: ticking tapping noise in engine video attached

07-22-11, 09:59 PM
hello all, i did some searching and found some info but i decided to make a video of the noise and hope that someone could point me in the right direction. i have had the low oil message flicker on and off and even comes on after an oil change.
This noise was just noticed today it got pretty loud as the car warmed up, i waited about 2 hours and went out side to crank it up and it wasnt as noticeable but after it warmed it got louder, and as i accelerate the sound has a faster rhythm.

history 2001 deville
car has 90k miles
oil is changed regularly.

ok here is the video

07-22-11, 11:53 PM
Sounds like a rod knock to me. Could be piston slap, sounds more bottom end to me.......Is the oil pressure light on? Or flashing?

07-23-11, 12:34 AM
yes oil pressure warning message is on, idle is normal other than the noise

07-23-11, 12:36 AM
Just read your original message again. "Low oil message flicker on and off evan after an oil change".

I suggest replacing the sensor for the oil level.

Yet for the noise that I heard, you're doing some bottom end work.....

07-23-11, 12:37 AM
I bet it's a little quieter when the car has sat overnite then started. As the vehicle warms up, the noise gets worse, I pressume.....

07-23-11, 12:50 AM
yes i went out to start it just a moment ago, with the initial start you can hear the noise but then it quites down, but apon acceleration it;s still there

07-23-11, 12:59 AM
Unfortunately, my friend you have a knocking rod bearing.

On start up, it's probably faint, but once the oil warms up and "thins" out the clearance between the bearing and the crankshaft journal gets "larger". Making the noise more pronounced.

Upon acceleration/ opening the throttle, you speed up the rotating assembly (crankshaft, pistons, connection rods etc), the bearing clearance is now "too big/excessive" making that rod bounce/knock on that particular journal.

I suggest you start looking for another motor or saving your money to repair that one.......

07-23-11, 01:00 AM
90k is a shame for that motor to be knocking. That motor must have had a rough life......

07-23-11, 09:02 AM
thanks all!
, not what i wanted.to .hear,
but it is what it is,
& i appreciate your quick responses
now if i were to attempt this job myself would i expect to pull the entire engine and how long would this fix take?

07-23-11, 10:20 AM
The entire drivetrain comes out the bottom of the car, the engine removed and placed on a stand, inverted, and a complicated disassembly begins: The Northstar block is actually in 3 pieces: the cylinder block, to the main bearing center line; the halfcase, and the oil pan - all bolted together to form a single rigid structure. The halfcase is also the main bearing lower halves as well as a bolt girdle. There is an oil distribution manifold (which must be replaced) attached to the halfcase underside.

This overhaul is not for the faint of heart - if the crank journal(s) is/are scored, the crank cannot be machined: it must be replaced.

You will NEED a real GM Service Manual, by Helm, from either eBay or www.helminc.com

This is just a taste of what you're up against:

(Notice that there are no gaskets on the halfcase seal surfaces: the seals are formed silicone beads set into machined grooves in the block and oil pan.)

07-23-11, 11:10 AM
To get an idea of what you're up against, look at this:


07-23-11, 11:39 AM
Sub, told you the truth pertaining to what has to take place.

I have removed a Northstar through the top of the car without dropping the cradle. Not exactly the preffered method of removal, but I'm not comfortable loosening all those other components and THEN separating the engine and trans for repair. Sub and this forum have always given sound advice.

I've worked on plenty of motors and this one is truly finicky. All aluminum, throw away crankshafts if not in tolerance?! What happened to machining the crankshaft?! I guess not for the northstar.

Yet, somebody must be machining cranks because I see crankshaft kits for the engine. I guess they don't know that they're not supposed to be machined......

The half case seals aren't even used anymore. You have to get this new sealant from GM to even reseal that area of the motor. 88861417 squeeze tube or 12378521 cartridge.

This repair is not for someone ready to do battle.

You can't show up at this gun fight with a water pistol.......

07-23-11, 12:29 PM
Yet, somebody must be machining cranks because I see crankshaft kits for the engine. I guess they don't know that they're not supposed to be machined......

There is a specific, direct guidance on this in the GM service manuals. I believe it has something to do with the bearing journal rolled fillet radius edges. (EDIT) Machining compromises the fillets, thus weakening the crank.

07-23-11, 12:48 PM
Thanks Sub,

I'm beginning to wonder how many of those crankshafts kits have been sold without issues or if they actually been having problems with them.

Either way, this is way too involved to take a chance finding out.....

07-23-11, 12:58 PM
To make the crank less subject to fatigue cracks a cold rolling process is used in the bearing fillets. If the fillets are damaged or modified in any way this rolling process must be repeated. The highly specialized tooling used for this process is only available at the factory. Anybody selling reground cranks is depending on margins of safety that don't exist.