal was redesigned.

Carla, I think your math is correct. If it reset, change it when you get to about 60% or so.

[Texas Jim]

P032: Open MAP sensor signal (STILL...I have looked EVERYWHERE and still can't find a stupid vacuum leak)

P052: PCM Memory reset

P109: Keep alive memory reset/PCM has lost primary battery power

When I ran through everything on the DIC, the oil life monitor was at 100%.

Strange that would reset, but the odometer wouldn't...I'd imagine they run off the same memory....

The odometer retains the mileage in the Instrument Panel Cluster.

It is non volatile memory... it can not be changed without special tools and equipment.

The memory in the DIC "IS" volatile memory, which can be changed.

[CarlaValentine]

P032: Open MAP sensor signal (STILL...I have looked EVERYWHERE and still can't find a stupid vacuum leak)

P052: PCM Memory reset

P109: Keep alive memory reset/PCM has lost primary battery power

When I ran through everything on the DIC, the oil life monitor was at 100%.

Strange that would reset, but the odometer wouldn't...I'd imagine they run off the same memory....

The odometer retains the mileage in the Instrument Panel Cluster.

It is non volatile memory... it can not be changed without special tools and equipment.

The memory in the DIC "IS" volatile memory, which can be changed.

I knew that, but didn't think about it...point taken. lol. I feel kinda dumb sometimes.

[Texas Jim]

P032: Open MAP sensor signal (STILL...I have looked EVERYWHERE and still can't find a stupid vacuum leak)

P052: PCM Memory reset

P109: Keep alive memory reset/PCM has lost primary battery power

When I ran through everything on the DIC, the oil life monitor was at 100%.

Strange that would reset, but the odometer wouldn't...I'd imagine they run off the same memory....

The odometer retains the mileage in the Instrument Panel Cluster.

It is non volatile memory... it can not be changed without special tools and equipment.

The memory in the DIC "IS" volatile memory, which can be changed.

I knew that, but didn't think about it...point taken. lol. I feel kinda dumb sometimes.

Well, at least you are only SOMETIMES...I am that way MOST OF THE TIME.

[Cadillac Jim]

Open MAP sensor signal doesn't mean a vacuum leak. It means that the Manifold Air Pressure (MAP) sensor connector is loose or off. The MAP sensor is under the beauty cover on the intake manifold near the throttle body. Pull off the connector (if it's on), clean or tighten the contacts if necessary, clean the contacts on the MAP sensor, and plug it back in. Put the beauty cover back on and that code is history.

I had that problem years ago and was ready to buy a new MAP sensor. It just pops out, and I had it in my hand ready to make a run to the dealer, and was looking at it. Nothing wrong here to the eye -- why not just try it again, I thought, so I popped it back in, put everything back together, and never had another problem. Apparently the contacts got dirty when I had the fuel rail recall work done a few months earlier.

[CarlaValentine]

Open MAP sensor signal doesn't mean a vacuum leak. It means that the Manifold Air Pressure (MAP) sensor connector is loose or off. The MAP sensor is under the beauty cover on the intake manifold near the throttle body. Pull off the connector (if it's on), clean or tighten the contacts if necessary, clean the contacts on the MAP sensor, and plug it back in. Put the beauty cover back on and that code is history.

I had that problem years ago and was ready to buy a new MAP sensor. It just pops out, and I had it in my hand ready to make a run to the dealer, and was looking at it. Nothing wrong here to the eye -- why not just try it again, I thought, so I popped it back in, put everything back together, and never had another problem. Apparently the contacts got dirty when I had the fuel rail recall work done a few months earlier.

About the MAP sensor thing...it's a vacuum leak, somewhere. See my other post.

http://caddyinfo.ipbhost.com/index.php?sho...mp;#entry159932

[CoupeDTS]

Well we made the trade last night. I wanted to atleast educate the dealers and manager there on the confusing "midseal" that they speak of but only one of the dealers was there and the manager. The dealer seemed to listen and I convinced him it really could be the oil filter adapter. The manager was another story.

