Significance

• Buick sales brochures during the 1990's argued that the manufacturing process would be friendlier to the environment. General Motors, like its rival Ford Motor Company, installed intake manifoldsmade from composite plastic material. This helped lead to a trend throughout the 1990s towards enhanced manufacturing efficiency and modular assembly programs.
  
  

Function

• One of the items to come out of that mix was the wide use of coded plastic parts. These plastic parts were made from recyclable materials. The intake manifold cover was one of the most controversial parts involved in this effort. The manifold cover was used widely on the 3.1 litre engine and soon gained a reputation of causing engine failures early within the car's life span.
  
  

Effects

• The intake manifold gaskets would not seal properly and many owners reported that their cars consumed coolant. The leak would typically appear near or under the throttle body area of the intake manifold. The coolant would destroy the intake manifold gaskets from the inside until an exterior leak formed. The leak would occur while the engine was running. The coolant burned off once it reached the hot engine block.
  
  The intake manifold gaskets were manufactured with a nylon silicone material. Gasket material that came in contact with coolant would not hold up. Many technicians at General Motors reported that failures typically occurred at about 20,000 miles. A redesign was ordered in 2004 to ensure the sealing properties were resolved by being a material more resistant to degradation. A new material was used in the manufacture of the new intake gasket.
  
  The plastic manifold has a reputation for cracking which would lead to coolant invading the crank case and contaminating the oil. The composite material would degrade around the EGR stovepipe and major engine failure would be the result if the problem is not caught in time.
  
  

Engine Design Problems

• The problem with plastic intake manifolds on V-type engines, such as the 3.1 liter V-6, is that coolant from two cylinder banks are fed into one thermostat. The angles of the manifolds and the cylinder banks are not at the precise angle which is required to make a seal fit tightly, so when the manifold is bolted onto the cylinder bank, it is in danger of being distorted. Also, the V-type engines generated a lot of heat. Catalytic converters also contributed to a higher amount of heat and that made intake manifold problems more likely to develop. One end of the manifold also had to contend with temperature fluctuations within the coolant.
  
  

Solutions

• Shoppers of used 3.1 liter Buicks, should examine the engine and check for evidence of replacement of the intake manifold. A complete written service history of the car and documentation of the dealer's warranties should be present before the deal is completed.
  
  Current owners of 3.1 liter Buick automobiles should keep a constant vigil on the intake manifold. A visual examination should take place every time the hood is opened. Check for evidence of a leak by shining a strong light on the intake manifold area. Keep an eye on the coolant consumption. If one has to constantly add coolant or the low coolant warning light comes on, the problem has progressed to a critical level. If the above mentioned problems do occur, have a pressure test done on the cooling system by a GM dealer. This will confirm whether a head gasket leak is present.
  
  Copies of the Technical Service Bulletin can be obtained at a GM Dealership. The TSBs involved include bulletin numbers VSS-20030024, dated March 2004, 2003 and 02-06-01-014 dated April 1, 2002. The part number for the new intake manifold gasket is 89017279.