stuck oil relief valve?

muddkatt · February 25, 2018

PVC valve will NOT cause low oil pressure.

Using synthetic oil will not cause oil pressure gauges to read a lower oil pressure than is actually present.

Delco filters are not what they use to be, run a good filter like the Mobil 1.

If the dealer did use 5w-20 oil by mistake, your oil pressure would be reduced.

Chris Bassett · February 25, 2018

Yes I'm aware of the PCV not necessarily causing low oil pressure, but I"m also burning a fair amount of oil somehow.

The low oil pressure is probably something else (like the pick-up tube or the stuck relief valve which I'm think it's got to be one of those). I agree now on the AC Delco filter, so I am going to switch to something else. I am also not going to the dealer for oil changes as there is no need to anymore. I can either do them myself or get them done cheaper by the other shop and they'll use whatever oil and filter I bring them).

swathdiver · February 25, 2018

Oil Pressure, Minimum, Hot:

6 PSI @ 1000 RPMs

18 PSI @ 1800 RPMs

24 PSI @ 4000 RPMs

AFM Pressure Relief Valve - 55-75 PSI Maximum (55 PSI @ 3000 RPMs @ 70 Degrees Fahrenheit.

Check your codes and do the simple things before thinking about the worst things. I do it too.

GhostWriter · February 25, 2018

5 hours ago, Chris Bassett said:

Well, check engine light is on now (no oil light though, no messages on the dash display) so it's going into the shop to be looked at.

An interesting read. Many 5.3 AFM engine owners have asked the same questions. In no particular order, here are some additional things to consider:

1) Before posting, have your local parts store pull the check engine code

for free. Posting without the codes drives us crazy.

2) Your LC9 could be fine, or it might fail - tomorrow. No mention of another

owner in the mix

3) A 2013 should be equipped with an AFM relief valve shield, and a re-

designed L/H (driver's side) valve cover. Together, they help minimize oil-

consumption on your AFM engine.

4) A thorough technician will test oil pressure at the top, and the bottom

of the engine.

5) The pump pulls unfiltered oil from the pan. The regulating valve could

begin sticking at any time.

6) This is a gerotor (over-the-crank) pump. If removed for examination,

your technician should perform a re-alignment procedure.

7) Funny how my "piston slap" seemed to go away after the pick-up tube

o-ring was replaced.

8) Good luck!

Edited February 25, 2018 by GhostWriter

Chris Bassett · February 25, 2018

5 hours ago, GhostWriter said:

An interesting read. Many 5.3 AFM engine owners have asked the same questions. In no particular order, here are some additional things to consider:

1) Before posting, have your local parts store pull the check engine code

for free. Posting without the codes drives us crazy.

2) Your LC9 could be fine, or it might fail - tomorrow. No mention of another

   owner in the mix

3) A 2013 should be equipped with an AFM relief valve shield, and a re-

   designed L/H (driver's side) valve cover. Together, they help minimize oil-

   consumption on your AFM engine.

4) A thorough technician will test oil pressure at the top, and the bottom

   of the engine.

5) The pump pulls unfiltered oil from the pan. The regulating valve could

   begin sticking at any time.

6) This is a gerotor (over-the-crank) pump. If removed for examination,

your technician should perform a re-alignment procedure.

7) Funny how my "piston slap" seemed to go away after the pick-up tube

   o-ring was replaced.

8) Good luck!

1. Yeah I'm going to drop it off tomorrow to have them put a scanner on it. Happened last night.

2. Yes I'm aware of this. The only difference between possibility between a brand new one and a used one is who pays the bill when it fails (GM warranty or the owner). I am the original owner, by the way (purchased new, oil changed every 5,000 miles with Mobil 1). The motor itself seems fine, even with the check engine light on, still runs smoothly and shifts fine (trans fluid is still the same color when they changed it at 60k, and now it has 115k on the truck).

3. I'll have to check, but it probably is.

4. I believe they did this, although I did ask where they did the check and they said by the oil filter, so maybe maybe not, I'll ask tomorrow when I drop it off.

5. I was thinking this too.

6. If you're referring to removing drive components, yes they did mention that to me when we discussed possibly replacing the pump.

7. This is the first thing I'm going to have them check... the o-ring on the tube. But in reality, if they have to go that far, I'll just have them replace the pump, and the o-ring (even if the o-ring hasn't cracked yet, just for good measure while they're in there checking). I will probably ask them to start with the PCV valve. Despite not having a code to work with, I was thinking that a PCV valve that has just cloged enough for the engine computer to pick it up as malfunctioning, would make sense. Part of me says if it was the AFM system or a lifter, I would maybe have heard it, unless of course its stuck in the "open" position (ie. vehicle doesn't go into DoD mode, which might be possible. the light could be something else too, without the code we don't know obviously. Nothing changed mechanically that I can see in terms of drive-ability and engine noise. I don't hear any ticks or tapping, which I think the AFM lifters make when they are stuck or collapsed.

The PCV valve has never been checked or replaced, so I'm thinking after determining the code, that would be a good place to start (as it's an easier repair that I could probably do myself even) and might explain the sudden increase in oil consumption. I don't know if I noted anywhere, but there is NO oil on the ground, and not leaking from the engine, nor do I see any indications out of the tailpipe (it's not to say it isn't burning it, because it could be a very slow burn that could be taken as normal exhaust, but I don't get clouds of smoke on cold startup either). I haven't looked in the air intake system yet though for oil, but I would think if I found oil in there, it would be because of plugged PCV valve more than likely, unless I'm wrong).

