stockA4

sorry about that camera glare guys but what do you think? Completely stock engine, has a little slap that never goes away but it still runs great. Keep going?

dixiebandit69

Put a mechanical gauge on it and get back to us. It might just be the sending unit or the gauge.

If that is indeed the correct pressure, I wouldn't worry about it too much as long as it picks up to about 35+ psi by 1500 rpm.

stockA4

Guys I went and hooked up a mechanical gauge from a cheapo parts store and it tells the same sad story as the stock oil sender

I'm getting about 10-11psi at 550rpm hot idle and about 30psi at 1500. It gets as high as 38-40psi at 3-4k and that is it. Like I mentioned before the engine has a constant yet light tap/slap noise at hot idle that never goes away. This is with Valvoline 20-50 oil as well. I replaced the oil pump o-ring already a while back and it didn't change anything so would one assume that the oil pump is worn out? I have a melling 295 on my shelf I can throw at it but I would hate to waste time on it if it's just going to blow up anyway due to whatever damage has already been caused by the lower pressure.

LilJayV10

iTrader: (39)

If you are worried about damage cut the oil filter open. That's going to tell you the most information without tearing the engine apart.

stockA4

I have a magnetic drainplug and it always just has the usual light sludge on it but I suppose I could cut one open. I just pulled the valve covers and found galling / scratches on the top of three of the pushrods at the very front of the motor though so I'm afraid the pressure is just too low and the valve train isn't getting enough oil at idle and the low pressure could be wearing the rings, cylinders, and piston pins prematurely so now I'm not really sure if it's worth throwing a new oil pump at it at all. It still drives great though and just has that little slap/tap at idle. Should I just throw the melling oil pump on it with a new ls2 chain and cross my fingers it lives another 100k?

stockA4

I guess if I'm that far into It already I might as well change the camshaft too, otherwise completely stock 2004 suburban 1500 4x4 L59 5.3 with G80 GT5 (4.10:1 final drive) stock converter original 293k 4L60e and 31.5" tires daily driver

I have all these cams already in good condition on my shelf to choose from and brand new LS6 springs if needed...

Which one would you use and why?

Stock 4.8/5.3 cam 191/190-114
01-04 LS1/lq4 cam 196/208-116
98-00 fbody cam 199/209-119.5
BTR stage III truck. 218/224-113

G Atsma

If you want a nice nudge in power but stock behavior, use either of the two middle ones. Lean towards the LS1/LQ4(also LQ9) cam. Less LSA.
The bottom one will suck the guts out of any low end power which in a truck is not good.

AND0

It's not the oil pump that is worn, it's the engine. Clearances in the bearings have increased to the point where the oil is escaping before it can build up any more pressure. 300k miles, it has been a good life for this engine, but it is getting to the end.....maybe consider replacement.

01CamaroSSTx

iTrader: (3)

I've got a 2003 Chevy 1500HD that just rolled 323,000 and the lowest I've seen it get is around 30 psi hot idle so I'm calling BS on old father time. I have an 05 Tahoe that I purchased used and the first thing I did was give it an oil change. I wasn't happy once I pulled the drain plug only to see clumps of sludge was falling out with the oil that might as well been molasses. I figured I could just keep changing the oils more frequently and it would clear up but not the case. I will say that on a new oil change and filter the pressure was right where it needed to be but within about 1,000-2,000 miles the oil filter would begin to clog causing lower than normal oil pressure. I'd slap a new filter on it and everything was back to normal and this went on for awhile until the screen on the pick-up tube got clogged to the point that I had to drop the pan and remove it to clear the restriction.

G Atsma

Hey it's possible for an LS engine to be shot at 300k miles. Depends on how it was used or maintained.

TA_Freak

You might think about changing the oil pump. Won't hurt anything. My pressures were getting low and I changed mine along with the timing chain, motor mounts....etc. Now at 347,000 miles I idle at 30 psi and 60 driving (hot).

01CamaroSSTx

iTrader: (3)

Well I didn't want to say the N word.

