Bent pushrod - valvetrain noise ?
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Northstar Engines and System Technical Discussion Discussion, Bent pushrod - valvetrain noise ? in Cadillac Engine Technical Discussion; I have 205k miles on my 97 sts and I believe I had the unfourtantly event of getting a bent ...
  1. #1
    Sparkyy's Avatar
    Sparkyy is offline Cadillac Owners Member
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    Bent pushrod - valvetrain noise ?

    I have 205k miles on my 97 sts and I believe I had the unfourtantly event of getting a bent pushrod on the ride home from work after passing someone? Is there any quick fixes and what's the life expectancy of the motor now. I drive easily but I do drive it for sure sometimes

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    dkozloski's Avatar
    dkozloski is online now Cadillac Owners 10000+ Posts
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    Re: Bent pushrod.

    It's a pretty neat trick to bend a pushrod in a DOHC motor that doesn't have them.
    Don't mess with Binky Bear!


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    Sparkyy's Avatar
    Sparkyy is offline Cadillac Owners Member
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    I have a nice knocking noise coming from one if the heads, any idea what it might be. It was a little low on oil and I added a quart but I do that once a week as it is

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    Re: Bent pushrod.

    Broken valve spring?
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    Sparkyy's Avatar
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    Yes I believe that's what it is now, I'm having the car looked at today to find out and thank yall

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    Faded Crest's Avatar
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    Re: Bent pushrod.

    I also heard of someone having a broken cam bolt on their N*, but broken valve spring is more likely.

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    Aztec ETC ECS's Avatar
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    Re: Bent pushrod.

    I think if a valve spring broke, it would have sucked a valve & BLEW UP. Could be broken cam bolt. Or just plain worn out at 205K. Wrist pin knock? Sometimes hard to pinpoint noise.

  9. #8
    johnny kannapo's Avatar
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    Re: Bent pushrod.

    Most likely would be cam lobe wear due to a failed valve bucket contact surface.
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    mike5514 is offline Cadillac Owners Enthusiast
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    Re: Bent pushrod.

    I had a tapping noise on my 97 turned into a knock put in a blue 16 oz. bottle of a zinc additive tap/knock gone. Worth a shot couple of bucks.Mike

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    johnny kannapo's Avatar
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    Re: Bent pushrod.

    Maybe so, if there is a tapping in this engine I would have a hard time believing a bottle of zddp is going to help.
    Nothing can get stuck in the valve train unless a valve was stuck in a guide.

    Stuck guides would have a difficult time getting oil to then.
    I don't think anyone here has ever posted stuck valve problem in this forum.
    I suppose that could happen but it would run rough & pop out the exhaust or intake which would blow off the back fire valve.

    If you know where in the head the noise is, to check for piston/rod problem pull a plug wires to see if the noise lessens.
    If the noise is on the Trans end of the engine It could be associated with the Trans. Flex plate for example maybe coming apart.
    It can be tricky pin pointing knocks.

  12. #11
    mike5514 is offline Cadillac Owners Enthusiast
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    Re: Bent pushrod.

    Don't remember how long ago I added zddp but I went out yesterday the 97 has been sitting for about a week and I opened the hood started the car got back out and listened to the engine no tap no knock just typical N coming off fast idle.

    The other day I picked up some Quaker State Defy 5 quart big letters on the jug zddp added for high mileage engines. Leads me to believe the removal of zddp is/or was not a gov./epa. thing it was the oil companies that decided to remove it. If Quaker State feels there might be a market for it there might be something to it.

    My dts has 90000 miles on it and I think I will be using the QS with my next oil change. I haven't used QS in years I have been using Havoline/Chevron but if the new QS keeps my Ns from ticking or knocking it might be a keeper.Mike

  13. #12
    naif is offline Cadillac Owners Connoisseur
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    Re: Bent pushrod.

    ZDDP was removed because it can poison catalytic converters if there's enough oil burned - making the cost of the required 100,000 mile (in some places) emissions warranty worth the added expense of designing in no high-sliding-friction areas (flat tappets).

  14. #13
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    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Bent pushrod.

    mike, take a look at the oils and spec sheets from Shell and Pennzoil also - in addition to Quaker State they're refined and packaged by the same company - SOPUS (Shell Oil Products U. S.)

    Yes, excessive ZDDP will ruin a cat, but ZDDP has not been removed from starburst oils used in automobile engines - it has been reduced in percentage by volume. Ranger recently posted a table of ZDDP levels for the last ?? 20 ?? years of oil API specifications - from SF to SM, I believe.

    Because ZDDP contains phosphorus and zinc, the EPA is the driving force behind its reduction in motor oils - same reasons why phosphorus is being phased out of dishwasher and laundry detergents: California's (and, by default, Big Brother's) fear of excessive human ingestion of perceived nasties.

    If SF and SG oils were perfectly fine for catalytic converters ~15 years ago, they would be just fine right now.

    Here's one reference of hundreds - Google "api oil service designation".

    http://en.wikipedia.org/wiki/Motor_oil

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    naif is offline Cadillac Owners Connoisseur
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    Re: Bent pushrod.

    15 years ago there wasn't such long required warranties on emissions...

    Yes, I meant to say reduced, not sure how it came out as removed

  16. #15
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    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Bent pushrod - valvetrain noise ?

    Yeah, that ^^^^

    I'm gonna move this thread to Northstar and give the engine gearheads a shot at diagnosis -

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