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Old 12-05-2017, 03:41 PM   #1
Ol'Jim
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Strange Oil Pressure Readings - '02 HD 6.0

My 2002 HD2500 has over 279,000 miles on it. I have been using full synthetic Valvoline 5W30 oil in it since it had 97K, and I switched from AC Delco filters, to Wix brand not long after that. I believe they are the absolute best oil filters you can buy, well worth the extra $1 or $2 they cost. It has never had any issues with oil pressure. When cold started, it was always around 45 Lbs on the gauge at idle, and would go a hair over 60 PSI as RPM increased, (but I never run it hard when cold - easy on throttle and RPM). When fully warmed up, it normally idles at 40 PSI, and running at highway speed around 55 PSI hot.
Recently, it was almost time for an oil change, (I do it about every 4,000 miles, even though the oil life monitor doesn't come on until it hits 4500-7500 miles). I noticed when leaving home one morning, that it was idling at 40 PSI, and as I eased out on the road, RPM rose to around 1600, the pressure dropped below 40, to maybe 30. I eased way off the gas, and it went up to 40. go to a gas station, checked level, it was full. Back out on the road, I went easy on the throttle, and it was a bit better, would go to 45 PSI unless I got close to 1800 RPM, and it would drop again. After a couple miles more, as the coolant temp reached normal, and the oil began to warm up, the pressure rose to normal levels. When I got to the highway after 7 miles, it was fine. 30 miles later, exit the highway, pressures are perfectly normal. It was not very cold that morning, maybe 50*.
It acted like I had put thick, heavy oil in it, I had seen a car act like that once, where the guy put 20W50 oil in it. (Late model engines with tight clearances need thin oil). So I changed the oil and filter, using the same oil as always, and again, a Wix filter. Next morning, same thing. THen we hit a week of very warm weather, (for late November, lows in 60's, highs in upper 70's). It didn't do it nearly as bad, and cleared up after about a mile. Last night a cold front hit, it was in the upper 40's this morning, and was worse. So now I am concerned that maybe there is a problem with the pressure bypass valve on the oil pump, or in the filter mounting adapter. (Not real familiar with the oiling systems on these LS style engines, have worked on Chevy big blocks and pre-LS small-blocks for 45 years).
Anyone seen this issue before? Any advice? Engine makes no knocking or other unusual noises. Oil still looks clean and clear. Never seen any evidence of sludge in it. The oil on both those changes was bought from same batch at Walmart. Could it have been a defective lot, thicker viscosity than normal? Once the engine is fully warm, there is no sign of any mechanical malfunction, it idles at 40 PSI, even after a 40 mile highway drive at 70 MPH, with air temp in the 80's. And hits 55 PSI cruising at 2000 RPM.
Also does not seem like a gauge or electrical issue, for the same reasons.
Looking for advice and experiences, don't know what to try next, other than another oil change with a fresh batch of oil and a new filter.
Not wanting to pull the engine out just yet.
Thanks in advance for your thoughts and ideas.
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2015 Silverado Crew Cab 2500HD 6.6 Duramax 4x4
2002 Silverado Crewcab HD 2500 6.0 4x4 Sold 281K Great Truck
1970 Chevelle SS454 (Gave to my son 9 years ago for his 18th birthday. Yeah, I know, crazy, right? Thank goodness he doesn't drive it the way I would, -er, did...).
1971 Monte Carlo SS454 Drag Racer. The old girl finally got new paint!
1968 Camaro SS (New race car project). Caged, Tubbed, Back-Half/Ladder Bars. Rolling Chassis (For now).
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Old 12-05-2017, 08:56 PM   #2
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Re: Strange Oil Pressure Readings - '02 HD 6.0

Well with 280k on the engine. Not sure what you are asking. Sounds pretty normal for that high mileage. Defective oil? I doubt it.
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Old 12-05-2017, 10:39 PM   #3
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Re: Strange Oil Pressure Readings - '02 HD 6.0

Put a mechanical gauge on it just to make sure.
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Old 12-06-2017, 07:35 AM   #4
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Re: Strange Oil Pressure Readings - '02 HD 6.0

the oil pressure on my 2000 5.3L with synthetic oil 5-30w is 40-60psi. cold below 40F may go to 65psi. when hot @idle 40 psi. hywy 55PSI...

if the oil pressure goes outside of this range erratically then I would suspect an electrical issue.. sensor/wire/connector.dash stepper motor ..being this high in miles possible engine but oil pressure if worn engine I would think the pressure would be slower in its reading off normal..
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Old 12-06-2017, 11:22 AM   #5
Ol'Jim
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Re: Strange Oil Pressure Readings - '02 HD 6.0

Next step will be to try a mechanical gauge, as Stickman suggested.
j_cAT, how many miles on your truck? It seems our oil pressures are about identical under most conditions.
My first inclination was possibly a bad ground or wiring issue, but then it seems like the gauge readings would always be lower than normal, or fluctuate. Once the oil temp is up to full normal (hot) operating condition, the pressures are right where they always have been, which is what has me confused.

