High volume oil pump 98 K1500 5.7

[L31MaxExpress]

I use stock volume big block pumps in every small block I build and have for more than 10 years.

 

[georgedunham]

I believe that there are about 100,000 miles on this motor.
I believe, because about 4.5 years and 20,000 miles ago I bought it sight unseen having been told it was an 80,000 mile motor.
I jumped to a number of wild, irrational conclusions when the oil pressure started triggering the check gages light more readily.
The original engine wore out (knocked, shook, overheated) at about 190,000.
I thought that the piston rings nearest the crankshaft were oil scrapers.
That’s what I was referring to.

 

[Road Trip]

I believe that there are about 100,000 miles on this motor.
I believe, because about 4.5 years and 20,000 miles ago I bought it sight unseen having been told it was an 80,000 mile motor.
I jumped to a number of wild, irrational conclusions when the oil pressure started triggering the check gages light more readily.
The original engine wore out (knocked, shook, overheated) at about 190,000.
I thought that the piston rings nearest the crankshaft were oil scrapers.
That’s what I was referring to.

George,

Good reply - I have a better grasp of what's going on in your engine bay.

And the good news is that the photo of the plugs you pulled would tend to support
the 80,000 (purchase)/100,000 current estimated mileage on the current engine.

As for why you have excessive clearances on your bearings, there are several
variables we would have to consider, including:

* Original build (or rebuild) quality?
* How often were the oil changes performed by the PO?
* What kind of driver(s) operated the engine before you purchased it? Elderly
couple who drove it gently to the church & the farmer's market? Or did Dad
drive it normally, but when borrowed by #1 son it was driven as hard as only
a motivated teenager can manage to do? Why was the engine available for sale?
Previously mentioned teenager pit-maneuvered by the Arkansas Highway Patrol
after an extended chase...leading to the insurance company totaling the vehicle?

The point I'm making is that depending upon exactly how the engine was treated
by the PO, we could wear out none, some, or all of the engine. For example, thanks
to a poor cooling system (yet at the same time high quality synthetic oil used) I've
seen cracked cylinder heads from overheating, yet the engine still shows very good
oil pressure.

****

Thanks for your clarification on the scrapers. Based on your spark plug photo, I
would concur that your oil rings are still working properly. And in order to preserve
the status quo and not upsetting the delicate balance/interplay inside your engine, my
conservative recommendations are based upon a tried-and-true "Measured Response"
approach. So instead of me just saying a blanket 'no' to the high-volume oil pump,
let's try this no-cost mind experiment:

1) Instrument the engine with a mechanical oil pressure gauge. (Done - good)
2) Mechanical oil pressure gauge agrees with dash gauge. (Meaning the
'Check Gauges' circuit isn't be lied to by the oil pressure sending unit. (Done - good)
3) Compression check engine & verify overall health of the 8 combustion chambers. (Done - good)
4) Replace spark plugs & read old plugs for any signs of mechanical failure. ( Done - good)
5) Change oil to higher viscosity in accordance with/meeting Service Manual recommendations. (Done - good)
6) Verify hot oil pressure is good enough for quiet engine operation & 'Check Gauges' light remains out. (To be Accomplished)

7) IF Step #6 gives desired results, stop repair. Monitor for the next 1000 miles/12 months. Revisit Oct '24.
Cost: oil change. Risk: None mechanically. Will require good battery to ensure continued good starting in colder weather.

8) IF Step #6 fails to solve issue, then decision time. In order of preference, my recommendation would be:

8a) Retrofit factory engine oil cooler from the HD cooling version of your truck. (@L31MaxExpress 's recommendation)
Preferably sourced from the Treasure Yard. Pro: Cooler engine oil temp gives thicker oil during
a hot idle. Con: Time, Effort, & Expense could be considerable depending upon if you do this yourself,
or pay someone else to do it. Risk: Used engine oil cooler could have been contaminated by prior
engine failure & would spread this to your engine?

8b) Go for the high volume oil pump. Pro: Good chance this solves the hot idle oil problem.
Con: 100,000 mile rings may or may not be able to handle additional oil splash described in
in post #5...and we turn the engine into an oil burner. Q: How much oil is it currently using?
How much oil does an engine have to burn in order for it to exceed your threshold of pain?
Do you feel lucky?

8c) Decide to install rebuilt long block. Pro: No more worries? Con: $$$$. Can this be
justified given the 1000 miles per year that it is driven?

