Readings such as this one are normal for an LS1 C5. If yours is showing much higher numbers for no readily apparent reason, there’s a good chance the OPSU has failed.
If you're a C5 owner, there's a good chance you like to put your foot down every once in awhile. After all, driving a 345hp sports cars sometimes calls for a little speed.
1. The OPSU is located at...
1. The OPSU is located at the back of the engine compartment, under the intake manifold. Removing the manifold will be the most time-consuming part of the job.
Let's assume you've waited for the perfect moment. You look around, and the coast is clear. Your fingers grip the steering wheel a little tighter, and your right foot is primed to slam down on the Vette's rubber-covered loud pedal.
But this time, things are different. Instead of locking onto the rapidly blurring scenery ahead of you, your eyes are glued to the oil-pressure gauge. Rather than its usual reading of around 40 psi, the display has climbed into the 80-psi range.
As your foot instinctively comes off the gas, the obvious question forms in your mind: What broke?
The good news is that the problem is most likely ascribable to your Corvette's oil-pressure sending unit (or "OPSU," in mechanic-speak), which commonly fails on the '97-'04 models, and not to some major underhood catastrophe.
"Every time we've had a [C5] Corvette in here with the oil-pressure reading high, the cause has been the sending unit fouling out," says a tech from Jim Phillips Automotive Service in Lubbock, Texas. "So we just replace that to start, and if it doesn't fix the problem, we go from there. But in every case it's worked."
With the shop gearing up to perform yet another C5 OPSU replacement, we grabbed a camera, a pen, and a pad of paper, and set out to document the job. Follow along as we take you through the process, which should consume around two-and-a-half hours using standard hand tools.
2. Begin by removing the plastic...
2. Begin by removing the plastic coil covers and unplugging the fuel injectors from their harnesses (shown).
3. Remove all the sensors,...
3. Remove all the sensors, including those for the drive-by-wire system (shown) and idle air temperature (IAT); both are located on the driver side. Also disconnect the mass-airflow (MAF) sensor, which can be found ahead of the throttle body, and the throttle-position sensor (TPS), which is mounted on the front of the engine near the pulley.
4. Use a 5⁄16 nut driver to...
4. Use a 5⁄16 nut driver to loosen both hose clamps and remove the air-intake tract.
5. Remove the fuel lines,...
5. Remove the fuel lines, preferably using a specialized disconnect tool to minimize discharge. Have a rag or shop towel handy to catch any fuel that may remain in the lines.
6. Remove both the front coolant...
6. Remove both the front coolant lines using pliers. Some coolant will spill out, but the loss should be minimal on a cool engine. The line under the throttle body (shown) can be tough to get to. Try loosening the clamp and gently tugging on the hose to dislodge it.
7. Next, remove the 10 intake...
7. Next, remove the 10 intake bolts. The two under the cowl area are difficult to reach; you’ll most likely need to use a wrench or small ratchet on them.
8. Be sure to make a note...
8. Be sure to make a note of everything you’ve disconnected along the way. This tiny vacuum line, for example, is very easy to overlook during reassembly.
9. This sensor will also need...
9. This sensor will also need to be unplugged. It’s located right above the small vacuum line in the previous photo.
10. Next, use pliers to disconnect...
10. Next, use pliers to disconnect the brake-booster hose, as shown.
11. You should now be able...
11. You should now be able to lift the intake manifold out of the engine bay.
13. With the OPSU unplugged,...
13. With the OPSU unplugged, you can see that the connector is covered in oil—almost certainly the cause of the malfunction. While we used a special 11⁄16 socket to remove the unit itself, you should be able to get it out with a standard wrench.
12. With the intake off, the...
12. With the intake off, the OPSU is visible. Note the coating of oil and grime on and around the unit.
14. Since you have the intake...
14. Since you have the intake off, it’s a good idea to go ahead and clean the intake valley. After removing loose debris, we used carb cleaner to detail the area. Strongly consider stuffing rags in the intake ports to keep loose gunk out of the engine.
15. You should also take this...
15. You should also take this opportunity to inspect—and, if necessary, replace—the intake gaskets. Ours were structurally sound, so we gave them a good cleaning and left them in place.
16. With everything tidied...
16. With everything tidied up, it’s time to install the new OPSU.
1.7 Before you do so, be sure...
1.7 Before you do so, be sure to thoroughly clean the oil out of sending-unit plug.
18. Install the new sending...
18. Install the new sending unit, and you’re ready to button up the engine. Reinstallation is the reverse of disassembly—don’t forget those vacuum lines.
19. When you get to the intake-manifold...
19. When you get to the intake-manifold bolts, keep in mind that they’ll need to be tightened to a specific torque level, and in a specific sequence. The precise specifications may be found in a shop manual, or, as in our case, obtained from Alldata. Vette