Oil pressure

[mas84_720]

My oil pressure light just came on and wont go out. I checked the oil and it was a bit low so i topped it off, but the pressure never went low (its 4x4 and has the pressure guage). My pressure sits around 45 at idle and around 55-60 while cruising. This kinda seems maybe a bit high but it has been like that since i bought the truck and no light til today. Also thought the light only came on for low pressure.

 

Any ideas?

 

Also no visible leaks, oil drips, or coolant/oil mixtures.

[datzenmike]

Should come on at 5-8 PSI. Sender may have failed or the Yellow/Green stripe wire to it has some how become grounded. The sender is up under the intake on the side of the block.

[mas84_720]

so the light went out.... first starting flickering on and off then went out completely, then slowly the oil pressure started dropping. By slowly i mean it has been around 45psi since i got the truck, then after light went out the next day it only got to 40, then the next day only 35, and so on then it stayed at about 10psi for a week. I keep a close eye on oil level and its slowly going down, I have had to add a quart a week (maybe 200 miles of driving). I have looked everywhere for leaks and nothing. Nothing in coolant. No visible smoke from exhaust (with this amount of oil loss i would expect to see atleast a little smoke). 

 

Also it had a fresh oil change and filter when i got it.

 

My thoughts now are there was some kind of blockage at first explaining the higher oil pressure and maybe the light sensor was after the blockage reading low pressure. Now it finally pushed through the blockage and i have good oil flow but now where is my oil going? Could i be burning that much oil in the cylinders? Thats alot of oil loss.

 

Any ideas or common fail points on the z24 motor. Its a rebuild motor with brand new head and timing cover (by previous owner).

 

edit: also wanted to add that i did a recent compression check and all 4 cylinders are good at 180-185psi (which i think rules out valve seats or piston rings, which is common cause of oil in cylinders)

[datzenmike]

A blockage won't affect true oil pressure. Oil pressure is set by the relief valve and spring inside the pump. A blockage after the pump could reduce pressure to the system including the gauge which would show this. There is a by pass valve in the block that allows unfiltered oil to push around a blocked filter but at a slight reduction in pressure..

 

 

Have to say filters are cheap, replace it and see if this improves it.

 

If not, then the sender or gauge may be suspect (about $15) You did say flickering light but the gauge read fine. Now the gauge is dropping.... maybe it's cooked?

 

You say rebuilt motor? Some people go insane using RTV on gaskets that don't even need it. The excess is squeezed inside the motor and works it's way to the oil pan. Hell there may be some in the oil pan blocking the pick up screen. Dump it out and look for chunks of red or blue RTV...the favorite of chevy owners. If you find even one piece, this is likely it.

 

200 miles per qt would smoke like a volcano, plugs would be black. Check the plugs for oily wetness. Place cardboard under it and check in the morning for drips. Newly rebuilt motors will use oil (not 200 miles a qt. though)

[datsunaholic]

Loss of oil could be the sender blew out, or that RTV junk or a piece of teflon tape ended up in the sender splitter.

[mas84_720]

Well just drove home from work and gauge is reading zero, like didnt even move, but no light. Are the light and gauge off the same sender? I assumed not because the light is in all trucks and gauge is only in 4x4 but could be wrong. I will do another oil change with filter tomorrow, and will drop the pan and clean it all out as well just to make sure. Gonna check the spark plugs and do another compression check while they are out also. Im hoping this is something simple, just need this to daily drive for 3 more weeks then i get my brand new car and i can really spend some time rebuilding the rest of the truck.

[datzenmike]

Cheaper to change the sender than drop the pan. The 4x4 gauge sender has two wires on it. One for the red dash warning light and one for the gauge on the console. They're about $15. It's possible that there is absolutely nothing wrong and just a faulty sender. 

[datsunaholic]

Sounds like oil has leaked into the sender.  They go bad.