Download Engine Coolant Consumption/Coolant Leak ’95-97 Buick Riviera – Condition Some customers may comment on excessive engine coolant consumption, or an engine coolant leak near or under the throttle body area of the upper intake manifold. Cause Upper intake manifold composite material may degrade around the EGR stove pipe and could result in an internal or external coolant leak. Correction 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: • Gasket Kit, Upper Intake Manifold — 89017554 • Manifold Kit, Upper Intake — 89017272 • Gasket, Lower Intake Manifold — 89017400 • Manifold, Lower Intake — 24508923 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.