oil pressure issues

[Shutterbug]

Just Got an email from Roadie, i guess I know why nobody was giving me any feed back from the post on the trailvoy site, or at least no intelligent feed back anyway, so Thanks for the heads up.

Ill make this short I hope, 2002 EXT 4.2 I6 126,000 Miles last year had Oil pressure switch replaced, asked mechanic, ill call him HACK for now, if he did a pressure check or did he just replace the switch. The discussion that followed gave me the reason his main business is tires and NOT automotive mechanics. this guy with the certifications on His wall told me the factory oil pressure guage was an actual guage and if it was showing 40 psi then the pressure was 40 psi. I did what I could to educate this idiot about the oil pressure switch / PCM relationship and how the stepper motor that drives the oil pressure needle was extrapalated from the data comming into the PCM from engine temp, RPM, ect but he would have nothing to do with it...ok Im done venting...anyway this year the switch started to give my wife issues and the switch was replaced...aginst my wishes...by the same idiot that did it last year...at least it was free...under warrenty...

So the same issue began one block from the shop on her way home...stop engine message, guage going to 0 and back to 40 and then to 0 again...wife called the shop and they said just drive it it's an wiring issue and they could try and find it for $80.00 and it could take forever...sorry venting again...any way I installed a mechanical guage in the spot where the switch was...if you are wondering, the factory guage does'nt have to be plugged in to give the PCM a reading, which is totally back-ass-wards from the way this switch should work...anyway...on to my current issue...

I am or was loosing oil pressure and withing about 10 minuets of starting the engine...funny thing though...if I turned the engine off and back on I would have oil pressure for about 10 minuets...so I changed the oil and filter...then I would get about 30 minuets befor the oil pressure would drop...so I did an engine flush and another oil change and filter and I'm up to over an hour befor the pressure drops...

So my question is this...what should I use to get what ever it is plugging up my oil pick up tube out of the engine without taking off the oil pan? I dont feel there is a mechanical issue with the pump, and I couldnt replace it anyway since I could only find a repair kit for my year and engine size...or am I totally off trail?

 

[super 88]

Just curious - what oil filter are you using?

I hate to say it but sounds like the oil pan has to come off. When the oil pressure drops are there any unusual noises?

 

[The_Roadie]

Sorry I missed your first post here. Now we look as bad as the other site.

I'd use Seafoam in a clean-out process to see if you can de-gunk the pick-up tube.

 

[Mark20]

Amsoil makes a engine flush. Their normal directions say run it through for 15 minutes and then do an oil change. If your pick-up is plugged that badly I don't know if 15 minutes would be enough. I'm thinking dropping the pan is the best way since you can get a good look at the pickup tube and I think there is a screen on it.

 

[Wooluf1952]

Welcome

In case you haven't
heard:
http://gmtnation.com/f5/welcome-gmtnation-com-heres-story-226/

I'd use Seafoam in a clean-out process to see if you can de-gunk the pick-up tube.

^^ I agree.

It sounds like every time you change oil, run time gets longer.

Use the Seafoam and follow their directions about running it for no more than a hundred miles before changing the oil and filter.

It will also help if you would fill out your info. I may have missed it, but do you have a 4x4?

 

[AbsoluteZero]

Based on your mechanical gauge does the oil pressure actually go to zero? Does your mechancal gauge confirm the oil pressure does fluctuate as indicated by the dash gauge? I don't know the actual set point the oil pressure switch uses to indicate zero but assume it's under 12 psi. From what I've read 12 psi @ 1200 rpm is specs.
Also the puzzler is when you turn the engine off and restart you've got pressure again.
A couple off-base thoughts..... the camshaft position actuator uses oil pressure as it's control. If somehow an intermittant gross leak could allow oil to by-pass and reduce pressure.
Also the oil pump pressure relief could have some object not allowing it to shut off.
It looks like the oil pump is in the front of the engine and may not be too hard to get at. Wonder if you could rig up some way to flow solvent thru the pump's inlet port to clean the pickup screen. You could also inspect the pressure relief port and oil pump for wear.
For comparison..... I've got an el cheapo Harbor Freight oil pressue setup on my 03.... (couldn't resist the onsale price of $12) The sending unit is installed in a sandwich adapter that's between the oil filter and attachment block. When first started pressure is in the 70's at 1500 rpm using 5W-30 M1. After the engine is warmed up oil pressure is in the low 50s at 2000 rpm... (this in the only time it agrees with the IP gauge). After warmup pressure is around 40 psi at 1500 rpm and at idle is less than 15. I didn't check the accuracy of the HF gauge and could be suspect at the high and low ends.

 

[AbsoluteZero]

I found a TSB describing a "New Design Oil Pick Up Tube and Front Cover #04-06-01-015 - (05/24/2004)". The pre-2004 pickup design use an O-ring. The new design used a flat seal. May or may not be relavant. The forum won't let me upload a pdf because of size. If you want to send a PM I can email the TSB to use.
I vaguely recall some issues with a leaking pickup tube O-ring. Maybe this is why the change.