Zero oil pressure

[Eightball]

I have an 05 trailblazer with 5.3, In the morning when I start it I have no oil pressure and engine rattles, if I increase the RPM the oil pressure goes up and noise stops, if I let off the gas the pressure goes back to zero and it rattles, After it warms up a few minutes its normal and fine the rest of the day, I went to dealer and they told me to have the engine flushed which I did and that didn't help, Should I replace the pump or is there a different fix, It has 155.000 on it, Please I need some answers on this thing, Thanks guys

[chas0218]

First thing you need to do is stop running it until you can get another gauge on it to verify it is the oil pressure and not just the gauge.

[Eightball]

Thanks Chas0218. Its not the Gauge or the oil pressure switch, I had that changed, The engine rattles in the morning but after it warms up its fine the rest of the day, Its just in the morning when I have the problem, I am looking for some way to fix this problem without having to take the whole front end apart as its a 4x4, Its a huge job to replace the oil pump, Looking for suggestions.

[gmtech4]

are ya looking for a magical solution to a difficult job,,,,,,doesnt work that way ,,,,thou you can pay someone to do it for you ,,,,

 

not sure what else to tell ya brian,

 

oh and driving it will make the $$$$ go up

[Eightball]

An answer like that wasn't really necessary was it?? All I was really asking is if maybe there might be something else wrong other than the oil pump, I can do the job myself, And no, Im not driving it, Its in my shop as im replacing the heads.

[gmtech4]

what else could it be ???? just sounded like you where being lazy thats all,you have service information to diagnose it further if your,,,a tech

 

so i said that ,,

 

i will gladly post a diag sheet for it if ya like brian

[Eightball]

Im 55 years old and retired, No, Im far from lazy, Ive been there done that and came back for more, No, Im not a tech, But I can read and all I have is a repair manual, Ill get the job done, I just didn't want to pay a dealer 3 grand for doing it. Like I said, I was just asking a question as to weather or not it could be something else other than the oil pump, I already have all the parts, I just didn't know if I was missing something, I didn't think my original question was that misleading.

[jott5555]

Everyone says dropping the pan is a huge hassle. All I see is disconnect the front drive line and axels (leave them in the hubs). Drop the axel drop the cross member and starter and the pan is easy pickins. Am I missing something?

[DamonLee22]

O ring in the oil pump pick up tube has failed or deteriorated allowing air to be pulled into the tube, and oil has a difficult time getting pulled up the tube.. Usually only occurs on a cold start and then will be fine the rest of the day. After the pump picks up the oil, it will stop most of the air from entering the tube, but pressure may run a little lower than it normally does.

[Eightball]

Thank you Lee for that answer, I will replace the o-ring, This Trailblazer has been everything except good, Its been one thing after another.'Again, Thank you

[DamonLee22]

Supposed to be like a three hour job.. If you decide to replace the pump itself, which requires removal of fan, coolant, water pump, harmonic balancer, timing cover, oil pump, and oil pan.. It's more like five hours.

[Eightball]

Im going to replace the pump, I have to drop the pan anyway to get to the pickup tube so might just as well do it all. Im going to replace the timing chain and gear as well. I should have just pulled the engine, Its all apart anyway, I had a blown head gasket so I got the heads done, The engine is still apart, This has turned into a diffacult job, But ill get it done, By Spring, lol.

Thanks Lee for your help.