Engine issue and help

[98WhiteZ71]

98 5.7 vortec with 220K

So about a week ago truck started to make a noise. sounds like an air pump with the hood open. seems to be coming from the passenger side and towards the front of the engine. truck is still driveable with the noise but the noise is getting louder and louder each day it seems.

No check engine light
no loss in power
no loss in oil pressure

Replaced the passenger side exhaust manifold gasket and didnt fix the issue. While i had the manifold off i took a wire brush to it and could not find any cracks in the manifold

Also removed and reinstalled all the spark plugs on the passenger side head and checked the wires. Still didnt fix the issue.

Took the belt off the engine and started the engine up also and the sound was still there. So a pulley isnt causing the issue.

Also took a piece of house like a stethoscope to try and locate where the sound was coming from and couldnt find it. Tried the valve cover and nothing from there. tried the intake manifold and nothing from there.

http://vid1358.photobucket.com/albums/q776/2000_BLACK_SS/truyck 2_zpsz5z1ro12.mp4

http://vid1358.photobucket.com/albums/q776/2000_BLACK_SS/truck_zpsb6ofsjaj.mp4


at this point i am thinking that is it is something internal and if that is the case i will probably have to replace the engine or just part the truck out for what i can get from it. Just bought the truck last fall and put 10k on it and never had a problem till now. And looking around for used L31 engines they all seem to be in the 1500 range from what i could find unless i was looking in the wrong places. And seeing as i only paid 2K for the truck dont want to put another 1.5K into it.

Any thoughts on what the sound could be or what i could check?

 

[sntrym]

Just some quick things to check off the top of my head:

1. Timing plate above the harmonic balancer. Check to see that something isn't broken, cracked, or stuck on.
2. Exhaust flange gasket.
3. Cracked manifold. Pull it and have it magnafluxed by an engine shop. Cracks don't always show up to the naked eye.

 

[Ironhead]

I'm thinking exhaust as well. Have you tried (carefully!) putting your hand down around the exhaust manifold, and at the joints in the pipes to see if you can feel the puffs of exhaust? Do this with the engine idling.

You didn't mention, but I assume the engine idles well, pulls properly at higher revs, and has normal oil pressure and coolant temp. If so, it's still possible that it's an internal mechanical problem, but I don't think it's likely.

 

[superdave]

For exhaust leaks, tear off a little piece of a paper towel and use a pair of needle nose pliers to hold it and move it around the manifold and pipes. It will show where the leak is as it starts flapping around.

 

[98WhiteZ71]

again it is not an exhaust leak. trust me on this I have take the manifold off and replaced both the manifold gasket and doughnut gasket. also scrubbed down the manifold with a wire brush and there is no crack in the manifold.

Im going to take the valve cover off the passenger side this weekend and see if a rocker or a spring has failed and if that isn't it I will be
taking the alternator and water pump off and check so see if the harmonic balancer failed and is hitting the timing cover. hopping it is one of these two as it doesn't seem to be bottom end noise.

 

[kennythewelder]

The muffler shop I use, uses a rubber hose about 4 feet long to listen for exhaust leaks, but if you are 100 % sure it is not exhaust, then the next step is to use something to listen with. A mechanics stethoscope is perfect for this. Jsgs has one for about $10 It is hard to tell from a video, just what it is. It does sound like an exhaust leak, but it could be a lot of other things too. Being it goes away when you rev the engine, it may be a lifter issue. lower oil pressure at idle, a week or clogged up lifter, would click, then when the engine RPMs go up, the oil pressure goes up and the lifter gets enough oil to start working. This will be hard to see without the valve cover on, and if you try to start the engine without the valve cover, you will have oil everywhere. With a mechanics stethoscope you can touch the end in different places on the engine, and trace the sound to where it is loudest. This will get you close to where the problem is.

 

[98WhiteZ71]

The muffler shop I use, uses a rubber hose about 4 feet long to listen for exhaust leaks, but if you are 100 % sure it is not exhaust, then the next step is to use something to listen with. A mechanics stethoscope is perfect for this. Jsgs has one for about $10 It is hard to tell from a video, just what it is. It does sound like an exhaust leak, but it could be a lot of other things too. Being it goes away when you rev the engine, it may be a lifter issue. lower oil pressure at idle, a week or clogged up lifter, would click, then when the engine RPMs go up, the oil pressure goes up and the lifter gets enough oil to start working. This will be hard to see without the valve cover on, and if you try to start the engine without the valve cover, you will have oil everywhere. With a mechanics stethoscope you can touch the end in different places on the engine, and trace the sound to where it is loudest. This will get you close to where the problem is.

Also took a piece of house like a stethoscope to try and locate where the sound was coming from and couldnt find it. Tried the valve cover and nothing from there. tried the intake manifold and nothing from there.

Yep tried that already and couldn't find anything. that is why I am leaning towards the harmonic balancer as its on the outside of the engine and really wouldn't be able to pinpoint it with the stethoscope trick.

 

[superdave]

A cracked flex plate can make a lot of noise too. I know you said the front, but sounds are hard to pin down.

 

[GL1500]

Just an observation. i counted the noises in the first video up until you revved the engine and came up with approx. 330-350/min. Assuming your idle speed is ~650 rpms this tells me it's occurring every other revolution. This would seem to rule out lower end issues including the harmonic balancer. Possibly a valve train or timing chain issue but I'm leaning toward vacuum leak. This would also explain why the noise lessens when you rev it. I know you listened with a hose but I would try spraying carb cleaner around the edges of your intake, vacuum lines etc. As I'm sure you know change in rpms indicates a problem.

Best wishes,
Steve

 

[98WhiteZ71]

So took the fan clutch and fan off and found at least the next area i will be looking

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Im thinking if i take the alternator, alternator bracket, pulley tensioner, water pump off i should be able to get a much better look at where this is coming from. So that may happen tomorrow or slowly during the week. For now its time to head to the bar for some beers and blackhawks game