Temperature, Ground-Out, Accessory Load

Flat Spots On Tires  - Tires which have sat and been cool for a time can develop flat spots.

Irregular Wear On Tire Treads  - Tires which have sat and been cool for a time will be stiffer and any irregular wear conditions will be more noticeable than they will be once the tires have warmed and softened.

Exhaust System Growth  - Exhaust systems may exhibit a ground-out condition when cool which goes away once the system hot. The opposite may be true that the exhaust system is fine when cool but a ground-out condition occurs once the system reaches operating temperatures. Exhaust systems can grow by 1-2" (2.5-5 cm) when hot.

Engine-Driven Accessory Noises: 

1. Belt Whipping - An engine accessory drive belt, or belts could exhibit a whipping condition if a belt is deteriorating and deposits are building up on the underside of the belt.
2. Loose Mounting Brackets or Component Ground Out - Engine driven accessories such as a generator, a power steering pump, or an air conditioning compressor could exhibit noise conditions due to either loose mounting brackets or due to related components of the system in a ground-out condition during certain operation of that accessory system.
3. Cold or Hot - These accessories could exhibit noise conditions when cool which go away once they are fully warmed-up, or the opposite may be true.
4. Load on an Accessory Component - These accessories could exhibit a noise condition while under a heavy load, perhaps when combined with a cool or fully warmed-up condition.
5. Bent or Misaligned Pulleys - Bent or mis-aligned pulleys in one or more engine-driven accessory systems could contribute to a noise or vibration condition.
6. Fluid Level in Accessory Systems - These accessories could exhibit a noise condition due to an abnormal amount of fluid contained in the system of which the accessory is a part.
   • An improper power steering fluid level could produce noises in the power steering system.
   • An improper air conditioning refrigerant level or an excessive amount of refrigerant oil could produce noises or possibly vibrations in the air conditioning system.
7. Incorrect Fluid Type in Accessory Systems - These accessories could exhibit a noise condition due to the incorrect type of fluid contained in the system of which the accessory is a part.