Someone on this topic said if I did educate them it would give them the satisfaction that they were right, thats pretty much what happened. I explained it to him so that he wouldnt confuse and piss off customers as he did I. He said ok but I just want you to know we werent screwing with you its a real leak and we have came in contact with it too many times and customers bring the cars back and we are out the money to fix them or a loss of reputation. I said fine but it ALSO might not even be that "seeping" it could be the oil filter adapter, he said the oil he seen wasnt by that filter so it couldnt be that and I blew that off because i doubt he knows where the filter is in the first place and anyone knows if you have a leak EVERYTHING gets wet on the bottom around that leak. Then he just said his basic thanks for your business and walked off. He didnt care, it was obvious.

Now we just have to see if its washed and on the lot today or tomorrow. Supposedly they are going to sell it at auction today but well see.

[Texas Jim]

What did you trade it for?

[CoupeDTS]

What did you trade it for?

LOL sorry i guess i havent even included that.

My wife has been driving my DTS so its kind of what she wanted with my input included. We got a 05 Buick Rainier SUV. They are like the trailblazers/envoys but the Buick version. She wanted all wheel drive and an SUV just not the giant SUVs. I like it because its GM, has very nice woodgrain, leather and chrome interior like cadillacs, also great styling outside, and a plus for me was the chevy engine. Another thing I love is a nice ride, this Buick comes with the luxury soft suspension with the air ride on the back, so it rides very similar to my DTS in an SUV! Alot of SUVs ride rough from their off road suspension but 2% of people really take them off road, i hate that! Those engines they use in there are a common dependable motor that if something should happen I can work on a little easier or cheaper than the northstars.

Its a 1 owner vehicle, always serviced at the dealer even for oil changes so its very clean. The buick version of that truck are very rare, you mainly see rendevous around, you can see on ebay there are only 5 of these Rainier's for sale nationwide so they are fairly limited. Im now a member of trailvoy.com forums to get info on this truck.

But Ill never get rid of my other caddys, there will only be more My grandpa bought new buicks every few years since the 1940s and our family has always been a GM family, they have some pride in knowing I continue the tradition. And to me this Buick is just as nice as any caddy.

Its funny I just thought about it, the Buick has a Chevy motor in it, my Fleetwood has a Chevy LT1, and my 83 coupe Deville I put a Chevy 350 in. All chevy motors lol.

[Texas Jim]

Very nice...hope you have many, many miles of trouble free driving.

I have a Sister-in-Law that only drives Buick SUV's.

She gets one every 3 years or so.

[CoupeDTS]

Very nice...hope you have many, many miles of trouble free driving.

I have a Sister-in-Law that only drives Buick SUV's.

She gets one every 3 years or so.

I only seen rendevous (like equinox, torrent) and the rainier's. I think they make the enclave now? We test drove a SRX but it just didnt feel like a caddy to me. It has a northstar and cadillac badging but the seats are hard, the instruments all have an orange glow, it just felt like a catera/german like design to me. Maybe its just not the super plush luxury like i like i dont know. Plus my wife said it looks like a station wagon. I admit it does, its as tall as a durango or midsize SUV but it looks like a car like body thats just raised a foot off the ground. You really have to step down out of them but it seems like a car. We just werent feeling em, coulda got one for about the same price as the Buick but I dont know what Cadillac is thinking making those things....

[PAUL T]

I bought my 94 Concours with an oil leak, not knowing at the time what it might be. After my education from this board and the cost of the repair I just added oil. I drove it over 100,000 miles this way, just added a quart and a half everytime the check oil light came on. I would still be driving it if the headbolts had not pulled. It is a parts car for my 97 Deville for now, RIP.

[CarlaValentine]

I'm just wondering, how low is the oil supposed to be able to get before the "check oil" light comes on?

[Bruce Nunnally]

As I recall on the NS 1.5 quarts below 'low'.

[Ranger]

I'm just wondering, how low is the oil supposed to be able to get before the "check oil" light comes on?

2 qts low leaving 5.5 qts in the sump. It comes on just about the time the oil level drops off the dipstick.

[CarlaValentine]

Mine's never been more than a quart or so low, which would explain why my light has never come on. I thought maybe it wasn't working....I guess it just hasn't been that low.

A car I had before would have the oil light come on if it was about half a quart low or so, so I thought this one would be the same. I didn't take into account that this engine holds a little over 7 quarts all together.