Pontiac oil pressure can be tricky! Check with your mechanic first but from my experience with my Pontiac use 10w-40 oil in the winter and 20w-50 in the summer. That has produced better pressure in mine.
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Under back seat.
With a Hammer
http://www.modifiedlife.com/1993-pontiac-bonneville-car-stereo-wiring-schematic/
The wheel bolt pattern is 5x115
it has 250 horsepower
The 1994 SSEI is on the overhead counsel.
under the steering wheel on the left side
The most common reason for the harmonic balancer breaking on a 1994 Pontiac Bonneville SSEI is the inner and outer mass is breaking the balancer down. This happens because your engine is running rough or too high of RPM's.
On my 99 SSEi, it was located on the passenger side just in front of the rear wheel.
I have a '93 ssei. It takes 10w30
degradation of the coolant. flush the system and refill it, and all should be well.