2005 5.3 Vortec Sounds Like A Harley

Asked by Mar 13, 2017 at 09:05 AM about the 2005 Chevrolet Suburban LT 1500 4WD

Question type: Maintenance & Repair

My 2005 5.3L sounds like a Harley! Over the past
few weeks it's developed a low throaty roar in the
bottom of the motor. Originally I had a pretty bad
tapping lifter so I put some Seafoam in the oil and
ran it for a few weeks. Just before that I also
noticed this new noise from the lower engine area.
It's gotten much worse. It gets louder/faster as the
engine revs but then subsides at highway speeds
and also when not under load, like when coasting.
Engine feels rougher now and corresponds to the
noise. The noise goes down in park, but not
completely. It also makes the noise in reverse. It's
almost like a rattle but lower. I don't think it's piston
slap because it doesn't go away and it's getting
worse.

Today I drained the oil and pulled the oil pan off
hoping to at least see something that could be the
problem. Cylinders don't look worn or gouged,
piston rods look fine, no metal bits in the oil or the
pan.

Once I got it back together, the low oil pressure
warning came on and stayed on, and the gauge
needle barely moved until I got driving. Under
constant load at 45mph or so the gauge read just
under 40, then it dives again almost to zero when
the car is stopped. I kind of wonder if this is just
the sensor being screwed up after I cleaned the
pan.

Could it be the oil pump has failed? Or, could the
knocking noise be something else like an exhaust
leak? Any advice on diagnosing from here? I really
can't even afford to have a shop look at it, but I'm
pretty confident I can do whatever I need to on my
own, I just need to know where to look.

I appreciate the guidance!

6 Answers

25,665

I would start by picking up a mechanical oil pressure gauge so you can see just what is going on with the oil pump. May also want to do an exhaust vacuum test, look for leaks and/or restrictions.

1 of 1 people found this helpful.

Thanks! I'll do that. Any advice on where to install the gauge? I'd rather not try to permanently install it through the firewall. I know there's a small protrusion above the filter on the pan, but I can't remember if it just bolts on and can be removed and drilled/tapped. Is there a better place to just tee off for the gauge?

25,665

The gauge screw into the same spot as the current sending unit, and cost around 35~50. This video may help, same concept works on any car/truck. You don't have to touch the firewall, just connect the gauge and if possible, position it so you can see it through the windshield, as it's only on there temporarily. This will let you know if you indeed have low oil pressure. Video title (How To Check Oil Pressure -EricTheCarGuy): https://www.youtube.com/watch?v=I8teB16U0LA

25,665

Just reread your question, just so we're on the same page, I meant install a temporary oil pressure gauge, not a permanent mechanical gauge for the dash.

Oh cool, just put it in place of the sending unit. I'm probably going to just fabricate my own adapter for whatever threads the sending unit has, I've got plenty of gauges I can use. Stay tuned: As soon as I have some time I'm going to get it back up on the lift while it's running and figure out exactly where the noise is coming from. Too hard to tell when I'm listening from the cab or from outside the perimeter of the car.

Well, just to wrap this up (hopefully): I took the oil pan off again today for another look and to check the oil pickup tube. I got the idea that the o-ring on the pickup tube was the culprit, so I replaced it with a new one. I was very careful to make sure it seated correctly when I reinstalled it. When I started the truck back up my oil pressure jumped up past 40 and looks perfect again. One problem down. But... When I had the pan off and I was checking the crank out hoping to see an obvious problem, I happened to notice that my flex plate is cracked in 3-4 places. It must have been turned just right to hide them all the first time I had it opened up, and they're not visible from the inspection hole on the transmission. I turned the crank a few times and saw the plate visibly rattling against itself where it's cracked, and I heard the same clunky sound I can hear when it's driving. Seems to explain everything I've experienced, so I think I've identified the problem. Even with a 2-post lift and my old man's shop, it's not a project I can get done before I have to go back to work on Monday, so I'll just limp it into a shop on Monday morning.

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