Oil Pressure Gauge Bouncing Around

Oil pressure does typically vary with engine speed. Has it always behaved this way? Is this truck new to you? You may have the sending unit going bad or a bad connection if it's changing really erratically.

The pressure should go up a bit as the engine speed increases.

It should not go down much as engine speed decreases though.

As the engine ages, however, the low pressure at idle will get lower and lower as the engine parts wear.

Plugged oil lines can make the pressure go unusually high and the flow unacceptably low.

A mechanic familiar with that engine could tell you quickly.

Unless it's extreme high miles, I would suspect a faulty guage before an engine problem. Those gauges are notorious for acting up.

wrgrs50s wrote:
Unless it's extreme high miles, I would suspect a faulty guage before an engine problem. Those gauges are notorious for acting up.

on the 2003-through at least 2006 the stepper motor that drives the guages has a tendency to go bad. By 100K miles, some small % of owners have one or more gauge that act erratic. On my 04.5, it was the spedo.

symptom is a "sticky" gauge, erratic gauge, slow to respond gauge. Anytime one doesn't act like you expect it should, I'd suspect a bad stepper motor on vehicles of that vintage.

Good news, is that there are sellers on ebay that will sell you a complete set of replacement stepper motors. It's actually pretty easy to replace them, along with ebay seller that will sell replacement lights for the gauges. As long as your in there, may as well replace all the stepper motors and bulbs. All you need is a small soldering iron. It's easy to remove the gauge cluster and get access to the bulbs and motors if you determine that is the cause of your problem. Some of the sellers will sell the parts along with detailed instructions.

The spedo, oil pressure are the two that commonly fail first since they get the most dial movement.

I've done mine along with several other folks kgauges. figure 15 minutes to remove the cluster, 15 minutes to disasemble, 30 minutes to replace all the stepper motors, another 15 minutes to replace all the bulbs, 15 minutes to reassemble, and 15 minutes to replace the cluster in the panel.

Then time for a cool one to admire your fully functioning cluster.

Oil pressure that goes up a bit as rpm increases, and falls a bit as rpm decreases, is normal. Bouncing around, however, not so much. That suggests air bubbles in the line, which brings up the question "have you checked the dip stick lately."

Had a car once that would show 20 psi at idle, and as you drove off, the oil pressure would rise to about 40 psi, and stay there because there was a pressure relief valve regulating it. As you came to a stop, it would drop off again back to 20.

Thank you all. Lots of things to look at.

IIRC GM had issues with the cluster about that time period. If it's just after you started it in cold weather that would be normal.

Clicky

Your problem solved here for $125

ktmrfs wrote:

wrgrs50s wrote:
Unless it's extreme high miles, I would suspect a faulty guage before an engine problem. Those gauges are notorious for acting up.

on the 2003-through at least 2006 the stepper motor that drives the guages has a tendency to go bad. By 100K miles, some small % of owners have one or more gauge that act erratic.

This is it for sure. A completely common problem on GM gauge clusters.

KJ

My IHC IDI7.3 is supposed to be running around 10 lbs per 1000 rpm. So you may or should see an increase for some motors. I saw a similar gain on my 96 GM 6.5 and 05 dmax.

BUT, as also noted, GM did have some instrument cluster issues. Have it in my 2000 older body C2500, and was showing signs in the 05 when I got rid of it.

marty