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Docwheelhorse

Ok... who REALLY knows LS GM Motors...

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Docwheelhorse

Hello All,

my 2005 Silverado with a 5.3 LS (190,xxx miles) had an interesting issue.... its not fatal and I'm not worried about it. Did some reading on other forums and nobody really knows what is going on....

This just recently started happening---

 

Start truck ice cold.... oil pressure comes up but will not build beyond 40 PSI even running down highway. No valve noise or any other low oil pressure symptoms... (40 is nowhere near low anyways..)  .

As the truck warms up and gets to operating temp (~195) the oil pressure GOES UP and will be running close to 60 PSI @ 2500 rpm on highway. Idling oil pressure is around 35....

 

I have read that the oil pump is shot---how can a shot oil pump BUILD oil pressure as it gets hotter (?????)

 

I have read that an o ring on the pump output has shrunk and when it gets hot it swells and seals better (plausible I guess...)

 

I have read that there is a check valve in the oiling system within the motor that is sticking open and that when it gets hot it "un-sticks"

 

I have read a whole lot of non-sense from a bunch of yahoo's....

 

So... any GM LS motor experts that know what's going on here? I suspect its not fatal and just an annoyance... but WTF is going on?

 

Thanks Tony

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N3PUY

Did you do an actual oil pressure check with a mechanical gauge screwed into the block?   

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RedRanger

I've got a '08 that has fluctuating oil pressure at times.

Couple things to check:

1.  Have you replaced the oil filter?  I once had a faulty filter that was effecting pressure and even sending off buzzers and lights on the dash.

Changed the oil and filter and problem solved.

2.  There is a pressure switch on the rear top of the engine that gets gunked up with mileage and effects pressure.

This switch has a screen in it that gets plugged up.  As the oil heats up and thins, the oil pressure could get better.

Some guys buy a new switch/sender others take the switch out, remove the screen and clean it and reinstall it.

 

These would be your easiest and cheapest fixes.

 

Bought mine new and have never really been happy with the LS.

Lifters nock and click on start up for quite a while-always have.

Engine uses 2+ quarts of oil per change, yet there are no leaks, no smoke, plugs burn clean.  Done this since new.  GM would do nothing about it.  GM says it's "within normal specs".

The warm idle gets lower and lower as the truck ages.  Originally it was about 800rpm, then went to about 750 after a year or so, then 700, now it's down to about 600rpm at idle?

Add in the fluctuating oil pressure and it's a pain.

Think I have about 140K on mine.

 

I like the truck, but the engine is quirky.

 

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Docwheelhorse

No....I didn't put a mechanical gauge on it--- several people are reporting the same issue... ignoring the "numbers" on the gauge we can assume that the oil pressure is "xx" cold and GOES UP when it gets hot. I was just curious if any GM Techs or anybody knew of this or had an explanation. It doesn't really bother me at all....

 

Everybody on the net complains of the same thing... my oil pressure is XX when cold and GOES up as engine gets hot.... then the internet experts start throwing everything at it.

 

Tony

11 minutes ago, RedRanger said:

I've got a '08 that has fluctuating oil pressure at times.

Couple things to check:

1.  Have you replaced the oil filter?  I once had a faulty filter that was effecting pressure and even sending off buzzers and lights on the dash.

Changed the oil and filter and problem solved.

2.  There is a pressure switch on the rear top of the engine that gets gunked up with mileage and effects pressure.

This switch has a screen in it that gets plugged up.  As the oil heats up and thins, the oil pressure could get better.

Some guys buy a new switch/sender others take the switch out, remove the screen and clean it and reinstall it.

 

These would be your easiest and cheapest fixes.

 

Bought mine new and have never really been happy with the LS.

Lifters nock and click on start up for quite a while-always have.

Engine uses 2+ quarts of oil per change, yet there are no leaks, no smoke, plugs burn clean.  Done this since new.  GM would do nothing about it.  GM says it's "within normal specs".

The warm idle gets lower and lower as the truck ages.  Originally it was about 800rpm, then went to about 750 after a year or so, then 700, now it's down to about 600rpm at idle?

Add in the fluctuating oil pressure and it's a pain.

Think I have about 140K on mine.

 

I like the truck, but the engine is quirky.