If a mechanical gauge does confirm what I am seeing, I am concerned about what will happen when ambient air temps drop to the teens or 20's, as we get deeper into Winter.
I am trying to think of what would cause the oil pressure to drop as RPM increases.
Putting aside my lack of knowledge on the LS engine oiling systems, I know most (or all) oil pumps have a bypass valve, to prevent excessive pressure from blowing out the filter, or causing other damage. Under normal conditions, fully warmed oil, those valves do not open. Higher RPM gives more pressure, but the thinned-out oil bleeds out past the bearings and through the valve train quickly enough to where no bypassing is needed. Only when the engine is cold and the oil is still thick, do those valves bypass, (and normally only if the engine RPM is raised high enough to create an over-pressure condition).
I once rebuilt a 454 out of a 1973 pickup, that the rancher who owned it was horrible about maintenance, and would not let his vehicles warm up, or drive them easy when cold. This was in Kansas, where winters are very cold. The thing had low gearing for pulling stock trailers, there were no overdrive automatic trans in those days, so RPM at just 55 mph was over 2500 on that truck. He would fire it up, at 10* outside, with dirty oil (the color and consistency of molasses), and immediately jump up to 65 mph or so, going down the rural roads he lived on. He brought it to me one day, lifters clattering like crazy. Oil pressure was really low. Oil level was full, and black. I changed the oil & filter, now the lifters were not as loud, but it was knocking deep (as in main bearings). He offered me 2 months rent free in exchange for my labor. Got the pan off, pulled oil pump, the bypass valve was stuck open. I thought about just replacing the pump, but knew better because of his driving and maintenance habits. Bearings were shot, crank pins were worn egg-shaped/oval on the rod journals. So I figured a new pump would still have left him with low pressure, and knocking.
After he paid the bill for parts, and grumbled about how the truck should last for more than 10 years, I got him to listen to me for 15 minutes. Told him I had done several rebuilds that were still in service over 10 years old, and over 100,000 miles. Explained how bearing oil clearances are the width of a hair. And how even "thin" oil like 5W30 sounds as thick as maple syrup if you grab a 1 quart bottle that has been sitting out in sub-freezing temp and shake it. And how hard it is for the lubrication system to try and push that stuff throughout the engine even at idle speed on a cold day, much less at highway speeds. Then you leave the stuff in there for 10,000 miles, so it is not only thicker, but full of wear particles because the filter mount also has a bypass valve, to prevent disaster when maintenance is ignored, (dirty oil flow is better than no oil flow). So you are forcing thick, wear-producing fluid through those tight bearing clearances, and it is making the path wider. Then when you finally put clean oil and filter on, the clearances are now so loose that you have knocking from rod and main bearings.
He actually wised up, and would let the thing warm up for a few minutes on cold days, and would drive it gently for the first few miles. I insisted on him letting me change the oil & filter after 200 miles, and again at 3 months. After that, he brought it to me every 3-4 months. I told him that cost of a rebuild will buy a lot of oil changes. And if he had paid full labor/shop charges, it would pay for 20 years of oil changes. Last I had heard, it was still running strong after 8 years...
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2015 Silverado Crew Cab 2500HD 6.6 Duramax 4x4
2002 Silverado Crewcab HD 2500 6.0 4x4 Sold 281K Great Truck
1970 Chevelle SS454 (Gave to my son 9 years ago for his 18th birthday. Yeah, I know, crazy, right? Thank goodness he doesn't drive it the way I would, -er, did...).
1971 Monte Carlo SS454 Drag Racer. The old girl finally got new paint!
1968 Camaro SS (New race car project). Caged, Tubbed, Back-Half/Ladder Bars. Rolling Chassis (For now).
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Old 12-06-2017, 12:27 PM   #6
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Re: Strange Oil Pressure Readings - '02 HD 6.0

Quote:
Originally Posted by aleekat View Post
Well with 280k on the engine. Not sure what you are asking. Sounds pretty normal for that high mileage. Defective oil? I doubt it.
I do appreciate the reply, Aleekat. I agree that the chances for a defective lot of oil to get out onto retail shelves is very doubtful. But I don't think it is normal for any engine to have the oil pressure drop as RPM increases. No matter how many miles on it. This one did not do that until very recently.
Hoping it is a gauge, sensor or electrical issue, not a mechanical one.
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2015 Silverado Crew Cab 2500HD 6.6 Duramax 4x4
2002 Silverado Crewcab HD 2500 6.0 4x4 Sold 281K Great Truck
1970 Chevelle SS454 (Gave to my son 9 years ago for his 18th birthday. Yeah, I know, crazy, right? Thank goodness he doesn't drive it the way I would, -er, did...).
1971 Monte Carlo SS454 Drag Racer. The old girl finally got new paint!
1968 Camaro SS (New race car project). Caged, Tubbed, Back-Half/Ladder Bars. Rolling Chassis (For now).
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Old 12-06-2017, 02:07 PM   #7
j cAT
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Re: Strange Oil Pressure Readings - '02 HD 6.0

no way defective oil but the oil filter could be it.. wix I have issues since last year. the company is non responsive to my b*tch about the filter I use no longer fits the 93MM socket . the older filter fit.. then the oil seals leaking on these .. the rubber used is not compatible with synthetic oil . the filter is the XP $12 one .. I now have gone back to pure one purolator ..

