Intake Valve Problem!
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Intake Valve Problem! in Past Cadillac Vehicle Discussion; I've got a 1997 Eldorado that lost compression on number 8. A leakdown test revealed that it was losing compression ...
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    Jims_97_ETC's Avatar
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    Intake Valve Problem!

    I've got a 1997 Eldorado that lost compression on number 8. A leakdown test revealed that it was losing compression through the intake. It is a Jasper with 45,000 miles on it, six years old (no warranty!!!!!) Has anyone ever heard of such as thing? How does an intake valve just go bad on a Northstar?

    No codes other than P0300 for the bad cylinder at cold idle, no oil or coolant usage for the six years the Jasper has been in the car, no oil leaks other than a minor seep in the front seal. Immaculately maintained, driven regularly, oil is always Mobil 1 5W-30, always run 92/93 octane top-tier gas.

    Also, any advice on pulling the front head with the engine in the car is welcome.
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    Re: Intake Valve Problem!

    The pre-2000 Northstars use hydraulic 'bucket' cam followers (lifters). Occasionally the case hardening on the bucket face wears through and the valve spring/keepers/bucket fails. This MAY be your case. Unfortunately, disassembly is tedious and specialized - there are hoops to jump through with timing chains, sprockets, tensioners, and cam removal (water pump drive pulley and seal).

    You will NEED a GM/helm service manual and some decent tools as well as a mechanical eye for detail.

    Google "cadillac forums northstar hydraulic lifter failure" for a lot of reading.
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    Re: Intake Valve Problem!

    First time I've heard of anything like this.
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    Re: Intake Valve Problem!

    Find the pictures of a pre-2000 Northstar overhaul - several in the series show a few TOTALLY destroyed cam follower buckets and rounded off cam lobes - two buckets eaten clear through to the valve stem tip itself. In the same thread was a discussion about the bucket face hardening process. The thread also discussed the wisdom of using HD Fleet and Marine multigrade oils in flat tappet engines.
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    Re: Intake Valve Problem!

    Wow, Sub, you and Ranger are God sent.
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    Re: Intake Valve Problem!

    Where have you been lately ??? Nothing has changed one bit - it's all still in here from 2003-on.
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    Re: Intake Valve Problem!

    I'm great, hope you are as well. I love to drop back in this lounge to see what's new or old. You and Ranger have always been great to this lounge. I always learn something from you guys.
    Tankboy40 and Tankboy40 like this.
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    Re: Intake Valve Problem!

    The engine is a Jasper remanufactured motor with only 45,000 miles on it. The car is driven nearly every day and it has always had Mobil 1 5W-30 in it and nothing else. Except for a half-tank as Sandy approached landfall it has always had 92/93 octane top-tier gas. I'm familiar with lifter bucket failure from the early big-block bow-tie days, and determined that this problem is usually seen only on high mileage engines or cars that don't get regular oil changes, or both. I bought one used, once, that had that problem and heard of others. This car has neither in its history. So, whatever it is, it's a rare problem.

    The lifter bucket issue is one that has occurred to me. I recently read an article that said that 20% of valve failures in modern engines are due to metallurgical failures in the valves themselves. How many are due to metallurgical failures in the lifter buckets?

    As to how a bad lifter can cause a compression leak into the intake, well, I can hazard a guess there. If the lifter stops turning, the valve stops turning. But, this car does not have a performance or economy problem, or any significant engine noise - but there has been a lifter noise when cold from the time the engine was a few months old. It appeared gradually, got pretty noticeable and even was audible from a hot engine after about a year, but has lessened with the years. Perhaps this lifter has taken a set and stopped rotating.

    This is great. Any other comments from those who have known a lot of 1993-1999 Northstars?
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    Re: Intake Valve Problem!

    That is the WRONG oil to use for a '97 N*. Up to (including) '99 the engines suppose to use 10W30.
    Not that it will have any relation with the valve seat issue you suspect, but could eat the lifter (yet it will not leak because of the lifter, it will do the opposite, not open far enough).
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    Re: Intake Valve Problem!

    Quote Originally Posted by N*Caddy View Post
    That is the WRONG oil to use for a '97 N*. Up to (including) '99 the engines suppose to use 10W30.
    Not that it will have any relation with the valve seat issue you suspect, but could eat the lifter (yet it will not leak because of the lifter, it will do the opposite, not open far enough).
    That "could" be part of the problem, but I still don't recall hearing much about this before.


    Quote Originally Posted by Submariner409 View Post
    Where have you been lately ???
    I was about to say the same thing. Where the hell have you been Al?
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    Re: Intake Valve Problem!

    I've been busy trying to keep my head above water. I still have the Eldo but it's been in storage for awhile. I intended to change out all of the hoses and get it back in shape. Sorry Jims_97_ETC. I didn't mean to derail your thread.
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    Re: Intake Valve Problem!

    Cadillac and GM have been recommending Mobil 1 5W-30 for my car and others like it since 1999. I had it serviced almost 100% at the dealer until about 2004 and that's what they put in it. The original engine had no valve or lifter problems in spite of going 116,500 miles on Mobil 1 5W-30. It pulled a head bolt. This engine has 45,000 miles on it. I change it at 40% on the OLM or less, sometimes at 3,000 miles or 50% on the OLM (usually those happen together). Whatever your opinions are on oil, I don't think that the oil caused this one.

    ----------

    The only Northstar teardown photo I have found here that includes a photo of the lifters is here. The lifters look good. His problem was a blown head gasket.
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    GM never recommended synthetic for these cars, and your oil change intervals are just wasting oil and money.
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    Re: Intake Valve Problem!

    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.
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    Re: Intake Valve Problem!

    Wow, 2 dealers?
    There is good reading in the N* technical section about the N* cylinder design and cross hatch pattern which clearly explains why synthetics are not recommended. It's the first time I've ever heard of a designed Quart/Miles ratio for oil usage in ANY engine.
    Learn something new everyday if I try.
    Taz
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