It is important to have a diagram when changing a belts on a car. The belt diagram for this car can be found under the hood on a stick or in the maintenance manual.
Under your hood there should be a diagram. a sticker on top of the radiator...in that area. If not you could probubly google "Belt diagram for 1998 buick regal" image search. make sure you get the right diagram for you motor.
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The popping noise from a Buick Regal could be one of several things. You could have brake issues, or some problem with the suspension. Left unimpaired, the car could break down at any time.
Some of the places a person can find Buick Regal parts are JC Whitney, Autoparts Warehouse and also from the Buick store itself. Another option is through a pick and pull company.
Could be the resonator
The thermostate could be bad or a air pocket somewhere in the cooling system wont let the coolant circulate properly,
first thing to check is the fuse
Could be a bad thermostat or heater core
could be the crank sensor, the go out. the have a reputation for that.
Vehicle Speed Sensor
Could be a bad thermostat or heater core
I have a Buick Regal LS and I had them run a computer diagnosis and it was due to the gas cap not fitting properly. There is an electronic sensor there. Most automotive stores will do this check for you free of charge.