 

Huh... well I have been nothing but pleased with the 5.3 in this truck and the 6.0 that was in another Silverado I owned. Only complaint---the 6.0 was thirsty! I haven't owned a 6.2 or one of the variable displacement LS motors yet.  That screen thing sounds like a good explanation----your referring to the sending unit right? Or is the oil pressure electronically controlled somehow????

 

Thanks Tony

Edited by Docwheelhorse

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RedRanger
26 minutes ago, Docwheelhorse said:

No.... several people are reporting the same issue... ignoring the "numbers" on the gauge we can assume that the oil pressure is "xx" cold and GOES UP when it gets hot. I was just curious if any GM Techs or anybody knew of this or had an explanation. It doesn't really bother me at all....

 

Everybody on the net complains of the same thing... my oil pressure is XX when cold and GOES up as engine gets hot.... then the internet experts start throwing everything at it.

 

Tony

Huh... well I have been nothing but pleased with the 5.3 in this truck and the 6.0 that was in another Silverado I owned. Only complaint---the 6.0 was thirsty! I haven't owned a 6.2 or one of the variable displacement LS motors yet.  That screen thing sounds like a good explanation----your referring to the sending unit right? Or is the oil pressure electronically controlled somehow????

 

Thanks Tony

The oil pressure sending unit is on top of the rear of the engine behind the intake.

Once removed, there is a screen in the hole that also needs to be removed and cleaned.

Check youtube for videos on it.

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N3PUY
20 minutes ago, Docwheelhorse said:

No....I didn't put a mechanical gauge on it--- several people are reporting the same issue... ignoring the "numbers" on the gauge we can assume that the oil pressure is "xx" cold and GOES UP when it gets hot. I was just curious if any GM Techs or anybody knew of this or had an explanation. It doesn't really bother me at all....

 

Everybody on the net complains of the same thing... my oil pressure is XX when cold and GOES up as engine gets hot.... then the internet experts start throwing everything at it.

 

 

You know what is said about those who "assume".  So you really don't know if the oil pressure is going up.  All you know is that the little pointer on the gauge in the dash is going up.  

Maybe as the battery voltage increases  the gauge reads higher. 

Or as RedRanger suggested :

1.  Have you replaced the oil filter?  I once had a faulty filter that was effecting pressure and even sending off buzzers and lights on the dash.

Changed the oil and filter and problem solved.

2.  There is a pressure switch on the rear top of the engine that gets gunked up with mileage and effects pressure.

This switch has a screen in it that gets plugged up.  As the oil heats up and thins, the oil pressure could get better.

Some guys buy a new switch/sender others take the switch out, remove the screen and clean it and reinstall it.

 

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Docwheelhorse
6 minutes ago, N3PUY said:

You know what is said about those who "assume".  So you really don't know if the oil pressure is going up.  All you know is that the little pointer on the gauge in the dash is going up.  

Maybe as the battery voltage increases  the gauge reads higher. 

Or as RedRanger suggested :

1.  Have you replaced the oil filter?  I once had a faulty filter that was effecting pressure and even sending off buzzers and lights on the dash.

Changed the oil and filter and problem solved.

2.  There is a pressure switch on the rear top of the engine that gets gunked up with mileage and effects pressure.

This switch has a screen in it that gets plugged up.  As the oil heats up and thins, the oil pressure could get better.

Some guys buy a new switch/sender others take the switch out, remove the screen and clean it and reinstall it.

 

HI, well... an oil change is coming up (5/30 full synthetic with good filter as always)... if I fell enthusiastic I'll look at pulling and cleaning / replacing the sending unit. Oil pressure is rock solid with no fluctuations or "pegged" ---signs that I'm used to seeing when an electric sending unit has decided to retire itself. Tis motor runs so good and silent that I don't have any concerns that I'm loosing a pump etc...

 

Thanks for info--not trying to be a pita.

 

Tony

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WVHillbilly520H

My old 4.8LS had 230k when I sold ,it my GM guy said all the people coming in with oil  pressure issues used off brand filters when changed to GM/ACDELCO they were fixed and after 150k 10w30 whatever won't hurt a thing since clearances have gotten a little bigger just my experiences,Jeff.

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shallowwatersailor

For what it is worth, I've got the 8.1 Liter engine in my '01 2500HD with 52K on it. When I bought it used five years ago, it went through a quart of dino oil every 1000 miles. Then I changed over to Amsoil Signature 5W-30, and a NAPA 1640 filter instead of the tiny GM/Delco filter which allowed me to put a full 7 quarts in the crankcase. Usage has gone up to about 1500 miles per quart. The big block has always been known to use oil. Mileage is between 10-13 mpg.