****

That's all I got. For what it's worth, in a previous life I would be identified as the guy who 'wouldn't sign
off a Code 3 write up' on the flight controls on a F-16, making me most unpopular with those who wanted
the tail in order to meet the mission requirements. I used to tell them *no*, figuring they wouldn't
understand the technical reasons behind my decision. Guess what? This invariably led to more heat than
light shed on the subject. ;-)

This is where I learned to instead give leadership ALL the scenarios, from what I recommended (downtime to
troubleshoot the wiring harness) to what was legally possible per the T.O. (quicker box swap & aircraft passes
follow-on ops checks on the ground.) I would explain my measured response, but then let THEM actually decide
what to do/own the problem.

And then cheerfully follow their orders. And after a few sorties of having the aircraft not get well despite
filling it with 'new/supposedly good' black boxes from other airbases, then they would let me have it back so that I could
troubleshoot the wiring harness like I originally wanted to do in the first place. :0)

Over time, my track record was such that they learned to trust my recommendations, and from that point
forward more light than heat was shed on any Code 3 jet I was involved with.

****

The moral of the story? I needed to be accurate and own my recommendations, and share them clearly with the 'owner'.
But at the same time, I had to learn to let the owner make/own the final decision.

One last thing. If you wanted to run all this by your mechanic who (correctly) asked about the compression test,
I would think that is a great idea.

Apologies for the length. That's all I got. Let us know what you uncover.

Cheers --

 

[Road Trip]

PS: Analyzing stuff like this is hard enough shoulder to shoulder under a raised hood.

It's 10x harder via the written word -- it's easy to deliver the wrong vibe along with the right info.

****

The bottom line is that I enjoy troubleshooting, and simply want to
give you what you need in order to make an informed decision.

The goal? That between the all of us we maximize the pain/gain ratio.

Cheers --

 

[1989GMCSIERRA]

High volume oil pump on a stock engine is not a good idea. If your current pump is the cause of the low pressure issue then a stock replacement will do. If your clearances are that bad a high volume/pressure pump won't save you.

This right here.

 

[SableSlayer]

If you end up pulling your oil pan to do anything inside the pan I would recommend changing out your connecting rod bearing the main bearings while you're in there. I just did that on my 98 and cleaned out the pump also along with replacing the pump to distributor rod with a melling that has a metal coupler on it. The stock oil pump rods have a plastic coupler that's known to fail.
Since doing all this my l31 with 230k miles has been running 40 PSI cold idle 28psi hot idle. Doing the bearings with the engine installed take wasn't bad at all.

 

[georgedunham]

I’m driving the truck to work tomorrow, so it should get about as hot as ever. But I’m pretty confident that the idiot light will stay off, and noise hasn’t been an issue (should have mentioned that earlier)
About sableslayer’s comment, I was wondering about that.
Thanks for sharing your experience.
I’d rather not take the pan off, but when I’m in there-

 

[Moleman]

Ran this motor like this from work one night.no oil pressure.

 

[georgedunham]

Unfortunately, the oil pressure dropped to a level that triggered the check gages light.
I think I will look at the alternative oil cooler next.
More than a little bummed, but not at all surprised.

 

[Road Trip]

Unfortunately, the oil pressure dropped to a level that triggered the check gages light.
I think I will look at the alternative oil cooler next.
More than a little bummed, but not at all surprised.

Q: What was your mechanical oil pressure reading when the check gauges light came on?

1) Are we close to good enough for 1000 miles/year, or is this engine so bad that it
should be parked? (You mentioned a hot idle of 12 psi in Post #1 before changing anything,
so I'm thinking the former vs the latter, especially given the reported lack of bad noises.)

For what it's worth, there's loads of SBCs still serving/serviceable with 10 psi of oil pressure showing
at a hot idle. (As long as the oil pressure still comes right up with rpm.)

2) Let's say that you have 12-15 psi of oil pressure at a hot idle and the Check Gauges lit
is on. If this is the case, I'd be suspicious of a 'false positive' by the light itself? I checked
the Service Manual, and they do not specify any specific oil pressure for this light to illuminate?
Or what specific coolant temp for that matter, for either reading 'out of bounds' will cause
this light to come on?

****

I think your plan to implement an engine oil cooler is both a good idea for your current
engine + will future-proof your engine bay for the next powerplant. (ie: make it easier
for your next engine to last a good, long time. {Referring back to Post #39 by @L31MaxExpress.})