Hive mind: Oil pressure maxing the gauge on startup

2002 Silverado V6 with about 150k well used miles.  Couple of months back, noticed a lifter tick.  Always ran dino oil in it, but decided to splurge and bought Napa full synthetic and a Napa gold filter.  Tick went away, pressure was a little higher than normal (45-50 v. 25-35).  I actually asked here if it could be related to the oil, but assumed it was just the new unclogged filter.  Always used 5w30.

Two days ago, lifter tick was back.  Again, only on startup.  Put about 4 oz of Marvel in it to see if that would quiet it a bit.  It did, but....

Yesterday, on startup, pressure was 40 at idle.  On mild revs, would peg the gauge at 80 and drop to 20 when I let off.  It would swing as quickly as the tach.  Once it warmed up pressure would hold around 35-40. 

Thought I might have sludge or something, so I just did another change.  Still added 4 oz of Marvel.  Still getting high pressure.  Like, to the point, I'm concerned about blowing out the seals. 

1. Didn't think about it until writing this, but could it be the Marvel doing it?  I figured 4 oz in a 4.5 quart motor wouldn't make that big of a difference.  Maybe trying to take care of it was the wrong thing. 
2. Could it be the synth?  I've read the internet rumors about synthetic in a motor that ran dino oil could cause seal issues, but it didn't seem based in fact.
3. I wondered if my pump was going bad, but that would cause no pressure, not too much?
4. Maybe the oil changes have jarred some sludge loose and they're caught in the pump?  I didn't change the oil hot.

I'm now thinking about doing another change, but leave the filter, after it's good and warmed up and then go back to regular dino oil. 

Thoughts?  Ideas?  Suggestions?  I'm baffled.

-Rob

Sticking relief valve?

Have a look at the filter to see if it's bulged the filter case. That usually happens if the valve sticks and causes too much pressure.

Have you checked it with a mechanical gauge yet? Sending units are known to be inaccurate and modern gauges are more like idiot lights with a needle than an actual gauge.

ShawnG said:

Sticking relief valve?

Have a look at the filter to see if it's bulged the filter case. That usually happens if the valve sticks and causes too much pressure.

Have you checked it with a mechanical gauge yet? Sending units are known to be inaccurate and modern gauges are more like idiot lights with a needle than an actual gauge.

I'm not sure there is a separate pressure valve and that it's built into the pump.  Still looking, though.  Filter was fine, no bulging or anything.  I didn't check with a mechanical gauge, yet, but kinda figured it might not be that because of how quickly the symptoms came on and the fact that the gauge does work.  Doing the oil change, there seemed to be more weeping from the front seal, which makes me think it might have too much pressure. 

-Rob

Put a wrench on the pressure sender (usually at the back of the intake manifold) and loosen 1/4 turn and re-tighten.  The sealant GM uses is notorious for causing grounding issues to the block.

Google the resistance you should be seeing at the sender for any given pressure and compare it to the gauge.  Not outside the realm of possibility that the gauge blew a flux capacitor or a thingamajig

And yes, the marvel could be doing it.  That stuff is thick.

rob_lewis said:

ShawnG said:

Sticking relief valve?

Have a look at the filter to see if it's bulged the filter case. That usually happens if the valve sticks and causes too much pressure.

Have you checked it with a mechanical gauge yet? Sending units are known to be inaccurate and modern gauges are more like idiot lights with a needle than an actual gauge.

I'm not sure there is a separate pressure valve and that it's built into the pump.  Still looking, though.  Filter was fine, no bulging or anything.  I didn't check with a mechanical gauge, yet, but kinda figured it might not be that because of how quickly the symptoms came on and the fact that the gauge does work.  Doing the oil change, there seemed to be more weeping from the front seal, which makes me think it might have too much pressure. 

-Rob

Couple of tbings...

1st, the pressure release valve IS usually part of the pump.  There have been failures where they stick closed and make too much pressure.

2nd point.  I don't believe the seals see oil pump pressure.  Knowing how most industrial oil seals work and the applications, I'm pretty sure tha5 anything above about 5 psi of direct oil pressure would blow directly by a front or rear main oil seal.

Feel free to correct me on the seal thing, but I'm pretty sure they don't see oil pump pressure.

It might be time for a good old flush.  Dump a quart of diesel in the crankcase (leave the oil in there, obviously).  Start and idle it for 15-20 minutes.  Don't rev it or drive it.  Then, new filter and oil.  Follow up with another oil change and filter 500 miles later.  That might clean out some gunk in the relief valve and passages to the lifters and kill two birds with one stone.

wvumtnbkr said:

rob_lewis said:

ShawnG said:

Sticking relief valve?

Have a look at the filter to see if it's bulged the filter case. That usually happens if the valve sticks and causes too much pressure.

Have you checked it with a mechanical gauge yet? Sending units are known to be inaccurate and modern gauges are more like idiot lights with a needle than an actual gauge.

I'm not sure there is a separate pressure valve and that it's built into the pump.  Still looking, though.  Filter was fine, no bulging or anything.  I didn't check with a mechanical gauge, yet, but kinda figured it might not be that because of how quickly the symptoms came on and the fact that the gauge does work.  Doing the oil change, there seemed to be more weeping from the front seal, which makes me think it might have too much pressure. 

-Rob

Couple of tbings...

