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Higher Than Expected Oil Consumption (Replace Rings and Engine Valley Cover) #01-06-01-023A
Higher Than Expected Oil Consumption (Replace Rings and Engine Valley Cover)
1999-2001 Chevrolet Camaro

1999-2002 Chevrolet Corvette

1999-2001 Pontiac Firebird

with 5.7L Engine (VINs G, S -- RPOs LS1, LS6)

This bulletin is being revised to add model years for the Corvette, information on the LS6 engine and parts information. Please discard Corporate Bulletin Number 01-06-01-023 (Section 6 - Engine).

Condition
Some owners may comment on higher than expected oil consumption. When checked, the oil consumption could be in the range of 400-600 miles per quart (700-1000 km/L).

On the LS6 engine only, the technician may find oil behind the engine throttle plate and in the intake manifold.

Cause
The cause for this condition may be an interaction between the piston rings and the cylinder bore in vehicles that are operated at higher RPMs -- typically manual transmission vehicles driven in a manner where the engine is frequently or consistently operating at greater than 3200 RPM.

On the LS6 engine only, the engine has a unique aluminum valley cover that has composite oil separating baffles and PCV plumbing incorporated. In some cases, the PCV baffle may not be properly sealed to the valley cover, causing oil to enter the PCV system.

Correction
On the LS6 engine only, replace the engine valley cover if oil is found behind the throttle body or in the intake manifold before replacing the piston ring. Refer to Engine Valley Cover Replacement in the Engine Mechanical - 5.7L subsection of the Corvette Service Manual.

A new set of piston rings is currently available through GMSPO. The new rings are part of a complete piston ring kit. Install only the number 2 compression ring and the oil expander ring from the piston ring kit. All other rings in the piston ring kit should be discarded. The original number 1 compression ring and the oil ring rails should be re-used in their original positions on the piston. All pistons should be used in the same cylinder bore.


Important
Do not dress or hone the cylinder bore. Nothing should be done to change the bore finish for this condition. Changing the bore finish may aggravate the condition.


Refer to the Unit Repair Manual for appropriate ring removal and replacement procedure.

The number 1 compression ring and the upper and lower oil expander rails are re-used because they are already broken in for the bore that they are in. The new number 2 compression ring is made with a very sharp edge that will break in quickly.

Changing only the piston rings noted, with no change in driving style, should change oil consumption to an acceptable level. Changes in driving style that reduce the amount of time spent at higher RPMs will also positively affect oil consumption.

In addition to the standard size piston ring kit listed below, a 0.25 mm oversized piston ring kit is available. The oversized piston ring kit should only be used in those rare instances where the cylinder bore size has been machined larger to accommodate the 0.25 mm oversized piston rings.

Parts Information
Part Number
Description
Qty

12568002
Valley Cover
1

88984247
Ring Kit, Piston
8


Parts are currently available from GMSPO.

Grumpy

thanks for the heads up...gotta love having techs around...

SteveL2

Thanks for the info. Today I took my '01 coupe in to start an oil watch, and the first thing they said had to be done was a change to a "newer" PCV valve -- the new one is copper colored, has a very tiny hole on the side opposite the male end, and they said it does not have a valve which was demonstrated to me by shaking it and it did not rattle like a typical PCV valve does. What's now strange to me is I do not see a mention of this in the TSB.

Any thoughts about the new valve?

MDT

SteveL2,

First post that I've seen referencing a PCV upgrade. Do you happen to have a part # for us?

Thanks.
Mark

SteveL2

I don't have it, but I just left a message for my service writer and hopefully he'll call me back with it. Clearly it appeared much more restrictive than the original one. Ironically, I had previously yanked the stock one and put in a modification that also is much more air restrictive, as explained at this site: http://www.fbody.com/members/stevenm...ML/pcv_mod.htm.

But, when I called my service guy, he said he'd be checking to see what PCV valve I had, so before I brought it in I returned it to stock. So, I'm guessing that in effect the upgraded valve accomplishes somewhat what my modification did.

Honestly, if this little valve is the answer, I'd be thrilled, as I certainly would prefer not to have my engine torn down. But, I am a skeptic, so we'll see............................ :seeya

SteveL2

Mark -- my service guy just called me. Here's the part #, for what it's worth: 12572717.

MDT

SteveL2,

Thanks for the quick response on the part #. Be sure and let us know if the switch to the updated PCV gives any improvement.


Mark :seeya