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Carhelp4u
Carhelp4u, ASE CERTIFIED TECH
Category: Chevy
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Experience:  ASE CERTIFICATION
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2007 chevy avalanche 5.3 loosing oil not leaking not smoking

Resolved Question:

2007 chevy avalanche 5.3 loosing oil not leaking not smoking no compression loss.   what could be happening?
Submitted: 7 years ago.
Category: Chevy
Expert:  Carhelp4u replied 7 years ago.
How many miles are on this engine? How much oil do you lose over a 1000 mile period?
Customer: replied 7 years ago.
103000 miles . losing a quart from 1000 to 1500 miles
Expert:  Carhelp4u replied 7 years ago.

Gm actually has a bulletin regarding this problem. This could be numerouse items causing for this problem, but here is where you should be starting to diagnose this problem.

 

This may be the result of:

a PCV fresh air hose that is pinched or restricted by plastic casting flash (this would normally be a concern since new, or shortly after engine repairs).

over-aggressive valve lifters (this could develop at any mileage).

plugged PCV baffle drain holes in the valve cover that has the PCV vacuum pipe attached to it (this would normally be a concern at high mileage).

an improperly sealed PCV valve cover baffle (this would normally be a concern since new, or shortly after valve cover replacement).

  1. Inspect the fresh air hose/pipe and all related connections to make sure that no restrictions, such as plastic casting flash or a pinched hose, which may cause excessive crankcase vacuum. Repair the restriction as necessary. If okay, remove the valve cover that has the PCV vacuum pipe attached to it and perform the remaining steps below:
  2. Check for an over-aggressive lifter by monitoring oil flow at the top of each push rod with the engine at idle. It should not be necessary to raise the RPM to check for an over-aggressive lifter. Very little flow should be observed at an idle. It will be obvious if an over-aggressive lifter is present because its flow will be greatly excessive when compared with the others and a great deal of cleanup will be required. Replace any over-aggressive lifter(s) and re-evaluate the concern.
  3. Inspect the PCV baffle drain holes shown below to see if they are plugged with hardened oil deposits. If they are plugged, replace the valve cover, ensure that the customer is changing their oil according to the maintenance schedule in their owner's manual, and re-evaluate the concern. Generally, this would not be a concern until several thousand miles have accumulated.
  4. Inspect the PCV baffle to ensure that it is properly sealed to the valve cover by flipping it over and adding a little oil to the corner of the valve cover as shown below. The oil should stay in place as shown on the 2 outer valve covers below. If the oil drains into the PCV baffle as pointed out on the middle valve cover below, replace the valve cover. Generally, if this is the cause of the concern, it would have been present early in the life of the vehicle or shortly after valve cover replacement.

Important: If Step 3 or 4 leads to valve cover replacement, perform Step 4 on the replacement valve cover before installing it.


Object Number:(NNN) NNN-NNNN Size: SH

PCV Baffle Drain Holes Described in Step 3


Object Number:(NNN) NNN-NNNN Size: SH

PCV Baffle Comparison Described in Step 4

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