Question about 2003 GMC Sierra

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I have a 2003 gmc Sierra half ton 4.8 liter that has a knock that sounds like lifters

The noise sounds like lifters it is always there when it is running . Oil pressure is good. Is there anything else it could be or anyway to check or trouble shoot what it could be. I want to do the lifters soon I just want to make sure I'm not wasting my time

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There is,If you do the lifter you could be after something else,The noise sounds like a collapsed lifter,A collapse lifter can cause a misfire,The 2003 GMC sierra or I should say the 4.8 engines suffer from a cut O-ring between the oil pump screen and the oil pump causing oil areation,resulting in lifter noise,The noise will be present a cold start and then diminish at warm up.I have a 2003 gmc Sierra half ton 4.8 liter that h - 12_3_2012_8_08_44_am.gif

Posted on Dec 03, 2012


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SOURCE: 1990 GMC Sierra lifters knocking. Oil pressure

I doubt it....It could be a totally worn out engine.

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SOURCE: 2004 gmc sierra truck hydraulic lifter problem

Plugged oil gallery in the head

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SOURCE: 2003 GMC Sierra Knock sensor and oil pressure??

the knock sensors are located below the intake plenum,or,upper intake manifold as some call it, they screw into the lower intake, the front one is sensor 1, the rear is sensor 2. it is wise to change both if you have some miles.since you are going to be buying a gasket set to do this job.the sensors are cheaper than the gaskets.

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SOURCE: I have a 2003 gmc


Posted on Oct 20, 2010

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SOURCE: 07 GMC sierra 111,000 miles

When you replace spark plug look at the gap is it worn(just compare it to a new on)now is this noise at idle or are you acclerating at idle its a lifter noise.If its at acceleration then time for spark plugs fuel filter.Remeber to use the proper weight on it.Dont listen to someone that says you can use a thicker oil. Make sure the oil you use has not been strip of zinc which API has removed and allot of premature engine failure are occuring. Use mobil stay away from penzoil they have no anti wear additives engine are wearing out quickly.

Posted on Apr 21, 2011

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Moter knocks when i first start it then goes away

I had a chevy 2002 avalanche,2004 chevy tahoe both after 20,000 miles developed a mild lifter or slight bearing knock.When I confronted chevy with this problem they stated this was normal for the 5.3 liter v8.Being a mechanic myself didnt think this sounded right.My friend has a 2003 gmc yukon and motor sounded same way.I no longer own my chevy,But my friend still has yukon with 150,000 plus miles and yet it still knocks when you start it.this is just a problem with chevys and other gm products.

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My wife ran the jeep rly low on oil i had to put in 3 and half liter i put 3 of penzoil and half of lucas to help the knocking ...well the knocking is almost gone but the jeep wont pick up like its not...

If it's knocking, chances are that either some of the lifters collapsed or you damaged a crank bearing.
Lucas is a great product but no additive can fix a mechanical problem like that. Lifters will give you a noise from the valve comers. Bearings give a more solid knock from deep inside the engine. Sometimes a collapsed lifter will free itself up if left at idle if you use marvel oil to dissolve gunk inside, but with a low oil condition as the cause, it's possible that the lifters or cam itself was damaged...that I can't tell you because I can't see inside from here.(you'd need to remove and inspect them)
Lifters not functioning will not allow the valves to open all the way which can cause a performance loss but a bearing about to spin can overlap and cause it to drag. Usually that won't happen for very long before the engine locks up entirely.
Sorry I can't give you a "turn this screw and it will be better" type answer but it is what it is.
Best advice is to have an experienced tech evaluate it so you know where you stand.

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I have a 1998 GMC Sierra, when I start it in the morning it makes a knocking noise but once it warms up it goes away, what could be causing this?

We really need to know more about what kind of knocking you are hearing.

Pinging, clink clink, sounds like the time you got bad gas and put a strain on the engine causing it to knock. Airflow sensor telling the injectors how rich or lean to mix the fuel. Computer sets fuel air mix. timing , ect to match operating temp and if it is going bad throws the whole thing out of balance.

Ticking... click click click sound from the top of the engine that gradually fades,,( lifters on cam and valve chatter) sticking lifters can be treated with oil additive to clean them out if they aren't stopped up to bad. If that doesn't work or the noise keeps getting louder you need to have someone look at it or you can damage your cam or bend a valve and that can lead to a cascade failure of cam. lifters, valves and possible broken pistons.

Knocking. KNOCK KNOCK knock knock,from the bottom of the engine that fades ( rod bearing worn and slapping the crank til it gets enough oil to float it on the crankshaft or crank bearings worn and bearings trying to spin in the races)
If it is a hard knock could be a worn rod bearing or a partially stopped up oil port in the crankshaft that doesn't let the oil do its thing until it is warmed up. This problem can be slowed down with cleaning additives but the damage has already been done and will do nothing but get worse over time. If it is a bottom end bearing don't let it totally fail. If you have a mechanic you trust get him to listen to it and help you figure out what needs to be done. Once you have heard these noises and have someone point out the differences you don't forget them.
Remember. Sooner you get this figured out the less damage done and the cheaper the repair bill will be.

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1990 GMC Sierra lifters knocking. Oil pressure

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You have a coolant leak into the lifter valley,I suspect the engine is equipped with aluminium cylinder heads,cracks can appear at the cyl.head bolt bosses causing a wash out condition to the lifters.Add a coolant dye,run engine for 15min,apply a pressure test to cooling system,remove left valve cover & rocker rail & check around centre 4 cylinder head bolts for signs of the dye.The only correction is replacing the cylinder head & while you are at it also have Tec check the right side as well.

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