How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29534
Experience:  GM Grand Master Technician 2007. 14 year experience.
Type Your GMC Question Here...
Gm Tech (Cam) is online now
A new question is answered every 9 seconds

I have a 2005 GMC serria with a 5.3 litre engine. approx

Customer Question

i have a 2005 GMC serria with a 5.3 litre engine. approx 200,000 miles. last summer I changed the oil,used synthetic oil as long as I've owned the truck,when I started the truck up I noticed noise from the engine,most likely from the lifters,this was the first time I've heard any noise that indicated any problems come from my engine. then the low oil pressure light came on.Up until this point my oil pressure has always been normal. I had it towed to a local mechanic,friend of my father. He said to replace the engine. That was not an option for me due to the cost.So I replaced the oil pump myself,along with the pick up tube. Read all the notices and warnings about installing the o-ring on properly onto the pickup tube.When I started the truck up again,I immediately heard the same noise from the lifters/engine,and the oil pressure gauge read zero.I decided to remove the driver side valve cover,and start the engine up again to see if there was any oil flowing up the push rods.I did not see a drop of oil any where on the valve train.After further research on the internet I came across another person with a similar problem,their solution was to fill the oil pump with oil and then pack the inlet and outlet with white lithium grease before re installing and that person said they had full oil pressure after starting their engine back up. I followed what they did and when starting my engine back up I had the same problem,no oil pressure at all,and engine/lifter noise. I am out of ideas,I usually never have problems fixing things,but I got to say this has me really stumped.
Submitted: 1 year ago.
Category: GMC
Expert:  Gm Tech (Cam) replied 1 year ago.

Hi there, I am Cam. Can I get your first name please?

I am sorry to hear about this issue. Can you tell me if you found ant debris in the oil pan when you did change the pump?

How long did you run the engine after replacement of the pump?
Did you change any parts on the pick up or relief in the oil pan?
Do you have a manual gauge that you can install and check to see if there is any pressure?

Customer: replied 1 year ago.
I did not find any debris in the oil pan. I ran the engine for a few minutes not too long so i wouldnt damage the engine.I installed a new oil pick up tube. And when it was at the shop originaly they did put a manual gauge on it and there was very low pressure.
Expert:  Gm Tech (Cam) replied 1 year ago.

How low is very low?

Customer: replied 1 year ago.
approx. 10lb
Customer: replied 1 year ago.
mechanic tried changing oil to 20-50 weight to see if it would help with the pressure but it didnt
Expert:  Gm Tech (Cam) replied 1 year ago.

Ok, at idle that is in spec so I am thinking we have another issue. Attached are the specs for this engine.

6 psig at 1,000 engine RPM

18 psig at 2,000 engine RPM

24 psig at 4,000 engine RPM

I am wondering if we have bad lifters then and not the oil pump. When it is running, do you have any misfiring?

Customer: replied 1 year ago.
well what i dont understand is that everything was fine until i changed the oil,then lossed oil pressure and started hearing the lifters make noise.the gauge worked fine in the truck and now it shows basically was back in the summer when it was taken to the shop and the manual gauge was put on,I'm going by memory by what the mechanic said about the oil pressure but he def said it was dangerously low. About the misfiring,it was running a little rough yesterday when I started it up after re installing the oil pump for the second time. Like I said I didnt let it run too long and it has been sitting since early summer. Could bad lifters cause complete loss of oil flow to the valve train? hope I gave you enough info
Expert:  Gm Tech (Cam) replied 1 year ago.

Perhaps its something that was in the filter. What brand of filter did you use?

Customer: replied 1 year ago.
I used a fram filter, the tough guard, I have seen alot of negative things about fram oil filters since installing it. Was there anything special I should've done when installing a new oil pump?
Expert:  Gm Tech (Cam) replied 1 year ago.

No, the pump is a matter of install, fill pan with oil and go from there.

Even priming is not really needed. I only prime the system when installing a brand new engine.

Customer: replied 1 year ago.
I know to get to the lifters on this engine I'll have to remove the heads. Where do you suggest I go from here?
Expert:  Gm Tech (Cam) replied 1 year ago.

Myself I would install a manual oil pressure gauge in place of the sensor and verify low pressure. If so then I would check at the oil filter. If still low then back into the pump to verify its not faulty. If you have oil pressure but the noise remains then I would be looking at lifters themselves. I would also be opening the filter and looking for debris.

Customer: replied 1 year ago.
Well what is your opinion about what I said with the driver side valve train,there's not a single drop of oil coming out of any of the pushrods,and the lifters are making noise. What is that a sign of? What's the chance of all the lifters going bad/failing at the same time?
Customer: replied 1 year ago.
Sorry I forgot,my name is Linus
Expert:  Gm Tech (Cam) replied 1 year ago.

Linus, my worry is that some debris was in the oil filter and plugged up the block. in the picture attached you will see the diagram of how the oil flows.

Customer: replied 1 year ago.
Ok looking at the diagram,I see what you are saying. If that is the case and the block is plugged up,is there a way to unclog it without pulling the motor out,like a motor flush?
Expert:  Gm Tech (Cam) replied 1 year ago.

I would remove the oil filter and the oil pressure sensor. Try pushing compressed air back from the sensor and flush what ever is plugging it from the filter. If you get nothing Then remember the block in the side of the engine block by the filter.

Customer: replied 1 year ago.
Ok I'll give that a try with removing the filter and sensor. But could you elaborate a little more on what you mean about the block in the side of the engine block...
Expert:  Gm Tech (Cam) replied 1 year ago.

Just above the filter is a small block that is a cover with 2 bolts, about 2" long. It's where an oil cooler would attach if you had one.

Customer: replied 1 year ago.
oh,ok I know exactly what you are talking about.Ok thanks hope I'll solve this problem now with what you've explained to me.
Expert:  Gm Tech (Cam) replied 1 year ago.

Please bookmark this page so you can easily navigate back to it so we can continue the discussion. This is done by pressing (CTRL D on PC and CMD D on Mac). You can reply at any time for follow up information regarding this issue, even after you rate the site and I will reply.