Engine/Propulsion System
July, 2001

Subject:  Engine Coolant Consumption or Coolant Leak (Inspect For Material Degradation/Replace Intake Manifolds)

Models:  1995-1997 Buick Riviera, 1995-1998 Buick LeSabre, Park Avenue, 1996-1998 Buick Regal, 1998 Chevrolet Lumina, Monte Carlo, 1995-1996 Oldsmobile Ninety-Eight, 1995-1998 Oldsmobile Eighty-Eight, 1998 Oldsmobile Intrigue, 1995-1998 Pontiac Bonneville, 1997-1998 Pontiac Grand Prix, with 3.8L Engine (VIN K - RPO L36)

This bulletin is being revised to correct parts and labor operation usage. Please discard Corporate Bulletin Number 01-06-01-007 (Section 6 - Engine/Propulsion System).


Some owners may comment on excessive engine coolant consumption, or an engine coolant leak near or under the throttle body area of the upper intake manifold.


Upper intake manifold composite material may degrade around the EGR stove pipe and could result in an internal or external coolant leak.


  1. Follow the upper intake manifold removal instructions found in the Engine Unit Repair Section of the Service Information Manual.
  2. Refer to the arrow in the illustration of the upper intake manifold above.  Inspect the inner diameter of the EGR passage for signs of material degradation.  Degradation will appear as "pitting" of the composite material in the EGR port passage.
  3. If degradation of upper intake manifold composite material is found, replace the lower and upper intake manifolds with the following part numbers:
    • Lower Intake - 24508923
    • Upper Intake - 17113136 (includes necessary upper intake plenum gaskets)
    • Lower Intake Gasket - 12537197
  4. Follow the lower and upper intake manifold installation instructions found in the Engine Unit Repair Section of the appropriate Service Manual.
  5. If degradation is not apparent, skip to Step 7.
  6. Verify the repair.
  7. If no degradation is found, evaluate the vehicle for other causes of excessive coolant consumption as noted in the Engine Diagnosis Section of the appropriate Service Manual.

Parts Information

Parts are currently available from GMSPO.

Warranty Information

For vehicles repaired under warranty, use the table as shown.