so you all beware WIX has these now made in CHINA !!! more crap .. just like the johnson controls "red top" batteries all crap not made here anymore...
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Old 12-06-2017, 03:43 PM   #8
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Re: Strange Oil Pressure Readings - '02 HD 6.0

Sometimes those 6.0l have oil pressure issues due to a seal in the oil pump going out. there are a couple vids on youtube that are very informative on this to repair the low oil pressure. I have not run into this. When I rebuilt my 4.8 I went and got a bunch of new seals and an oil pump from the dealer and asked the parts dept if the pump or the replaceable seals were a common item, they said not at that dealership, but they said it was in other places of North America.
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Old 12-11-2017, 02:07 PM   #9
Ol'Jim
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Re: Strange Oil Pressure Readings - '02 HD 6.0

I am quite certain it is not an issue with the pump, or the oil pick up, because these would both show lower pressure as the engine warms up and oil temp rises and thins out the oil.
Once the truck is warmed fully, oil pressure is exactly right where it normally should be.

This has me thinking j_cAT could be onto something with the oil filter.
Here is my theory, based on that potential problem:

Suppose the filtration media was defective or not correct, (as in too tight of a weave), or some other defect exists that somehow restricts the flow of oil, and so it does not pass sufficient volume of oil through it when the oil is cold and thick, it would act just like a very dirty, nearly plugged filter. As RPM begins to increase, this could build enough back pressure up-stream of the filter, to cause the pressure relief valve on the pump to open. Which then would cause the oil pressure reading on the gauge to drop. When RPM is lowered back to idle speed, relief valve closes, so pressure goes back up, but still below normal.
When oil eventually gets fully warmed up and thinned out, it can now flow through the restrictive filter more easily, and pressure readings return to normal. This would cause the same effect I am seeing now.

The transition from low pressure to normal pressure is gradual, and it takes about 5 miles of easy driving for the gauge to begin reading like it should. This would probably be about the time the oil temp is approaching normal operating temp. Oil temperature does not warm up as quickly as engine (coolant) temp.
I did not have time to mess with the truck over the weekend, but since it has clean oil in it now, I might just swap out the filter this evening, and see what happens tomorrow...
Did not know Wix went offshore with their filter manufacturing. That stinks. I believe their mfg quality is what set them apart from the rest of the junk, so that will be really disappointing if it turns out to be a defective oil filter.
Will update as things move along...
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2015 Silverado Crew Cab 2500HD 6.6 Duramax 4x4
2002 Silverado Crewcab HD 2500 6.0 4x4 Sold 281K Great Truck
1970 Chevelle SS454 (Gave to my son 9 years ago for his 18th birthday. Yeah, I know, crazy, right? Thank goodness he doesn't drive it the way I would, -er, did...).
1971 Monte Carlo SS454 Drag Racer. The old girl finally got new paint!
1968 Camaro SS (New race car project). Caged, Tubbed, Back-Half/Ladder Bars. Rolling Chassis (For now).

Last edited by Ol'Jim; 12-11-2017 at 02:23 PM. Reason: correction
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Old 12-14-2017, 10:53 AM   #10
Ol'Jim
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Re: Strange Oil Pressure Readings - '02 HD 6.0



Quote:
Originally Posted by j cAT View Post
no way defective oil but the oil filter could be it.. wix I have issues since last year. the company is non responsive to my b*tch about the filter I use no longer fits the 93MM socket . the older filter fit.. then the oil seals leaking on these .. the rubber used is not compatible with synthetic oil . the filter is the XP $12 one .. I now have gone back to pure one purolator ..

so you all beware WIX has these now made in CHINA !!! more crap .. just like the johnson controls "red top" batteries all crap not made here anymore...
j_cAT, I just bought a Wix 51522XP Filter from the local O'Reilly store, and it is American made, not Chinese. Hopefully they are all USA manufactured now, and not just me getting lucky finding an old stock filter.
Trying to post a picture of the box...




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-Jim
2015 Silverado Crew Cab 2500HD 6.6 Duramax 4x4
2002 Silverado Crewcab HD 2500 6.0 4x4 Sold 281K Great Truck
1970 Chevelle SS454 (Gave to my son 9 years ago for his 18th birthday. Yeah, I know, crazy, right? Thank goodness he doesn't drive it the way I would, -er, did...).
1971 Monte Carlo SS454 Drag Racer. The old girl finally got new paint!
1968 Camaro SS (New race car project). Caged, Tubbed, Back-Half/Ladder Bars. Rolling Chassis (For now).

Last edited by Ol'Jim; 12-14-2017 at 11:03 AM. Reason: Add Pic URL
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