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Cadillac Seville / Cadillac Eldorado Forum Discussion, Intake Valve Problem! in Past Cadillac Vehicle Discussion; Before anyone hangs their hat on "information" in that ^^^ post, read and study the two pertinent articles in the ...
  1. #16
    Submariner409's Avatar
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    Re: Intake Valve Problem!

    Before anyone hangs their hat on "information" in that ^^^ post, read and study the two pertinent articles in the Cadillac Technical Archive......... again: study it, don't simply skim it. Nowhere does it say that synthetics are not recommended, and it might be instructional to read the owner's manuals from some post-2004 powered cars.

    FWIW, "oil consumption" is a design consideration in every internal combustion engine built. (How far would a B-17 fly before it ran out of engine oil ?)
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  2. #17
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    Re: Intake Valve Problem!

    My bad. I used the wrong "R" word. From the archive...it states "Not Required".
    "Use conventional mineral oil (synthetic is not required at all) as it tends to provide better oil consumption."
    Also to note:
    "The single biggest variable and the one that has been discussed at great length on this forum is the cylinder bore finish or the cylinder honing pattern. The higher performance the engine is the more attention must be paid to the honing pattern and retention of oil on the cylinder walls to lubricate the piston and rings at full load , high RPM operation. The Northstar engine uses a very aggressive cylinder bore finish that tends to retain a lot of oil to protect the piston and rings."
    Hang your hat on it or not. Someone else wrote it and someone else decided it was noteworthy to place in the archives.
    I plan on staying with conventional oil. An agressive hatch pattern and more oil retention on the cylinder walls = more oil in the combusiton chamber. I'd rather burn mineral based oil than a synthetic.
    My .02
    Taz
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  3. #18
    N*Caddy's Avatar
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    Re: Intake Valve Problem!

    Quote Originally Posted by Jims_97_ETC View Post
    Two Cadillac dealers on two coasts recommended Mobil 1 5W-30 for my car and put it in regularly. You are correct that I changed my oil too often. There are others who will say that using modern oils with less ZDDP requires more frequent oil changes on cam-on-lifter-bucket engines. All of that belongs on an oil thread. My point here is that the car wasn't neglected and the engine is low mileage, and reman, not a rebuild.

    The only pictures of the valve lifters that I can find on this forum are here, in topic 270955, started by maeng9981 on 09-27-12 at 5:35 AM EDT. Look at post #10, pictures four and six, for a view of the top of the head. Picture four shows the lifters on the valves on the intake side and picture five shows a close-up of the two lifters on the back end of the head. Picture six shows that the lifter gallery breaks through the lifter bore as it passes each lifter. About half the oil that flows to each lifter from the lifter gallery flows above the lifter to the bucket area and half flows down to the valve spring/valve guide area.

    Just so is clear Cadillac switched to 5W30 for the N* engines manufactured after '00 (the design change), not starting with the '00 for all N* engines.
    So not the date when you change the oil matter to determine what kind of oil to use, the date when the ENGINE WAS MANUFACTURED!
    Let me make it very easy for you, if your engine has coil on spark then it needs 5W30, if it has coil pack and ignition wires then it needs 10W30 al year round (or if you are in Alaska in winter you can use 5W30). There is a clear chart in the owner's manual with what kind of oil to use how the temperature matters in this choice. But for your location you should never need to use 5W30.
    And if that was not clear enough, is indicated on the oil cap for God's sake what oil you need to use (unless you don't have the correct oil cap).
    The people working at the GM dealership are not rocket scientists, not even near that. I know mechanics using the same kind of oil in all cars just because that is the only kind of oil they have (is cheap to buy a drum of one kind of oil vs. 1 drum of each kind of oil).

    So again if I was not clear YOU ARE USING THE WRONG OIL TYPE for the engine (unless your engine has roller cam followers - and you know that if you have coil on spark, not coil pack and ignition wires). Also '00 is the year when the engine design was changed not '99. don't try to correct me on this I am right.
    Your engine may be rebuilt and may as well have a date on it of 2013, that's not important, important what kind of design is, 99 or older or '00 and newer.