 

It sounds like the dash oil gauge may possibly have a ground problem.

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WVHillbilly520H

The gauges in the mid 90s and up GM vehicles aren't true gauges anymore they are all electronic analog styled, they have little stepper motors soldered on the cluster, when these go bad the gauges act erratically then just quit working, I had to replace 3 or more in the wife's Envoy or you replace the whole cluster exchanged out because of the odometer it'll need to be done somewhere with access to GM scan/programing tool to put the mileage reading back in, but look on eBay for GM stepper motor kits cheaper to buy the new an improved stepper motors and replace individually or all at home than replace the cluster, also this is all over the 'net just, Google GM dash/instrument issuses ect, Jeff. Hope this helps.     BTW if it was the GM pf47 go to pf52 if it was the pf48 go to pf61 on the filter you get your extra 1/2 qt.

Edited by WVHillbilly520H
text
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squonk

Those sensors are pressure transducers and are effected by temp. I deal in building automation and have issues all the time with them. Same thing. Change the sensor and clean the screen. Have someone connect a pressure tester before installing the new sensor for piece of mind. You may have to "Tee" it in. The computer may disable fuel if it sees no oil pressure.

if that doesn't fix it I'd either go the cluster route, or try to find out if the computer gets the signal and sends it to the cluster. Could just be a software issue.

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WVHillbilly520H

I sorta miss my old 2000 4.8L with 5spd manual transmission(Pewter)  but I have to say that back up camera comes on handy on the '14 5.3L 6spd auto(Blue) and I don't have to wrench on it for anthor 18k miles, I'm sure more electronic gremlins in the future....

IMAG1005.jpg

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KC9KAS

I have a 2003 Z-71 (185,000+/- miles) and the oil pressure will be "0" then peg as high as it will go.

It has an electronic dash and has been replaced once, and it probably has problems again.

I did buy a new oil pressure sending unit, but haven't had it put in....It takes a "special" GM tool OR remove the intake, and I don't want to do/pay for that!

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857 horse

the variable cyl activation engines have a wild looking thing under the intake manifold that appears to be an electronic valley pan...in some circles it is refered to as a VLOAM,,,,,it activates and deactvates cylinders...when cold you may hear lifter tapping...a sign the vloam is becoming faulty....it will damage lifters.camns,,,and at times pistons....bend push rods....

also the little screen under the oil pressure switch....  relace it or clean it....

also under the intake is the knock sensors.........the harness that is connected to both can play havoc.....somthing else to have tested,,or replace....

i dont think the 4,8's had this thing in them......thats why people that had these engines are happy.......same with v-6's....just less power.....

 

sorry if i have addded extra head aches....but these issues do exist......

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JPWH

Interesting topic. I have been considering replacing old faithful but after reading some of these issues I may rethink it some. 

I have a 2000 Silverado ls 5.3 automatic. It currently has 260,xxx miles on it I have a oxygen sensor code that keeps popping up and the a/c has a leak somewhere. It has always had a lifter tapping noise at start up when cold . my oil pressure has dropped about 3 lbs since new but does not use oil between changes. 

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WVHillbilly520H
5 hours ago, JPWH said:

Interesting topic. I have been considering replacing old faithful but after reading some of these issues I may rethink it some. 

I have a 2000 Silverado ls 5.3 automatic. It currently has 260,xxx miles on it I have a oxygen sensor code that keeps popping up and the a/c has a leak somewhere. It has always had a lifter tapping noise at start up when cold . my oil pressure has dropped about 3 lbs since new but does not use oil between changes. 

"Lifter tapping noise" take a flashlight or some kind of light and really look at all the exhaust manifold bolts especially towards the rear of both sides bet 1 or more have broken or desinigrated from rust at least that's what was making on my 2k 4.8L as you can see I replaced the whole truck whether for the better we will see.

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RedRanger
1 hour ago, WVHillbilly520H said:

"Lifter tapping noise" take a flashlight or some kind of light and really look at all the exhaust manifold bolts especially towards the rear of both sides bet 1 or more have broken or desinigrated from rust at least that's what was making on my 2k 4.8L as you can see I replaced the whole truck whether for the better we will see.

I've had cold start lifter noise on my '08 5.3 since it was new.  GM would not do anything about it.  Said it was "normal".

