Thread: Bad knock at start up

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  1. #1 Bad knock at start up 
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    Hey
    I've got a serious problem with my cars start up. The car will now on occasion on start up have a very loud knock that lasts anywhere from 30 sec to 5 min. Had gone away every time but am wondering whether it's fixable? The first time I checked it was low a quart of oil ( not the first time but had been running great the day before) so I filled it up and it seemed to help. Now the second time today when it happened you could actually smell oil burning. Noise went away and once it warmed up the car started back up fine. Could it be an oil sending unit or something with a cold start issue?

    The car has 373,000 kms but I love the car and have done way to much to it to give up on it. Any help would be super appreciated.
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  2. #2 Re: Bad knock at start up 
    Killa Bee Scottydoggs's Avatar
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    post a vid, sound like rocker clap due to a lifter that lost pressure over night.

    when was your last oil change? going way over due used make my car make a rocker clap sounds. change the oil and no more sounds.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  3. #3 Re: Bad knock at start up 
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    I had the oil changed about 3000 km ago. And yea it does sound like it's coming from the valves. And I'm not sure about the rocker clap part. Was planning on doing an early oil change and adding Lucas oil additive to it.
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  4. #4 Re: Bad knock at start up 
    Killa Bee Scottydoggs's Avatar
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    rocker clap is what you hear when the lifter fails to hold its pressure, the lifter pushes the push rod, that pushes the rocker arm.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  5. #5 Re: Bad knock at start up 
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    I watched some videos on it and it's the same sound as mine. Except mine doesn't continue to stay loud, it eventually goes away. If I were to remove the valve covers to inspect the valve train, what all do I need to remove to get at then(intake manifold fuel rails) and would gaskets for the intake be a good idea to get agin? I replaced the intake 2 years ago. So I've got a little bit of an understanding of under my hood.
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  6. #6 Re: Bad knock at start up 
    Killa Bee Scottydoggs's Avatar
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    truth is, Gm says its ok as long as it stops in a few minutes after a cold start.

    valve covers come off pretty easy, just the strut mount aka dog bone mount needs to come off on the front. taking the rail off iirc makes getting to the mounts bolts easier.

    you n/a guys, i dont think theres much of anything blocking the rear cover.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  7. #7 Re: Bad knock at start up 
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    Awesome hopefully the winter won't hurt it to bad. And yea I plan on doing a oil change and adding a quart of synthetic to help the oil out. It's just a winter beater but it's my first car and it's been pretty awesome for the last 4 years
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