    This engine is a '00+ design and requires 5W30


    This engine is a '99 or older design and required 10W30


    Based on the engine cover and spark plug wire routings I can tell the above engine is manufactured between '94 and '99, based on the AC line I can tell you the engine is manufactured before March '97 and based on the brake fluid reservoir I can tell you it is a '94-'95 engine and finally based on the intake box/duct I can tell you this is actually a '94 or very early '95 engine. But that's not important, the same thing applies for all '92-'99 engines.

    Like I mentioned, 5W30 or 10W30 has no effect on the valve seat, a worn cam becomes shorter, thus opens less, but will not leak at compression.
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    Re: Intake Valve Problem!

    That looks like a '95 here's My '94

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    Re: Intake Valve Problem!

    '93 & '94 where all by themselves. Your intake cover is functional. Intake manifolds where changed in '95, so '95 to '99 looked the same. In 2000 they lost the ICM and plug wires.
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  6. #21
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    Re: Intake Valve Problem!

    Actually, '95 stands alone, it received the revised intake and 5 hp boost, but retains the obd1.
    93-94 doesn't share the same PCV location. Dash started to change in 96...N*Caddy can enlighten additional changes thereafter. Actually they changed in one way or another every single year!
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  7. #22
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    Re: Intake Valve Problem!

    Meaningless oil arguments won't get us anywhere. People who want to say that others can't tell the difference between a 1995-1999 Northstar won't get us anywhere. People who want to say that people at dealerships make maintenance recommendations to people with cars in warranty on their own without input or traceability of their data to GM won't get us anywhere.

    The recommendation of 5W-30 Mobil 1 was for "improvements in fuel economy" as it was explained to me. My previous car had a Quad 4 HO. That engine had noticeably more snap and noticeably more punch at redline with 5W-30 Mobil 1 than it did with 10W-30 Mobil1 or dino oil 5W-30. My 1997 ETC allowed 5W-30 Mobil 1 from Day 1 as a GM suggestion for better fuel economy and I could feel the difference in performance even with the 4.6. Once they put dino oil in my car at the dealer by accident, and I could tell instantly when I started it. I called the service manager over and asked her to check it and they changed it again free.

    Anyone who thinks that conservative oil change intervals with 5W-30 Mobil 1 could cause a compression problem in 45,000 miles, please hold up their hands. Thank you.

    Now, back to the question. what might have caused this? The best guesses that I have seen are a metallurgical problem in the valve itself, or possibly in a lifter bucket.

    The head is coming off about now. The problem isn't bad enough to be likely to be visible unless there is a radial crack in a valve or some such. The machine shop will likely be the one that gives the answer.

    What I have found in the week that this topic has been up is that this is a vanishingly rare problem. The only examples that people have come up with are old, high-mileage, poorly-maintained motors that can and do have any problem. I don't think anyone has an answer. I'll get back with this topic when I know more about this particular engine.
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  8. #23
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    Re: Intake Valve Problem!

    My previous car had a Quad 4 HO.
    That engine had noticeably more snap
    and noticeably more punch at redline
    with 5W-30 Mobil 1
    than it did with 10W-30 Mobil1 or dino oil 5W-30

    and this NOTICEABLE difference was of course DOCUMENTED -
    by the ACME 5000 BUTT DYNO -

    My 1997 ETC allowed 5W-30 Mobil 1 from Day 1
    as a GM suggestion for better fuel economy
    and I could feel the difference in performance even with the 4.6

    another testimony on the complete accuracy -
    of the ACME 5000 BUTT DYNO -

    I'll get back with this topic when I know more about this particular engine.
    but PLEASE stop with the BUTT DYNO comparisons
    between 5w30 and 10w30 synthetics -
    it makes you sound silly -
    and you loose ALL credibility -

    the ONLY benefit to 5w30 would be starting -
    in below zero temperatures -
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  9. #24
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    Re: Intake Valve Problem!

