Serpentine Systems

• Traditional V-Belt systems use a series of thin rubber belts about as thick as they are wide. These belts wrap around the outside of the crankshaft accessory drive pulleys, and are prone to stretching and working loose with age and centrifugal force. A serpentine belt system uses a thin, wide belt which is ribbed longitudinally on one side and is smooth on the other. This belt winds through the pulleys, driving some with the ribbed side, and some with the smooth. A spring-loaded tensioner pulley keeps the belt tight.
  
  

Serpentine Belt Drawbacks

• If the serpentine system has any drawbacks, it is that the pulleys driven by the smooth side of the belt are prone to slipping loose when wet. Since these flat-side pulleys (including the tensioner) do not use a mechanical centering system, longitudinal and lateral slippage are common.
  
  

Water Splashing

• Since the Deville was an all new car with an all new engine, it comes as no surprise that it has a few bugs. One of these unforeseen glitches lay in the engine's water shield, which is neither long enough nor wide enough to fully protect the belt from exposure. Many serpentine-belt cars from this area have a similar problem.
  
  

Tensioner Weakening

• The belt system's tensioner is a known weak point in older GM engines, since the long term effect of constant heat cycling upon the tensioner spring was unknown at the time. It was assumed when the engine was designed that the spring would see very little heat cycling, but in reality there is quite a bit of oscillation encountered in the course of normal operation. The only way to resolve a weak tensioner spring on Northstar engines is to replace the entire tensioner, which is fortunately fairly inexpensive.
  
  

Belt Symptoms

• Unlike V-Belt systems, a slipping serpentine belt may not squeal at all when loose. Symptoms include overheating at speed, heavy steering, low voltage to headlights and accessory drives and possibly weak air conditioning. Replacement of the engine's belt will help to solve these issues, but a new tensioner may be required.