: Loud Valve Tapping 2002 Sts



fuldun
11-30-04, 01:30 AM
Anyone experiencing this problem? When I first start my 2002 STS the valves tap very loudly. Car has 53,000 miles. Any chance of GM covering this repair since the car is just out of warranty?
Mark

growe3
11-30-04, 02:11 AM
If you have the correct amount and viscosity of oil, you may have carbon rap. Excess carbon can cause knocking, more noticeable when cold.

WOTs are recommended to keep the rings freed up and the combustion chambers from building up excess carbon; a known fact on the Northstar engine.

Normally a good safe place is the on ramp to the freeway. Floor it from about 35 MPH and let it shift when it wants to (about 6500 RPM). Get to at least 70 MPH. Be ready for the torque steer to pull the steering wheel, easy to control but if you are not used to it, it can be surprising. Donít worry about over revving the engine; the computer will control the transmission shifting within safe limits.

Glance in your rear view when safe as you are doing this. If you see dust or clouds of smoke you are way overdue to exercise this engine. A properly exercised engine (daily) will not produce any smoke or dust, and will tend to use less oil.

When exiting from the freeway or slowing down from a grade, shift the transmission into 3rd. Again this will tend to flutter the rings and keep them working freely.

These little exercises are fun and keep the engine working as designed. No offense, but as they say, "this is not your fathers car"; this is really a race engine dropped into a Cadillac.

Just be sensible where you open it up.

-George

RKunz2
11-30-04, 01:16 PM
George,

Old discussion, but just came across it.

I have a 2000 STS that does the same thing. It's not carbon, already alleviated that possibility. Several trips to the dealer yielded no results either. I'm convinced it's something in the valve train, or possibliy worse, the lower end. Generally, if it's carbon build-up, it will do it most on cold start-ups. Mine does it at full running temp. I run Mobil-1 5w-30 in So. Calif. climate and have since I purchased the car with 22,609 on it in 2002.

Both the dealer and I clean the throttle body regularly and I have no signs of smoke. I "stretch" the engine frequently enough anyway, so I have little doubt about my rings running freely. It's a fun car to put to work when the opportunity presents itself.

That's my 2-cents. :hmm:

Anthony Cipriano
11-30-04, 02:33 PM
George,

Old discussion, but just came across it.

I have a 2000 STS that does the same thing. It's not carbon, already alleviated that possibility. Several trips to the dealer yielded no results either. I'm convinced it's something in the valve train, or possibliy worse, the lower end. Generally, if it's carbon build-up, it will do it most on cold start-ups. Mine does it at full running temp. I run Mobil-1 5w-30 in So. Calif. climate and have since I purchased the car with 22,609 on it in 2002.

Both the dealer and I clean the throttle body regularly and I have no signs of smoke. I "stretch" the engine frequently enough anyway, so I have little doubt about my rings running freely. It's a fun car to put to work when the opportunity presents itself.

That's my 2-cents. :hmm:

Lower end noises don't usually "tap" on startup. Given the history of the lower end performance with the Northstar I wouldn't suspect the lower end. Can you describe better how the noise sounds and when it comes and goes?

The Northstar has full floating wrist pins in the pistons due to the rev range of the engine and the specific power output. Full floating pins will commonly "tap" lightly on start up as the residual oil film is pounded out in the first few firing events and then the pins will make the tapping noise for several seconds before the oil is replenished. This can happen hot or cold but usually after a longer soak. Characteristically you would hear the engine start and it would be quiet for 5 to 10 seconds - then you'll hear the tap-tap-tap (a fairly light tap just like a lifter) of the pins for 15-20 seconds and then it'll disappear. This is just a fact of life with full floating pins and one reason that manufacturers tend to shy away from full floating pins in OEM applications. High performance engines with full floating pins exibit the noise but no one notices due to other distractions (open headers, for example). The Northstar combats this by holding the piston pin clearances to a bare minimum. The pins are almost a press fit but are really full floating - but in the case of a limit stack ie. small diameter pin and large diameter piston/rod bushing - the noise could be evident. If this is the noise you're hearing then rest easy. It's the sound of performance. The more clearance in the floating pins the better - so the "noisy ones" are the best ones but the tighter ones are quieter.

Otherwise, upper end or valve train noises are pretty rare. It may be a piece of debris in a stationary hydraulic lash adjuster (SHLA) or a defective SHLA that has a problem with the surface finish of the check ball in the SHLA. The SHLA contains all the conventional parts of a hydraulic lifter but it the stationary pivot point for the roller rocker arm in the 2000 and later Northstar engines. If it's that you should be able to pinpoint the noisy SHLA with the cam cover off and by listening with a piece of hose like a stethscope.