    I keep mentioning, THE OIL USED HAS NO EFECT ON THE VALVE SEAT!!!!!!!!! You will ruin faster the lifters or the cam lobes (the diesel like noise)
    Fuel economy may be, and probably 0.1 HP gain, but the REASON pre '00 cars use 10W30 is the cam design.
    Please understand, I have nothing against you, I just try to give you a friendly advice, the people writing the Owner's Manual are engineers (so am I), the people working at a dealership may not even have complete high school education.
    Unless GM issues an official statement that 5W30 is now fully compatible with 10W30 you follow the owner's manual. A guy working at a dealership is not a official GM spokesman.
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  10. #25
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    Re: Intake Valve Problem!

    N*Caddy - at the risk of encouraging more off-topic oil wars, we have plenty of GM people here. Let's see if one of them chimes in, with GM-traceable information, that says that 5W-30 Mobil 1 isn't acceptable for 1997 VIN 9 Northstars. I can say that I have heard from many service managers and all GM dealers that I have been to in the last 15 1/2 years that 5W-30 Mobil 1 is the best premium alternative for my Northstar. I always used it on my original engine and it was fine, valve-wise, at 116,500 miles when I retired it for a head gasket problem. I needed the car every day so I did an engine exchange over the July 4 holiday in 2006 rather than go for a Timesert job - which at the time I did not have a mechanic willing to attempt.

    Advice is welcome. Taking the topic over for an oil war simply destroys the topic. And I am getting flames over the oil war now, not answers or suggestions about a rare intake valve problem.
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  11. #26
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    Re: Intake Valve Problem!

    My 97's manual says to use 10w-30, it was written by engineers, i stick to that...
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    Re: Intake Valve Problem!

    I do not recall the pre-2000 Northstars being spec'd for anything but 10W30. To the best of my knowledge they didn't get 5W30 until 2000 when GM went to the roller followers.
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  13. #28
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    Re: Intake Valve Problem!

    the manual (and the oil cap) says 10w30 but i'm pretty sure 5w30 is not a problem at all for the pre-2000 Northstars except in hot weather
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  14. #29
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    Re: Intake Valve Problem!

    How did a potentially stuck intake valve turn into an oil war ?

    Do some homework - it's all still in here somewhere - including the aggravated cam follower bucket face wear.

    https://www.google.com/search?q=cadi...w=1280&bih=633
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  15. #30
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    Re: Intake Valve Problem!

    You are located in mild weather, thus your '97 engine should use ALL YEAR ROUND 10W30. 5W30 is acceptable for pre '97 engine only in certain conditions (see the chart below):

    Sorry for the resolution, but you can find it in the owner's manual.
    10W30 should be used when the outside temperature is never lower than 0*F.
    5W30 should be used when the outside temperature is never higher than 60*F
    So between 0*F and 60*F either oil can be used, you can safely use 5W30 in the colder month of the winter.
    But you can safely use 10W30 all year round in your location.

    Please try to understand I am only advising you with good intention, I am also instructing you to take the advise of a service manager or what ever "experienced" mechanic with a grain of sand. If the information you receive is conflicting the owner's manual ask for a 2-nd, or 3-rd opinion.
    Yes a thinner oil is pumped easier thus you reduce some pumping resistance (gain even some 0.1 HP) but at the expense of wearing the cam followers and the cam lobes (not the cam seat) and the bearings and the rings/cylinders. Thinner oil will also increase the oil consumption (some remains on the cylinder walls and is burned because is not fully scraped by the piston rings). The engine was fully redesigned in 2000, this allowed the use of 5W30. It is a thread, it does provide some advantages, but in the engines specifically designed for it. Pre '00 engines were NOT designed for it.
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