LS1 cold start noise/chirp sound
11-13-2017, 10:38 AM
#1
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LS1 cold start noise/chirp sound Hello, I have recently acquired a 98 Z28. I should start off by stating I am new to owning an LS car but not new to working on them. I'm a tech at an import dealer so I have a decent amount of repair/diag skills. Since it has gotten cold out I've noticed a strange chirping noise on cold starts. It quiets down when its warm but you can still hear it when the hood is popped and you're standing in front of it. Not sure if its headers leaking or if the previous owner messed something up when he installed the cam, such as not setting pre load or something isn't lined up right. I pulled the belt and started it and the noise did not go away. Not sure if it's lifter noise, piston slap, exhaust leak, rocker noise. I can't determine what It is. It doesn't help that a "Cletus" owned it before me, so there is no telling what was done and not done or what wasn't done properly. Does anyone have experience with this noise that can help in any way? Thank you. the link to the video is posted below.
Last edited by Chris Bauer; 11-13-2017 at 02:45 PM.
11-13-2017, 12:15 PM
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Update, I've checked all the header bolts and they're tight. Doesn't rule out a failed gasket though. I stuck a stethoscope on the motor at idle and the noise is the loudest on the intake manifold. Mostly humps #2 and #3.
11-13-2017, 02:44 PM
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11-13-2017, 02:58 PM
#5
Piston slap doesn't chirp. It knocks. I've owned piston slap LS motors for 10 years and been around several built motors with short skirted pistons with high clearances that slapped. Piston slap sounds like knock or like a diesel kind of sound.
That sounds like valve train to me. I'd pull and inspect all the rockers and push rods (while they are out roll them on a flat surface to make sure they are straight) to start with. Especially the rocker trunions and bearings. May even be a funny lifter roller also.
Sounds kinda like a bearing squak. Which bearing hard to say but maybe even a lifter roller.
Pull the drain plug and look for shavings on the drain plug. Drain the oil into a clean drain pan and inspect for shavings or metallic in the oil. Cut open the filter and have a look there also.
That sounds like valve train to me. I'd pull and inspect all the rockers and push rods (while they are out roll them on a flat surface to make sure they are straight) to start with. Especially the rocker trunions and bearings. May even be a funny lifter roller also.
Sounds kinda like a bearing squak. Which bearing hard to say but maybe even a lifter roller.
Pull the drain plug and look for shavings on the drain plug. Drain the oil into a clean drain pan and inspect for shavings or metallic in the oil. Cut open the filter and have a look there also.
Last edited by 00pooterSS; 11-13-2017 at 03:04 PM.
11-13-2017, 03:11 PM
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Piston slap doesn't chirp. It knocks. I've owned piston slap LS motors for 10 years and been around several built motors with short skirted pistons with high clearances that slapped. Piston slap sounds like knock or like a diesel kind of sound.
That sounds like valve train to me. I'd pull and inspect all the rockers and push rods (while they are out roll them on a flat surface to make sure they are straight) to start with. Especially the rocker trunions and bearings. May even be a funny lifter roller also.
Sounds kinda like a bearing squak. Which bearing hard to say but maybe even a lifter roller.
Pull the drain plug and look for shavings on the drain plug. Drain the oil into a clean drain pan and inspect for shavings or metallic in the oil. Cut open the filter and have a look there also
That sounds like valve train to me. I'd pull and inspect all the rockers and push rods (while they are out roll them on a flat surface to make sure they are straight) to start with. Especially the rocker trunions and bearings. May even be a funny lifter roller also.
Sounds kinda like a bearing squak. Which bearing hard to say but maybe even a lifter roller.
Pull the drain plug and look for shavings on the drain plug. Drain the oil into a clean drain pan and inspect for shavings or metallic in the oil. Cut open the filter and have a look there also
11-13-2017, 03:46 PM
#7
this is what I was thinking as well. I was gonna check the rockers and push rods and the pre load this weekend. I drained the oil and caught it. It was metallic but not magnetic. Looked like aluminum more than anything. I'm wondering if the lifters dropped when the previous owner did the cams too. The noise almost completely disappears when it's warmed up. But when its cold it changes with the revs.
Inspect the rocker arm bearings (trunions) very carefully, they are known for coming apart and spitting out the roller bearings. If it has upgraded roller trunions in the rocker arms those are known for wearing out in short mileage.
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11-13-2017, 04:04 PM
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I honestly believe it's in the valve train. But i don't think it's the lifters. (Im probably wrong, like i said im new to owning one of these) They sound more like a sewing machine to me. This sounds like a bird stuck in the intake. Can't hear anything abnormal in the heads or the headers or the block. I really only hear it in the intake itself. Changes with revs but almost disappears when it's warm. I want to believe it's a pushrod or a bad rocker or even a bad pivot ball.
11-13-2017, 04:07 PM
#9
I honestly believe it's in the valve train. But i don't think it's the lifters. (Im probably wrong, like i said im new to owning one of these) They sound more like a sewing machine to me. This sounds like a bird stuck in the intake. Can't hear anything abnormal in the heads or the headers or the block. I really only hear it in the intake itself. Changes with revs but almost disappears when it's warm. I want to believe it's a pushrod or a bad rocker or even a bad pivot ball.
11-13-2017, 06:11 PM
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11-13-2017, 06:59 PM
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Im just thinking, I wonder if the oil pump could be making that noise, I always use feeler gauge to space pump away from crank, if you don't crank could rub on pump housing.
I have never read anybody having that problem, just thinking with my fingertips.
I have never read anybody having that problem, just thinking with my fingertips.
11-13-2017, 07:04 PM
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that's s good point but as far as I know the only thing replaced was the heads out. It's a GM dealer replaced shortblock at 30k as far as I know. I dont know why the pump would be out of spec.
11-13-2017, 07:15 PM
#16
Not necessarily out of spec. just close on one side. And its not the crank that could rub, I
was wrong, its the pump drive gear that mounts on the crank that can rub the pump housing, I had to go look. Well anyway, you will find it eventually, Good Luck
was wrong, its the pump drive gear that mounts on the crank that can rub the pump housing, I had to go look. Well anyway, you will find it eventually, Good Luck
11-14-2017, 11:37 AM
#19
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Was also thinking on this a bit more and would a lifter issue stop after warm up? I would think a valve train issue would make noise no matter if warmed up or not. Just throwing that out but some others that have dealt with lifter issues could chime in.