ls1 Tapping noise we cannot get to the bottom of. Please help

ferrari360man · 10-04-2009, 10:23 AM

So we bought a 1997 vette from a guy named rick clarke on the corvette forum. This tool sold us a car for 12 grand and promised a properly running motor and that was exactly what we did not get. Well months later, after he sent us parts to replace inside the motor, it is still not right.

When we got the car in may we noticed it had unusually low oil pressure and there was a tapping sound. So the next day we had the oil changed which improved the low oil pressure a little. What we found next in the oil was even more unusual. A piece of what appeared to be a dowel pin or something of the sort. It was a pin the same exact size in diameter as the pin in the camshaft sprocket under the front cover. So, we pull EVERYTHING APART! We removed the heads, and the entire front cover etc. We found nothing unusual. No broken valve springs, no broken retainers, all the rockers and their needle bearings were in tact, and the pin for the camshaft sprocket was also there and in one piece. The camshaft had no unusual scoring on it, and appeared to be well. So, now we were thinking its lifter failure maybe. So we buy all brand new lifters and pushrods from gm, all new head gaskets and bolts. We put the entire motor back togethor, and it runs, and still has this tapping sound.

The tapping sound is still coming from the same place on the left side of the motor. It seems to match the rpms as you hit the gas. The oil pressure is still pretty low. When cold its around 22 psi, and when hot, it can fall as low as 5-8psi. It will NOT go above 40 psi under WOT. This motor does have about 90k miles on it. There was no physical damage to the pistons, and I do not know where else to look.

We noticed no shards of metal in the oil, and no silverish looking tint to the oil indicated bearings are going out, and the worst part is even though the motor taps... it runs wonderfully. Doesnt skip a beat, doesnt smoke, and it idles fine.

Im stumped. We were thinking to replace the oil pump, but still cant say if that oil pump would be the source of the tap.

davidws6 · 10-04-2009, 10:52 AM

With oil pressure that low, almost has to be the bearing clearances are too wide. Usually when a pump fails, it goes all together but anything is possible.

Does it sound like valve train clatter or possibly piston slap ? Piston slap should change with the operating temperature of the engine.

Any way you can record a sound clip or a Video ?

KRAZY K 2000 TA · 10-04-2009, 11:46 AM

worn rod and main bearings,maybe cam bearings.

ferrari360man · 10-04-2009, 11:57 AM

http://www.youtube.com/watch?v=Dde7gzfpbhM

http://www.youtube.com/watch?v=EWgekjQTNs0

there is some whirring noise also at under 2k rpms when its warm

KRAZY K 2000 TA · 10-04-2009, 12:21 PM

whirring noise sounds like the torque converter the other noise weird?

ferrari360man · 10-04-2009, 12:33 PM

um this is a manual shift car. Torque converter? I think it needs a new bottom end

KRAZY K 2000 TA · 10-04-2009, 02:33 PM

did not know it had a standard sorry?had a bad converter in my turbo 400 when i got it and it whirred bad is all

davidws6 · 10-04-2009, 02:47 PM

That whine sounds like a vacuum leak. Cause on that last decel it sure picked up in volume.

As for that noise, sounds to me like a Rod bearing has too much clearance !

It sounds too,,,, heavy or deep (metallic) for a valve train noise.

In fact sounds almost like my 01 TA when I bought it. It had a rod bearing that had gone south....

ferrari360man · 10-04-2009, 02:54 PM

that sucks! ohwell, I need a motor.

$750 L98 · 10-04-2009, 02:57 PM

That's definitely some bad rotating assembly noise. I have a bit of piston slap/lifter tap when mine is cold, it sounds nothing like that. What you have really sounds like maybe a minor bent rod, or a rod/piston bouncing around.

ferrari360man · 10-04-2009, 04:17 PM

that would make sense, there are some eyelashes on the tops of the pistons I noticed when I had the heads off.

99RTA · 10-04-2009, 07:01 PM

Interesting noise, i don't think its a bearing or lifters....sounds like something hitting something. try this......pull each fuel injector plug off one at a time as its running. See if the noise changes or goes away. I'm betting it doesn't. I would pull the starter off and look at the flywheel convertor bolts.

Also post up some pictures of the part you found laying inside. AND a video of you revving the engine from a idle quick up to like 3k. If its a bearing it will knock harder as it revs.

ferrari360man · 10-04-2009, 07:10 PM

I pulled each spark plug wire and no change was heard.

flyin'duc · 10-05-2009, 12:27 PM

I have a 02 TA Ls1 making almost the exact same noise, any ideas? I dont think it is a rod or main, they are usually much deeper and get worse quick, we thought it might be in the clutch as it popped just as it was fixing to start, so we pulled the trans and clutch out and ran the engine it did change slightly but not much? any help would be appreciated

themonkeyman89 · 10-05-2009, 12:54 PM

Why didn't you take a look at the bearings when you had the entire motor apart?

ferrari360man · 10-05-2009, 01:09 PM

entire motor meaning top and front. Not bottom. I have no idea the condition of the bottom. At this point, im throwing in the towel and looking for a replacement. The only thins left I did not check, was the rod bearings etc, and if it is that, im not paying for a rebuild, so were in the market for a used one.

themonkeyman89 · 10-06-2009, 10:21 AM

Quote:

Originally Posted by ferrari360man

entire motor meaning top and front. Not bottom. I have no idea the condition of the bottom. At this point, im throwing in the towel and looking for a replacement. The only thins left I did not check, was the rod bearings etc, and if it is that, im not paying for a rebuild, so were in the market for a used one.

Oh ok, my bad. Yeah, sounds like a replacement is the best bet. Building your block might not be a bad idea though...

ferrari360man · 10-06-2009, 10:36 AM

well, Ive never built a block before, so what I think ill do is rebuild this block slowly on my own when I put a used one in here. I am going to need a motor for my z06 when I blow it up with the charger eventually. UNless im lucky of course and that doesnt happen.

99RTA · 10-06-2009, 10:47 AM

You don't even know what the noise is....i can tell you from here its NOT a bearing. I'm betting something in the trans area or flywheel etc. You think replacing this or that will solves this???

Suppose its in the trans and you put another engine in and it does the same thing............................

Dig into it and diagnose the noise.

ferrari360man · 10-06-2009, 03:19 PM

its not a transmission failure. This motor also has severely low oil pressure. I am more than sure the tap and low oil pressure is related. Which excludes the tranny as a possibility.