 

1st, the pressure release valve IS usually part of the pump.  There have been failures where they stick closed and make too much pressure.

2nd point.  I don't believe the seals see oil pump pressure.  Knowing how most industrial oil seals work and the applications, I'm pretty sure tha5 anything above about 5 psi of direct oil pressure would blow directly by a front or rear main oil seal.

 

Feel free to correct me on the seal thing, but I'm pretty sure they don't see oil pump pressure.

1- yes, there is a pressure regulator-ish valve in the pump.  There is a bypass valve in the filter in case the media becomes restrictive.  It wants you to still have oil even if it's not being filtered.

2- for the most part, yes.  Any of the oil gaskets are not relative to oil pressure.  It pressurizes the oil itself through the block, but once it is released into the valve covers or oil pan, it's not under pressure and doesn't pressurize the air in those spaces.  You would get more pressure from blowby or a clogged PCV than from oil.  Obviously, oil filter gasket sees hydraulic pressure, but I can't think of anywhere else in that V6 that would.

Excellent suggestions, and lots to try.

That makes sense on the seals now that you walked through it, which makes me feel a little better if I do need the truck between now and when it stops raining I won't blow anything out with high oil pressure.  I like the flush idea and have no issues doing a couple of oil changes.  The Marvel seemed thin, so I wasn't sure if that could be it, but if I do a flush, I'm not going to add it again.  I'll also do the sensor loosen/tighten thing, although at $30, if it's easy to get to, that's still a cheap fix.   I think I've got a game plan.

1. Loosen/tighten the sensor and check.  If that doesn't help....
2. Do a diesel fuel motor flush.  Would an extra quart on top of the fresh 4.5 quarts in be safe? I'm thinking yes because I don't want to thin out the oil too much.  If that doesn't help....
3. Replace the sensor.  I don't think I have a working meter to check and at $30, it's cheap insurance.  If that doesn't help.....
4. Drop the pan and replace the pump.  If that doesn't help.....
5. Sell it for 3x what I paid for it because of the stupid car market and buy a cheap dd..... (Wife's suggestion)

-Rob

I've had good luck with seafood deluding engines, and a couple times stopping lifter tick.

Opti said:

I've had good luck with seafood deluding engines, and a couple times stopping lifter tick.

WTF

I'm guessing that should be Seafoam and desludging. 

Check. It. With. A. Mechanical. Gauge.

Even first year apprentices know this is the first step.

Seriously, do the simple thing first. It rules out a ton of "what if's" and will probably tell you where the problem is. All with about 15 minutes of effort.

ShawnG said:

Check. It. With. A. Mechanical. Gauge.

Even first year apprentices know this is the first step.

Seriously, do the simple thing first. It rules out a ton of "what if's" and will probably tell you where the problem is. All with about 15 minutes of effort.

 

Valid point. Problem is, I don't own one and it doesn't look like any of the parts stores have them to rent. 
Guess it's time to buy a new tool. 
 

-Rob

Curtis73 (Forum Supporter) said:

And yes, the marvel could be doing it.  That stuff is thick.

Marvel or Marvel Mystery oil?  The latter is like water but will clean oiling systems really well when added to the oil in a car.  On a side note I like the smell of that stuff for some reason.  

rob_lewis said:

ShawnG said:

Check. It. With. A. Mechanical. Gauge.

Even first year apprentices know this is the first step.

Seriously, do the simple thing first. It rules out a ton of "what if's" and will probably tell you where the problem is. All with about 15 minutes of effort.

 

Valid point. Problem is, I don't own one and it doesn't look like any of the parts stores have them to rent. 
Guess it's time to buy a new tool. 
 

-Rob

You should be able to buy a mechanical pressure gauge for oil for like 25$ at any parts store.  Buy the actual gauge.  Not a tool.

I have had a pressure relief valve stick on an ancient Ford 460. It blew the canister right off the oil filter, follow shortly by all the oil. Large mess.

Considering the issues with both these sensors and the stepper motors/solder on the cluster, verify with a mechanical gauge before you drive yourself loony.

In reply to Toyman01 + Sized and :

Thats it. predictive text from a phone

Toyman01 + Sized and said:

I'm guessing that should be Seafoam and desludging. 

 

I think you're correct but I like the idea of deluding an engine with seafood.

And, now I want seafood...

Hm. The big block Ford in my truck runs about 80 psi on initial cold start up but then comes down to 30-40 on hot idle and around 60 while driving.

It's never really concerned me until reading this... Mechanical gauge. 

maj75 (Forum Supporter) said:

Opti said:

I've had good luck with seafood deluding engines, and a couple times stopping lifter tick.

WTF

This might Flounder the thread.  Still worth a shot for the Halibut.

dean1484 said:

Curtis73 (Forum Supporter) said:

And yes, the marvel could be doing it.  That stuff is thick.

Marvel or Marvel Mystery oil?  The latter is like water but will clean oiling systems really well when added to the oil in a car.  On a side note I like the smell of that stuff for some reason.  

I might be confusing Marvel for Motor Honey.

Find anything yet?

ShawnG said:

Find anything yet?

Not yet.  Been raining and work's been busy.  One advantage of WFH, I don't have to work on a car until 2 am to make it to work that morning.  Should be able to get to it this afternoon.  I'll update when I figure it out.

-Rob