I would really flog the engine hard to make sure it's not carbon build up, though. There are cases where excessive carbon build up can be difficult to remove and cause the startup clatter or cold carbon rap even with the engine somewhat warmed up. The way the noise comes and goes is really the give-away. The carbon rap goes away with piston temperature where a valve train noise will usually disappear with oil pressure popping up. The valve train noise or piston pin noise will disappear suddenly as oil gets to the correct area but the carbon rap will disappear slowly as the piston warms up.

You can also try disconnecting the spark to individual cylinders on startup to see if the noise is affected by cylinder pressure. If it's a lower end noise (unlikely) it would usually be affected by the removal of spark lowering the cylinder pressure. Carbon rap, however, is usually not dramatically affected by removing spark and neither is a valve lineup noise affected by removing spark.

Spyder
11-30-04, 03:03 PM
How about on mine...where the first start of the day, when its 40 or below out, will go tap tap tap really fast, then stop...only a fraction of a second, but its there...If I let it run for a few seconds, then shut it off, then start it again, its not there, and its not there if the engine gets to operating temp and is then shut down for hours and hours...only that first time on really cold mornings...I havn't been too worried about it, as I figured it was the floating pin, but reassurance would be nice. :)

Anthony Cipriano
11-30-04, 03:22 PM
How about on mine...where the first start of the day, when its 40 or below out, will go tap tap tap really fast, then stop...only a fraction of a second, but its there...If I let it run for a few seconds, then shut it off, then start it again, its not there, and its not there if the engine gets to operating temp and is then shut down for hours and hours...only that first time on really cold mornings...I havn't been too worried about it, as I figured it was the floating pin, but reassurance would be nice. :)


It sounds like the floating wrist pins. The key to identifying the floating pins as the noise source is the 5 to 10 second delay after starting before the noise starts - then stops. Valve tapping (or the SHLA) will start almost immediately after start where the piston pin noise takes 5-10 seconds to fade in.

Spyder
11-30-04, 06:11 PM
nahh...my sound is instant, probably before the starter even disengages completely...then by the time the engine is idleing, its gone...less than half a second after turning the ignition its come and gone, I would say. I DO need a new ISC motor...which I plan on doing ordering on thursday and replacing on the weekend...it idles high and clicks and buzzes and is annoying...causes the temp to run up quick when I'm in town, cause its idleing at stop signs and lights at 1100-1200.

Anthony Cipriano
11-30-04, 06:20 PM
nahh...my sound is instant, probably before the starter even disengages completely...then by the time the engine is idleing, its gone...less than half a second after turning the ignition its come and gone, I would say. I DO need a new ISC motor...which I plan on doing ordering on thursday and replacing on the weekend...it idles high and clicks and buzzes and is annoying...causes the temp to run up quick when I'm in town, cause its idleing at stop signs and lights at 1100-1200.

That does sound more like a valve train or SHLA noise. A 2002 Northstar doesn't have an idle speed control motor. It does have an idle air control solenoid, though. If the idle is high you should clean the throttle body first and make sure that the throttle is not hanging open slightly due to deposits or a cruise control link that is adjusted too tight or something else that's possibly holding the throttle. Idle air control solenoids can fail but they're not a common complaint item.

Possibly when the engine cold starts at a normal RPM it might not make the noise as a sudden RPM flare that is too high when cold could cause some valve train noise if the SHLA has to suddenly adjust too quickly due to the higher RPM.

peteski
12-01-04, 12:23 AM
This is what happens when people start their own question on a thread.

Original question was for a 2002 car but Spyder has a 1994 car...
:bonkers:
So, his does have ISC...
:banghead:

Peteski

Anthony Cipriano
12-01-04, 11:17 AM
This is what happens when people start their own question on a thread.

Original question was for a 2002 car but Spyder has a 1994 car...
:bonkers:
So, his does have ISC...
:banghead:

Peteski



Yea, I got fixated on the 2002 situation and I tend to lose track of what car everyone has. :p Spyder. You obviously have the direct acting valve train with the hydraulic direct acting tappets and not the roller rockers with the SHLA setup. The direct acting tappets are a little more prone to startup clatter due to debris or oil viscosity and sudden high RPM on startup. I guess on a 94 if the startup clatter is momentary and always disappears I wouldn't worry too much about it.