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I have a 97 chevy 5.7 vortec it knocks when cold but goes away when it warms up my truck is running lean which is causing a few other problems and ive done some research and im getting it could be bearings on bottom end could be piston slap could be a collapsed lifter i cant tell if its coming from the top or bottom i have good oil pressure can anyone tell me for sure what its is

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  • Cars & Trucks Master
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All of the problems you mentioned will be there when warm. bearing noise gets worse as the oil thins out and the oil pressure will be lower than normal. Collapsed lifter will indicate with a problem misfiring and will be there all the time. Piston slap will be more evident at lower than required idle rpms. Some knocks can be from loose valve seat inserts but then again that will show up as an occasional misfire and will progressively get worse. Check that the oil filter you are using has a non-return valve built into it to retain oil in the top end when stationary. The knock may be until oil pressure is built up. El cheapo filters mostly do not have the valve. check the viscosity of the oil you are using as you may have to go up a grade.
use a mechanics stethoscope to pinpoint where the noise is coming from. Some failing bearings (idler,water pump,alternator etc) will knock for a while until they warm up

Posted on Nov 14, 2014

  • 3 more comments 
  • Josh j Nov 14, 2014

    I use a acdelco oil filter its last week i put a new tensior pully on because it was bad ive had my head all round that motor and cant figure it out knock goes away when warm but while its cold it knocks like crazy and the faster i go the louder it gets then truck warms up and it goes away ive talked to a bunch of people and no one has a definite answer i pulled the valve covers and eveything seems fine there i even replaced the knock sensor thinkin maybe that was causin it

  • Josh j Nov 14, 2014

    Is this fatal to the engine or can i let it go until i can afford a new motor

  • Bill Boyd Nov 15, 2014

    most people think that the way to fix is new (another motor) While it sounds bad the fact that it goes away indicates that it is repairable if you can find out the fault. This is done by using a good accredited mechanic in a specialist shop to diagnose the fault by running a series of tests ( compression test -oil pressure test- listening with the appropriate instruments and general knowledge of your engine make and model. Do not run out to throw money away until you know exactly what is the problem

  • Josh j Nov 15, 2014

    Thanks i definitely need to figure it out just dont have the cash to take to a mechanic right now which is why im tryin to figure it out on my own if i can

  • Josh j Nov 15, 2014

    Any suggestions as to what i can do


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Posted on Jan 02, 2017

james klgr
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SOURCE: experiencing a

it may need a lifter or valve adjustment when cold they will tick or knock depending on how loose or worn out then when it warms up they swell with heast and noise stops. after adjusting or replacing it will stop making noise

Posted on Oct 26, 2009

  • 27 Answers

SOURCE: How do you tell good lifter from bad lifters in 97

Most of the vortecs that i have worked on have hydraulic roller lifters, but i cant say for certain that your engine does, however i am sure that it has hydraulic lifters and they can be checked by trying to push them down in the center where the pushrods contact, if they compress easily the lifter is bad, If they are roller lifters, check for any wear on the roller and how well they turn, it is ok to have some side to side movement on the pin but any up/down movement on the roller is bad. If the are non-roller lifters check for wear, if the lifter looks "dished" or "concaved" rather than having flat surface replace the lifter.

Posted on Jan 23, 2010

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SOURCE: a knocking that starts when engine is cranked then it goes away

The knock is likely a worn connecting rod bearing. Are you using the correct weight of oil, never use any heavier than 10W30W, heavy oil viscosity's cause slow circulation through the oil passages and starve the engine's bearings for oil.

Posted on May 17, 2012

  • 56 Answers

SOURCE: I have a 1997 chevy silverado it has the vortec

check to see if you are using the right oil. for my Chey I use synthetic 5W30 all year round.

Posted on Oct 30, 2014

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Hello i have a 97 chevy with the vortec 5.7 when my truck sets overnight first start it knocks really bad and gets louder the faster i go until truck is warmed up then goes away i use a high quality oil...

Locate the sensor for the oil light. It should be on the back of the block roughly in the center, I believe. Either T into it or replace it with a mechanical oil pressure guage. This will likely tell you that your oil pressure is low, especially when cold.New pressure is 30-35 PSI. My suspicion is that you are below 20 PSI which would be normal for high mileage or abuse by a previous owner. If the pressure is down near this,20PSI, then it is time to start looking at either a rebuild or replace. You could prolong it by going to a heavier oil, either 15W40 or maybe even 20W50. They will provide extra lubrication and make the noise go away. If you live in a cold climate, I would suggest a block heater with these oils.

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Hard to say over the internet but I will try to explain. If the noise is a distict KNOCK KNOCK and it sounds like it is coming from the bottom of the engine, then it most likely is a rod or main bearing. If it is a TAP TAP noise that sounds like it's coming from the top of the engine, then most likely a valve lifer is failing/failed.
the fact that it goes away when the car is warm, makes me lean towards a bad lifter. Normaly if a bearing is bad and knocking, the noise doesn't go away.

The KNOCK noise will be somewhat hollow sounding and the TAP TAP sound will be more solid. If the KNOCK KNOCK is solid, then a rod or main bearing has most likely failed to the point that a new/reman engine will be needed.

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