Edited February 25, 2018 by Chris Bassett

GhostWriter · February 25, 2018

8 minutes ago, Chris Bassett said:

The PCV valve has never been checked or replaced, so I'm thinking after determining the code, that would be a good place to start (as it's an easier repair that I could probably do myself even) and might explain the sudden increase in oil consumption.

There's no PCV valve, in the traditional sense. Everything's incorporated into the valve cover.

The cover includes a system of baffles, with a drain hole. In the re-design this drain hole was moved closer to the front of the engine to reduce the likelihood of crossover into the composite intake.

Chris Bassett · February 25, 2018

No I'm aware of this. YOu have to replace the valve cover, which is fine (probably would be a good idea too because if it's a lifter problem, they'll have to open it up anyway to at least see).

was this updated cover released after, say March of 2013, because that's when I got the truck and I'm not sure if it has the updated cover or not? (It's never been replaced or removed in the time I've had it). And removal on the driver's side at least, looks to be pretty straight forward from what I can see in videos...) And I guess there's two parts to the PCV system, one in the valve cover we're talking about, and then another part somewhere else (I think in the intake manifold maybe under the plastic cover?)

Edited February 25, 2018 by Chris Bassett

GhostWriter · February 25, 2018

1 minute ago, Chris Bassett said:

was this updated cover released after, say March of 2013, because that's when I got the truck and I'm not sure if it has the updated cover or not?

2011 sounds about right.

swathdiver · February 25, 2018

The new cover is #12642655. Google around for photo comparisons.

If you're going to spend the money to chase this problem you have another question to ask yourself. Is it worth it to you to overhaul the AFM system as well or delete it?

Edited February 25, 2018 by swathdiver

GhostWriter · February 25, 2018

5 minutes ago, swathdiver said:

The new cover is #12642655. Google around for photo comparisons.

Have always wondered what's actually inside there? Something that could be soaked, blown-out, etc?

swathdiver · February 25, 2018

IDK, just thought the changes were molded into the design. Just jogged my memory and looked at some photos. There's a different baffle with different shapes presumably to keep oil from escaping through the PCV.

I was just reading a tech link article/comments and if someone is running a PF48E and experiencing low oil pressure they could switch to the PF48 and recover the lost pressure. Worth a try anyway.

http://sandyblogs.com/techlink/?p=5000

Edited February 25, 2018 by swathdiver
Additional Info

bgbdwlf2500 · February 26, 2018

My 2010 idles around 20psi warm and will get close on some days to 40psi while accelerating but the fluctuation is always between 20 and 40.

Chris Bassett · February 26, 2018

A bit of an update I guess:

Well I sort of figured this out I think. The DoD/AFM doesn't kick in anymore, as it stays in V8 mode now full time, even going slowly (30 mph in town, which it used to kick in and out often in city driving). T his is probably a dream for some people who hate the AFM/DoD function, which is probably a lot people... But anyway, that's what caused the check engine light. But it has been losing more pressure. Now it seem to idle lower (can't say by how much, but it looks like at speed now PSI is around 20-22 at cruising speed [1700-1800 RPM], and it doesn't change much even up to around 3000 RPM there is virtually no pressure change i can see (I know GM docus say it should rise anouther 5-6 psi for every 1000 RPM, but I Don't see that), and given that the AFM has stopped working (from my understanding, it needs oil pressure to activate) this at least partially confirms that there is an oil pressure problem. Now, maybe it's not that bad yet, but I imagine given more time, it may be. Yeah, I could throw more oil in there to bring it up a bit, but I'd also rather not risk blow seals from too much oil just to bring the pressure up.

So we are moving ahead with the pump replacement, O-ring on the oil pickup line (regardless of it's condition), and also checking the PCV system too, as it's never been changed, and that might also explain some of the oil consumption, since there isn't any leaks (it could be slightly worn rings, but I don't see the smoke either that is usually associated with that... although it could be a very slow burn too, and not really noticeable beyond normal exhaust fumes coming out the back. I did leave it inside overnight, and started it up in our work factory (For ventalation reasons) and no excessive exhaust after warming up).

Like I said, it's probably slowly burning oil, but the only two other possibilities require the pan to be dropped and the front taken off, at which point I might as well just spend the little extra and put in a new pump since I'm there basically.

(Actually, we are going to look at the PCV first, but people have told me---probably on here too--that won't necessarily cause low oil pressure, just oil burn--which is one problem I need to figure out--and a check engine light.)

Edited February 26, 2018 by Chris Bassett

Chris Bassett · February 26, 2018

Also am switching the routine a little, and moving away from AC Delco filters (I only had them because the dealer did the oil changes, which is also changing--I'll do them myself). Thought about using Bosche or Mobil 1 filters and going to the high mileage Mobil 1 5W-30 now that the vehicle is 5 years old and over 100k.

Chris Bassett · February 26, 2018

16 hours ago, txab said:

When a code is set, AFM will not activate

Haven't put the code reader on it yet, but this would make sense. AFM is non-functional after the check engine light came on. It has actually since then gone off, but AFM is still inactive. From what I read, when pressure is too low, AFM doesn't activate as it requires the pressure to activate and maintain AFM/DoD 4 cyl mode