Rod Knock? Spun Bearing?

[98GMC4x4]

my truck is a 1998 GMC K1500. 5.7 vortec, automatic transmission, 4x4,

299,xxx km's, or for the Americans, 185,789 miles.

it's developed what sounds to be like a spun bearing, which i think may have been caused by the intake manifold leak(anybody that knows GM's, knows that generation has that problem, some leak internally) i think mine may have leaked coolant internally, which is not too uncommon apparently, and wrecked a rod bearing. now for my question, being the teenager i am, is it possible to pull the pan, replace all the bearings(rods, and mains), throw in a new oil pump and gaskets and drive it till I sell it? it is a strong running motor still, I just dont like that knock, its not too loud, just enough if im standing beside the motor to hear it. just another guy trying to keep his truck in the budget.

[LeoS41280]

If it spun a bearing it also has damaged the crankshaft.

[markw8]

Pull the pan to see just what is wrong. Find out how bad it is. There could be little or a lot of damadge.

 

Mark

[98GMC4x4]

i'm gonna listen a bit closer today just to eliminate the possibly of just a stuck lifter

[GMstrong]

you would know if you have a spun bearing trust me.Get vid up ill tell you.

[98GMC4x4]

i listened a bit closer with a section of garden hose today, it's definitly louder if i listen by the valve covers, than if i listen by the oil pan. but it doesnt sound like a "tick". i can hear valvetrain noise but it's nothing bad yet. is it possible my knock sensor is shot and causing it to knock? there's currently no engine light

[98GMC4x4]

also, i dont have a good enough quality camera to take a vid, the fan noise would just drown out everything else

[GMstrong]

What weight oil with that much miles you should not be running anything under 10w30.I run that and some lucas in my truck i got over 270k original motor still pulls hard.

[98GMC4x4]

right now it's 5w30. ive had it long enough for 3 oil changes

#1 - wix filter, mobil conventional oil

#2 - quaker state full synthetic

#3 - just barely did this one less than 100 kms ago, john deere oil and filter

 

would this switch from conventional to synthetic to conventional make a difference?

 

i was debating throwing some lucas in my truck soon. maybe i'll do that on monday

[Doug_Scott]

i listened a bit closer with a section of garden hose today, it's definitly louder if i listen by the valve covers, than if i listen by the oil pan. but it doesnt sound like a "tick". i can hear valvetrain noise but it's nothing bad yet. is it possible my knock sensor is shot and causing it to knock? there's currently no engine light

 

The knock sensor is used to detect detonation and adjust timing to try to get it stop. It will not cause detonation at idle.

 

A rod knock will have a "double" knock sound. Hard to describe, but on acceleration (in park I mean) you will hear a sound that is lower in frequency (sound wise) than a lifter/rocker noise, but higher pitch than a main bearing knock. A main bearing knock will typically be a "single" knock. A main knock will also have a rumble to it. A rod knock will have a "barapp" sound when you rev the engine.

 

As others have said, if you have spun a rod bearing, you will likely not be able to just slip a rod bearing in. At the very least you will need a crankshaft as well, and depending on if the bearing did indeed "spin", you may need a connecting rod (or at least having the existing one resized). To do that, you need to pull the head off. And to change the crank you will need to pull either the engine or the trans. You can change the crank with the engine in place, buy you will need to pull the trans. It is just easier to pull the engine (especially if 4wd). Get the engine checked by someone that knows what they are doing. Too big of a job to start guessing at it.

[98GMC4x4]

ill just put some lucas in it and drive it another 100,000. it's not that bad

[jro909]

watch the tests of oil stabalizers on youtube...and not the ones done by the product's company....i think you will change your mind

[Debo511]

Add two bottles of Techron fuel system cleaner to the gas tank, carboned up pistons and rings can cause a similar knocking noise. This took care of the slight knock in my 02.

[66Snaake]

Save your money - changing over to synthetic will not do any good what so ever, other than to line the pockets of Mobil/Amsoil. This model of Vortec inherently had a piston knock - tech said the piston crowns were engineered too low and the piston was not stable in the bore and "shimmyed" on every stroke - don't know if I believe that, but mine knocked from day one through today (120,000 mi). I think I would pull the valve cover, and look at the valve train, is something a little bend/misalighned?

 

My 2 cents,

 

Rick

[HawkScot]

when you changed your oil, was there antifreeze in it? Oil floats on water, so any water will be at the bottom and come out first. Pull your drain plug and take a quick sample to see if you have water/antifreeze. It needs to be setting for a while to let the water settle out before doing this. Are you losing antifreeze?