NEGLECT!

99 Black Bird T/A

iTrader: (4)

Valvoline 20w-50 oil?

Why 20w-50 in a stock bottom end engine? Valvoline is excellent oil but that's not the recommend weight oil. The factory didn't set up the bearing clearances for that thick 20w-50 oil.

20w-50 is way too heavy and thick for normal daily driver in a stock bottom end engine my opinion. Recommended weight is 5w-30 or 10w-30. That thin 0w-40 works too.

About 60 percent of engine wear occurs at start up. The thinner recommend oils move quicker and get parts lubricated faster than the thicker 20w50. Synthetic oil flows easier. So a thin 5w-30 or 10w-30 or 10w-40 gets the oil wedge going quicker at start up.

I'd guess this engine has excessive wear and low oil pressure due to extra wear at cold start over a period of time.

No way to really tell without seeing parts etc.

I definitely don't buy father time as culprit. Neglect and or wrong oil seem far mote likely. Ran an old small block Chevy for 389,500 miles and still got 35 pounds at hit idle with 5w-30 Mobile 1 Synthetic. Always used the recommended 5w-30 or 10w-30 oil, no 20w-50 ever. Currently have a 250,000 mile LS1 that makes 40-45 at hot idle with 5w-30 Mobile 1 Synthetic.

Sometimes the pick up screen in the oil pan can get allot of sludge build up and that restriction reduce oil pressure.

FWIW - I'd try an oil change with 10w-30 Pennzoil Ultra synthetic. It has a very strong detergent package. I'd also use a very high quality oil filter. Run 1,500 miles and have oil. Check oil level at each gas fill. Sometimes the oil pressure will creep up as the sludge gets cut and pick up screen clears.

G Atsma

Boom.....

kinglt-1

iTrader: (26)

300k is a good life...rebuild it or replace and move on.

stockA4

Guys I bought the truck this way for cheap knowing it may need an engine because of the low pressure. I put the 20w50 in it because when I drained the oil the first time it was bubbling like a witches cauldron and I didn't have time to change the o-ring. The o-ring only brought the psi up like 5-psi so I said f it and just left the thick oil in there. I've been driving it this way for 4 months and it hasn't blown up yet so that's why I made the thread to help decide what to do with it. I can get a nice 5.3 locally for cheap but I already have all the spare parts on my shelf to upgrade this one so it's not a big deal to change the pump if it would help it live

01CamaroSSTx

iTrader: (3)

Drop the pan to see if its caked with sludge and if so then most likely it has causing on oil restriction at the pickup tube limiting the flow of oil to the pump. I'd also check to make sure the rods still have side to side movement while the pan was off and I'd also replace the oil pump if I was looking to try and squeeze some more out of it and get that thick engine oil outta there and but in some 5W30.

AND0

The OPs use of thick oil to combat low pressure is the right choice.
Clearances too big, thick oil better fills the bigger spaces. If he switches to thin oil the pressure will drop to truly scary numbers.
If you're worried about sludge, try the old oil change with ATF trick. Just don't run it for hard or drive it at all. ATF is about a 5-7wt.

01CamaroSSTx

iTrader: (3)

Putting thick oil in an engine that is already restricted is the last thing you's want to do so keep that in mind also.

LLLosingit

iTrader: (4)

Engines do wear out and at 300,000 it doesn't have to be neglected to be worn out, You can have put 500,000 on an engine that is driven for long periods at highway speed and not excessively worn or you could have an engine that is started several times a day and only driven a short distance or even a police/cab/salesman/utility type use where they sit and idle for extended periods of time worn out with much less showing on the odometer but many more hours running.
I think all vehicles should come with hour meters and odometers, You would have a much better understanding of how the vehicle was used.
I see trucks with well over 200,000 miles and they are only two years old and the hour meter shows almost 5,000 hours. They are salesman trucks that get started in the morning and shut off at the end of a 10-12hr day. They see city and highway use.
A new oil pump wouldn't hurt but it's not likely to help it that much.