Hello I’m new here and I know this forum is geared more towards Camaro /Firebird but since the Silverado has an LS family engine I thought I would ask for help here also.

history:

2005 Silverado LM7 5.3L. 146k miles. Was driving on the highway one day and all of the sudden I hear a shuttering sound then a ticking and tapping sound coming from the engine. I immediately pulled over, checked the oil, oil was full but my oil pressure gauge was reading lower than normal. It was reading right at or just above 20 psi. Since I have had the truck the gauge has read 40 psi and above.

I restarted the engine and did not hear any of the shuttering/ticking or tapping sounds. However the dash oil gauge was fluctuating more than normal.

After doing some research I figured it was the oil pick up tube o-ring. So I ordered a fel-pro o ring and a new pick up tube. I dropped the pan and replaced the o-ring and pick up tube. Found no metal flakes or shaving in the pan and a minimal amount of sludge. Filled it with oil and a wix oil filter, started it up and still same result on the dash gauge. Fluctuating more than normal. Had 40 psi at start up then once warm dropped to around 20 according to dash gauge.

I bought an adapter that goes right above the oil filter on the oil pan and connected a mechanical oil gauge. The mechanical oil gauge showed about 2-5 psi difference than the dash gauge but did not fluctuate like the dash gauge.

I replace the oil pressure sensor located at the top rear of the engine to see if that would correct the fluctuating dash gauge, but it didn’t. This engine does not have a screen under the oil pressure sensor so that wasn’t an issue either.

I did some more research and found that the oil pressure relieve valve located in the oil pump could be sticking or stuck open. Thus dumping oil pressure and causing low oil pressure.

So I dropped the pan again, pulled the accessory drive off and remove the front cover. I replaced the timing chain and installed a Melling M295HV oil pump which is a high volume pump. Supposed to be good for higher mileage engines. Once again found no metal flakes or shavings. I even filtered the oil when it was draining before I pulled the pan.

Now it is all back together. I filled the engine with 6 quarts of oil. I primed the engine by holding the gas pedal to the floor and starting it 5-10 seconds at a time until I saw oil pressure on the mechanical gauge. Started it up and this is what I’m getting:
If you watch the video, you will see the mechanical gauge needle fluctuating at idle and when at a higher rpm even more. This was taken when the engine was at operating temp.

i don’t think this is normal?? I left the red spring in the new oil pump. I didn’t want to loose pressure at higher rpms due to the relieve valve opening. The truck has 4.10 gears and when I travel on the highway, the engine runs at higher rpm.

Im puzzled, I don’t know what is causing this?

Slack in the timing chain? Not enough oil in the pan? Something wrong with the new pump?

 

I'll take a couple guesses to see if it helps. I've seen that some LS oil pans have an oil pressure relief spring/valve so check into that. That other thing I can think of is the cam plate retainer at the front of the engine. I did a cam swap and replaced my original cam plate retainer; it looked like it was way past due to be changed and it's always changed when people do a cam swap. Good luck.

 

Where would the pressure relief spring/valve be located in the oil pan. I don’t remember seeing any valve or spring in the oil pan near the oil filter port. I know the LS engines that have AFM or DoD have a weird spring/valve but that’s at least 2007+ I think.

I didn’t think about changing the cam plate gasket.

 

Maybe this is for newer LS engines, at ~1:30 the guy talks about the pressure relief in the oil pan.

 

HIs 05 doesn't have that pressure valve in the pan. That is the AFM engines that have that. Could be the Barbell in the back of the engine.

 

It’s always a good idea to change the cam plate. That embossed rubber gasket gets smashed pretty flat over time. Easy to feel the difference compared to a new one.