top end engine noise - 04 tahoe 5.3

T

Tim W

power to teh people
Jan 23, 2011
261
103
0
39
Battle creek, MI
started up the tahoe yesterday morning to go to the store, got a nasty rythmic tapping sound coming from the top end, kinda like it was low on oil, a couple months ago I had the same problem, but at that time it had consumed 2 qts of oil, topped it back off, sound went away, never came back until yesterday

the only things I've done to the truck are switching to amsoil 5w30 a couple oil changes ago and plugs/wires, NGK platinums and regular wires

2004 tahoe 5.3flex
120k miles

any ideas? I'm gonna have the oil changed when I get back from lunch with mobil1 and a wix filter, then tonight when I get out of work, I'm gonna pull the valve covers off and see if I can see anything, if not I'm gonna pull the heads, just for grins, I'm gonna see if maybe for some reason a flexplate bolt came loose or soemthing retarded like that

maybe try switching back to a regular valvoline 5w30 or 10w30 and see if it helps, I know a lot of people dont like amsoil, maybe that's the problem???
 
Never heard bad things about amsoil.

It's possible the amsoil has loosened up some sludge, blocking a oil passageway, starving the lifters? Run some seafoam in the oil, then change right away, possibly sludge is your issue.

Do you have a vid of the tapping sound?

Flexplate came apart at the welds on my brother's 01 2500HD 6.0, where it is welded to the "hub" that bolts to the crank. Still drove ok, but made a hell of a noise, probably not long till it was going to disintegrate.
 
damnedest thing, just went home to put the battery back in it on lunch (I went full retard and left the key in it yesterday and ran the battery dead), started it up, it tapped for like 10-15 seconds, then cleared up and went away, I think its just fucking with me

yeah, I can make a vid, garrett, sounds kinda like the gm cold start knock only slightly louder, and not knowing the maintenance habits of the PO, it definitely could be an issue like that
 
You losing coolant too?

Sound like a collapsed lifter from the way you described it.
 
yeah, I've gotta dump 1/2 gallon in around every oil change, but its not visibly losing it and its not going into the crankcase

probably seeping from the water pump, but haven't had the time or money to mess with it
 
Tim W said:
yeah, I've gotta dump 1/2 gallon in around every oil change, but its not visibly losing it and its not going into the crankcase

probably seeping from the water pump, but haven't had the time or money to mess with it
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Could be weep hole on the pump, or could be the crappy castech heads if it has those.
 
If you change the oil upgrade to a 10w30 and add a half qt of Lucas oil stabilizer. I Had a pretty bad lifter tap during cold starts on my 01 and those things cleared it right up, sounds like it lasts a bit longer than just startup for you but it's worth a shot.
 
possibly, I thought the castech heads were only used through '01?


yeah, I think that the PO abused it, so the 5-30 isn't thick enough anymore

this fuckin sucks to owe this much money on it and have shit going wrong
 
Not sure on those heads, but these motors like a bit thicker oil as they get older anyways. Stick with amsoil too, its good stuff, but like stated before it probably just dislodged some sludge since you switched over at a high mileage. An upper intake clean would help too - unless something is actually damaged like a lifter.
 
Adjusted nailed it! This sounds exactly like a lifter issue. I will bet the farm you got a bad lifter in there. Audible noise from valvetrain will be present. I would tear down before the lifter goes and does a teardown for you.
 
yay, fuck me, I'm gonna change the oil tonight and run some tranny fluid through it, see if it helps

should be relatively simple once the heads are off, unless they're castech heads, then I have to shop for heads

might as well do some maintenance stuff while its apart, and talk wifey into low lift cam/springs, ls7 lifters and all new top end gaskets
 
bgray said:
Adjusted nailed it! This sounds exactly like a lifter issue. I will bet the farm you got a bad lifter in there. Audible noise from valvetrain will be present. I would tear down before the lifter goes and does a teardown for you.
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ZOMG, if only someone had suggested that sooner!

Before doing a tear down, I would first check for sludge and run a cleaner through to break up the sludge. Lot's of times sludge can break free, blocking a oil passage way causing the lifter to collapse. Besides, if the lifter "goes" it won't catastrophically destroy the engine, likely, worst case it would wear down that particular lobe on the camshaft, and he would just need to replace the cam and lifters.
 
k, we'll start there, there's only one way to find out what's going on and that's to tear into it


thanks for everyone's help, I'll update tomorrow
 
I just changed the heads out on my truck because I was running a cracked castech.

You can get by for a really long time by dumping GM Coolant tabs. Its does a pretty stellar jerb of closing in the pores in the heads. BTW - pretty easy to tell if you have a cracked head or not simply bu pulling off the valve covers. YOU WILL HAVE SLUDGE in there is coolant is seeping through the head.

PM or whatever if you want.
 
barrrf said:
I just changed the heads out on my truck because I was running a cracked castech.

You can get by for a really long time by dumping GM Coolant tabs. Its does a pretty stellar jerb of closing in the pores in the heads. BTW - pretty easy to tell if you have a cracked head or not simply bu pulling off the valve covers. YOU WILL HAVE SLUDGE in there is coolant is seeping through the head.

PM or whatever if you want.
Click to expand...

Not to mention, you can see the "Castech" markings if you pull the VC.
 
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