Possible defective AC/DELCO PF46

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GMBoy

GMBoy

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I've got a 2006 GMC Sierra Denali pickup, 13.5k miles. I always run an AC/DELCO filter, never had any trouble before now. Here is what happened: I get in the truck and start it and ZERO oil pressure - gauge at 0, bells and "LOW OIL PRESSURE" signals going off - the whole thing. I immediately shut the engine off and get out. Look underneath, no oil spill, check oil - right where it should be. Start it up again, same thing- no pressure. But I let it run because I do not hear any tapping noises. I rev the engine and them I get full pressure. So, everytime I start it, no pressure - rev engine you get pressure. I'm thinking bad oil pressure sensor, but also thinking of a bad oil filter. I hook up my Tech 2 and check all the parameters etc and see no problems. Now I really think there's something up with the oil filter - like maybe a bad valve or something. So, next morning, start up the truck, no oil pressure, rev it, get pressure and off to work I go. I leave work, same routine. I stop by Autozone, get a new filter. I get home and swap the filter and problem solved. For 2 days now - no more oil pressure issues.

NOW - what do you guys think may have happened here? I am convinced that this was oil filter related - and I am a little dissapointed that an AC filter let me down after I've used them for years in all my cars. Just for some more info - the truck has 3,800 miles on a Mobil 1 oil change in a truck with less than 14k miles so I doubt it was clogged.

Any insight? Thanks everyone! I am not using Delco anymore..
 
When GM's oil pressure sending units go bad though, they don't read zero oil pressure, they max out the oil pressure. I know this because my 98 Corvette currently has a faulty oil pressure sending unit, and my pressure gauge is always maxed out now.
 
If the problem was't the filter. Then why would the problem go away as soon as the filer was changed? You should cut the filter open and check it out. Maybe post some pictures.
 
I agree with Patman. Working for GM (production manager in a plant) I know a lot about our pattern failures and Patman is correct in that the bad sensors err to the high end. I forgot to add that this was the 6.0L 345hp LQ9 engine in case that mattered to anyone.

I do want to cut the filter open and I will do this and post pics - BUT can anyone recommend the best way to do this so you all can see what may be bad? I'm no filter expert here.
 
I had a VW Jetta (1989) with an ADBV that wasn't working properly. It would knock every time I started it up.

I put on a pureone filter, it didn't do this again.
 
Fear and loathing in the shanty!!!!!!!

PF-46 is in intimate contact with the engine.

Only filter used up to this time.

Will peek in here regularly to follow the discourse.

Out of curiosity, reading in past posts, some A/C Delco filters are supposed to be "Heche en Mexico" now.

Curious if your filter is one of those or made elsewhere.

In the words of the immortal governator, "I'll be back."
 
Why don't you put that possible defective filter back on just to see if problem does in fact come back, then cut it up after that.
Couldn't it have been a trapped air bubble in the sender that was released somehow when the filter was removed? The original problem statement said that pressure registered after a rev-up, it sounds like the sender only misbehaved at crank-up. If there really wasn't oil pressure at that time there sure would have been some noises to tell you about it. An air bubble would be compressible and would mask the pressure until the bubble vented..
Looking forward to hearing the solution.
And it's under warranty right?....just in case she blows huh?
 
Well, anything is possible mtnwalker and I never thought about a bubble. However, remmeber this filter has been on the truck for 3,800 miles before this started. You did convince me to get a litte dirty again - I put the old filter back on and guess what - yep - oil pressure problem again. It never got pressure for 5 starts. Took that filter off and put the new one back on and within 1 second, had pressure. Every start after that - pressure was instant. So, I am letting that filter drain again and will cut it open.

Questions:
1. - Which way do you guys prefer me to cut it? Just cut the can off at the base and post pics?
2. How do I post pics on here?? Must I join some picture hosting sight? Wish BITOG allowed posting of pics directly like other sites....

Again - thanks for the inputs - I will look at the box that the new filter came in to see where it was made,obbop.
 
Oh - obbop - this truck has had 3 or 4 oil changes to date with an ac delco filter each time. Not the same filter in use for 13,800 miles.
 
Why are there no engine noises with the old filter being defective and there being no oil pressure?
dunno.gif
 
That's interesting GMBoy,
Kinda looks like you have a guilty filter huh? Make sure you get all this documented with your dealership. If that filter really was blocking flow at startup I'd have thought you'd have heard it for sure, strange things do happen I guess. If there really wasn't any pressure then there probably was some wear/tear until that pressure showed up, problem is it may take a while to really come back and haunt you.
Get it on the books with Chevrolet for sure.
Now I'm really curious what was going on.
 
Peeked at pics but saw nothing obviously wrong but must admit I have never opened one and poked around its innards.

Could the filtration media have been defective in some way causing low flow? Combine that with a bad bypass thingy and.....??????????

I don't have a clue as to what the problem could be. If it is a defective filter I wonder how common that problem may be.
 
If Filter guy were still here, he would say to call the mfg and get a "filter return" kit. They will inspect it and tell you if it is defective. I think it is free. That is what I would do.
 
Since normal "rounding up of the usual suspects" points heavily to the filter in circumstantial evidence ..I'd see where the sender/sensor is tapped in at.

My feeling is that the ADBV somehow got rigid enough to trump the in block bypass valve and that your pressure sender is on the FILTER SIDE of that flow. When you revved the engine, the pressure elevated high enough to open the aforementioned road block and allowed a pressure reading to be indicated to the little man inside the box ..

Your engine was in no danger of oil starvation ...I think your sender/sensor is good until further evidence suggests otherwise.

Naturally, this is all speculation on my part that would allow everything to occur as you describe it ..with the filter being the cause and its replacement the remedy.
dunno.gif
 
If you do not want to send the filter in. Cut the media off of the core. It would be interesting to see what the center tube looks like.
 
Winston,
If there was a bubble in the sender it would act like a bubble in a hydraulic brake or clutch line. You push on the peddle, but the bubble is compressible so the brake pad or clutch doesn't move (as much anyway). In the oil pressure sender a bubble would not activate the sensor as much as liquid oil would by the same action.
It is interesting just how that filter caused that gauge reading/behavior though.
 
I don't quite agree there, mtnwalker. The air bubble isn't transmitting motion where being compressible would effect the mechanism. The clutch master:slave setup isn't pressure dependent ..it's motion dependent and any non-compressible agent would work (even water if it didn't reach 212F and didn't corrode any of the parts). That is, the air bubble is at the same pressure as the surrounding environment.

That being said, I've had oil pressure gauges that have required me to bleed them. This was 30 years ago ..and although I tend to have a detailed memory ...the lost data fragments are automatically filled in when the real data is missing. I've encountered no such situation in any gauges that I use now.

ADBV is still the most likely suspect IF the sender is on the filter side of the bypass valve.
 
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