IT goes away after a few minutes of run time.

Most annoying "normal" sound I've ever had in a vehicle.

 

1 hour ago, WVHillbilly520H said:

 

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Michaelzz28

I have  02 that has done that since it was new they told you thearlier right thing it seems to be normal for some of the 5.3 litters  I have never had a problem with the truck and I like you got told the same thing I also checked out quite a few of the over the years biggest majority of them done the same thing 

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JPWH

The lifter tap is annoying. I discovered years ago to turn it off and then restart. No tap on restart. 

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RedRanger
26 minutes ago, JPWH said:

The lifter tap is annoying. I discovered years ago to turn it off and then restart. No tap on restart. 

I'll try that next time.  :handgestures-thumbupright:

Seems worse in cold weather.

Fall 2009 002.jpg

Edited by RedRanger
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TDF5G

I've owned a few Vortecs. 

 

1996 Blazer 4.3 V6 and it ticked just barely when cold.  120,000 miles when I got rid of it.

 2004 Sierra pickup 5.3 , not noise at all.  Had about 90,000 miles when I sold it. 

 

 I currently own a 2000 Yukon 5.3 and it has the ticking lifter sound when it's cold, but I wonder if it's not piston slap as I"ve read about that also.  It goes away in a few minutes when it warms up.  It's always done it.  Has 165,000 miles.

 

Also I have 2004 Silverado 6.0 with 100,000 and no ticking noise at all.

 

Edited by TDF5G

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bizzo15

I have a 2001 Silverado with the 5.3L and more than likely that start up noise is piston slap, it's pretty common on these motors and yes it does sound awful especially after sitting overnight with cold temps.  However even with these quirks the LS engines are some of the most durable small blocks ever made. I will take these issues over the Ford Triton 5.4L cam phaser issues anyday.

 

Here's a youtube video that shows the piston slap noise.

 

 

Edited by bizzo15
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TDF5G
15 minutes ago, bizzo15 said:

 

 

Here's a youtube video that shows the piston slap noise.

 

 

My 5.3 Yukon sounds just like that but it's louder.  

Edited by TDF5G

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WVHillbilly520H

My old 2000 230k mile 4.8 had 2 or 3 missing exhaust manifold bolts/bolt heads and yes on cold start up it sounded exactly like lifter tap/peck 15-30 seconds later the heat sealed up the gasket/manifold and no more noise (other than the flowmaster exhaust) plus mine was a manual transmission some whirring noise from the throw out bearing  but anyways the aluminum heads iron manifold cheap bolts heat cycling ect lead to dissimilar metal corrosion, the 4.2L inline 6 in the trailblazer/envoy platform are even worse for this and know that too from experience on mine, anyways it's really simple to check for missing/broken bolts even if you have to put it on ramps and look from the bottom up before going off the deep end thinking it's internal mayhem, and some of those no name filters including Fram doesn't have the bypass valves to increase pressure during cold start up and the ACDELCO filters aren't any more expensive and are the same if bought at Wally World Advance Auto ect or GM dealer just my experiences, and 10w30 high mileage oils do tend to quell some oil leakage/seepage they are normally conventional/synthetic blended oils....

 

 

 

Jeff 

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RedRanger

So now that you guys jinxed me with this thread, I'm driving home the other day and my oil gauge pegs and the engine light comes on.

 

I picked up a new sending unit and yesterday morning before work I figured 10 minutes and I could swap out the unit...right?

@#$%@#$  truck!

002.jpg

 

After an hour of gymnastics and playing twister under the hood of my Sierra with sliced and gouged knuckles, I finally got the old sending unit out.

Now to install the new one....  Got it lined up and threaded in like playing operation, don't drop it or you'll never see it again.  As I snugged it down, it snapped off nearly flush with the engine block!

#$%@#$%@# GM engineers!

I've got about 1/4 inch of sending unit sticking out of the block.

Even worse, can't get a tool in there to try and remove it because the morons at GM in their lack of mechanical experience put the damn thing behind and below the rear of the intake under the firewall and transmission tunnel while camouflaged under a nest of tubes and wires.  I now have to remove the entire intake system from the engine to hopefully remove the threaded base of the sending unit.

If the threaded base does not come out I'll be really screwed.

 

I'm sure this will be a good 4-8 hour process this weekend.

What a shitty design.

Why are auto engineers morons?

 

 

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