LS4 clattering

rjayl said:

I would start with the oil pressure. What is it? Is the clattering only at start up?

Typically when the AFM has issues the engine miss-fire code will be detected when going back into 8cyl mode.

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That's next for me to do. I have collected some plumbing parts to allow connecting an oil pressure gauge along with the stock sending unit. If that doesn't work, I will just swap the gauge for the sending unit.

After startup, the clattering mostly subsides, but there is some residual ticking that continues.

I don't have any codes, but the battery had run down, so anything stored has been cleared.

I'll post some readings later, but it may be the weekend before I get to it.

Thanks for your reply.


Doug

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plano-doug said:

That's next for me to do. I have collected some plumbing parts to allow connecting an oil pressure gauge along with the stock sending unit. If that doesn't work, I will just swap the gauge for the sending unit.

After startup, the clattering mostly subsides, but there is some residual ticking that continues.

I don't have any codes, but the battery had run down, so anything stored has been cleared.

I'll post some readings later, but it may be the weekend before I get to it.

Thanks for your reply.


Doug

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If you haven't done it already change the lifter filter under the oil pressure sensor. Generally it clears up lifter clatter on the AFM 5.3L in the trucks and the AFM LS4 FWD engines in our cars.
BTW I use the AC Delco UPF48R engine oil filter that GM specs for the LS7 on my LS4. It filters out smaller particles than the stock filter and with AFM every little bit helps.

I'd do a cylinder leak down test if the AFM filter and an oil change doesn't clear up the noise.
If the leak down doesn't point toward piston ring blowby and you don't have rod/main bearing issues then I wouldn't bother with going any deeper than a new oil-pump/pickup screen and maybe the cam/lifters.

Look in the service manual. If the LS4 uses torque-to-yield, "stretch", head bolts change them out with ARP head studs. I had some real bad experiences with TTY head bolts on 1.6L VW diesels and 350DX Oldsmobile diesels. ARP studs fixed head gasket issues on both of em permanently.

As I said in my PM I'd get one of the two-bolt oil pump pickup tube girdles so the pickup tube doesn't get cocked to one side again and I'd shim the oil pump and drive gear even tho @ 50% of the internet experts and GM dealership techs say you don't need to. If it's done and doesn't need to be you don't loose a thing.

Swap out the LS4 timing chain tensioner to the LS2/LS3 damper.
The camshaft retainer plate has a cast-in seal to cover the lifter oil galleries. This seal doesn't like being disturbed. Just replace the plate/seal. Some LS engines use countersunk head bolts on this plate and some use flat bolts. Whatever type your new plate takes you'll only need one because the Trick Flow damper bracket covers and uses the other three.

Timing chain and sprockets are up to you. GM sells them as three separate pieces. :WTF: A timing chain set is one of those wear items I typically don't leave out once I'm down to em unless they are pristine.

The AFM lifter guides are different from the non AFM lifter guides so they should come in the AFM delete kit. The guides are retained by the cylinder heads on the LS motor so the heads have to come off to service the camshaft and lifters.

Really if you've done a head gasket job on a V8 or V6 Toyota, BMW, Nissan, Buick, Caddy, Pontiac, Oldsmobile, Lincoln, Ford, Mopar, Holden, or Chevy you can do the lifter swap on an LS engine. Really nothing that oogie boogie about a head gasket job. Just tedious work. Much easier on a transverse V6/V8 engine with it mounted on an engine stand.

The camshaft isn't any more involved than an old fashioned V6/V8 either except that there's no easy in-frame way to pull the cam out in a transverse engine bay. The Transverse engine will need to be tilted up, if that's possible, or removed from the engine bay to slide the cam out.

hatzie said:

<snip great post!>

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Thanks for your detailed reply, Hatzie. Good stuff!

I replaced the screen a while back. And my low oil pressure light went away. So I'm satisfied I'm getting some lubrication up top. A check later this week with a gauge will tell me more.

As for pulling a head, as close as I've come to that was taking the (flat) head off an old Briggs&Stratton many years ago. Seriously, I need to add that to my resume. Up to now, I've pulled valve covers, done a timing chain, dropped a few transmissions, done a few lower intake gasket sets, and swapped a couple oil pans. But I still haven't pulled heads or torn into a short block.

I subscribe to the Mechanocratic Oath: Don't screw something up while you're fixing something else That is, if I'm venturing into new territory, I like to have, at the very least, a memory of watching someone else do it. Even then, I'll thoroughly read up on it and, courtesy of modern technology, watch a couple YouTube videos

UPDATE>> I just fired it up and took it for a drive. It's pulling pretty good, but I can hear and feel a misfire. After the clatter at start-up subsides, I had some sustained ticking, but eventually that went away.

For a while, the ticking would fade or go away completely after I revved the motor a few hundred RPMs. But after letting it idle back down, the ticking would come back. But eventually it was all but gone.

As for the misfire, the scanner says P0300 and P0304. Cylinder 4 is one of the AFM cylinders, so that's where I need to focus, I suppose.

This weekend, I hope to pull the plug and swap the coil pack to see if that makes any difference. And I'll try to do the leak down test as well.

Thanks again for your comprehensive reply!

Doug

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Mine has a similar problem. Back In the winter when It was -20 It had no oil pressure at Idle when the engine was first started, you had to raise the Idle for a few minutes and then It would hold pressure. But now that's It warm around 50 degrees when cold starting It Immediately jumps to 50 psi. The colder the temp Is the lower the pressure. Everyone pointed to the oil pickup tube o ring. I was gonna have It replaced but the shop that I go to said they had just did a Silverado and that didn't fix It and It turned out to be the camshaft bearings which Is also common on LS's. But every engine Is different and I just don't believe that's the problem with mine. As mine Is silent when running, just the common lifter tap on startup that goes away after a second. It switches from 4 to 8 cylinder with no problems. Mine also gives a misfire for cylinder 5 when I beat on It and that's not a AFM cylinder. I believe It's the coil pack going out, I need to swap It around and see. But I sat In It and let It Idle and I could hear It stumbling but no misfires on the counter and the Idle was dipping down to 500 at times and the ac was not on. Although awhile back It did throw a crank sensor code but It hasn't come back so maybe that's going out too. Mine just hit 155k.