If you see something similar...
If you see something similar to this on your C5 instrument cluster when the motor is not running, chances are pretty good you have a bad oil pressure sending unit.
My first indication that there was something radically wrong was when I glanced at the instrument cluster of my C5 after turning the key to "on"-before starting the engine-lo and behold, both the analog oil pressure gauge and the digital readout on the cluster said my oil pressure was a whopping 73 PSI-and the motor wasn't even running. Obviously, something was grievously amiss under the hood, and my first suspicion was that the oil pressure sending unit had given up the ghost.
Upon doing a bit of research on the Internet, my initial diagnosis proved to be correct; apparently, this early-death syndrome of the oil pressure sending unit was a fairly well known and not-too-rare occurrence with '97-'99 C5s. From what I read on forums, blogs, and other sources, some other owners with the same affliction simply opted to drive their C5s as-is without fixing the problem. While this is indeed the easy way out, if something else should go awry with the engine, you won't get any early indications without a proper-functioning oil pressure system. Nope, that's not for me; my credo is simply that if it's broken, then fix it.
Here's the oil pressure sending...
Here's the oil pressure sending unit. The AC/Delco part will set you back about $20, whereas you can get a NAPA replacement part for about half that price.
If you elect to have the work done by the local garage, be prepared to spend between $150 and $200 for the job, plus the price of the sending unit (about $20 additional); or do it yourself and pocket the cash. Here's what it takes to do this job. here.
Time: about 3 hours
Tools: sockets, swivel socket attachment, screwdriver, wrenches, pliers, lock-grip pliers, torque wrench
Torque Specs
Intake Manifold Bolts (First Pass in Sequence) - 44 lb/in
Intake Manifold Bolts (Final Pass in Sequence) - 89 lb/in
Fuel Injection Fuel Rail Bolts - 89 lb/in
Throttle Body Bolts - 106 lb/in
Oil Pressure Sensor - 15 lb/ft
Engine Wire Harness Clip Bolt - 37 lb/ft
Engine Wire Harness Ground Strap Bolt - 37 lb/ft
| Difficulty Index - 2 Wrenches |
| Anyone’s Project: no tools required | 1 Wrench |
| Beginner: basic tools | 2 Wrenches |
| Experienced: special tools | 3 Wrenches |
| Accomplished: special tools and outside help | 4 Wrenches |
| Professionals Only: send this work out | 5 Wrenches |
Start by unscrewing the airbridge...
Start by unscrewing the airbridge where it connects to the throttle body, then unscrew the clamp that connects the MAF (mass air flow sensor) to the air filter assembly (in my case, it's a Black Wing cold-air induction filter). Then remove the whole tube/MAF assembly and place it out of harm's way.
Disconnect each wire harness...
Disconnect each wire harness that connects to the eight injectors; simply push upwards on the metal clip on the bottom of the harness, then pull the harness off the injector. Pull the big vacuum hose off the brake booster at this time as well.
Disconnect the sensor plugs...
Disconnect the sensor plugs from the throttle body and pull off the coolant line going to the bottom of the throttle body. Use a pair of lock-grip pliers to pinch off the coolant hose so you don't lose liquid. Then remove the remaining hoses and connectors going to the front of the intake manifold.