Dsg2500

I recently picked up a 4.8L G2500 135" cargo van that was a former CAT service truck for a great price. Milage is 225k but idle hours are probably much higher given it's former life. No matter, it's main use will be storing tools, tires, motorcycle and a great project truck to learn to wrench on the legendary LS motor.

Problem with the truck is the oil pressure only gets up to about 16psi at 35-40mph, and drops down to near zero at stops and check gauges light comes on. Seems to run fine if you keep it moving but starts making lifter noise if you let it idle too long, so I'm sure this is an actual motor problem and not the gauges, sensor or sending unit.

My first suspect is the oil pump itself, but have read about problems with oil pickup O ring getting pinched causing it to suck air. Are there any other possible causes for this? I've thought about ordering an Ultra Power M295HV high pressure, high volume oil pump from rockauto for $55, but from what I've seen on Youtube most people use Melling oil pumps, and I've seen one explaining how the Melling unit is better than OEM. Need a front main seal, too. Anything else? Timing cover gasket? Rockauto cart currently has Ultra Power M295HV and Apex ATC3771 front main seal(should I get ACDelco 29602 OEM seal?)

1) Is there any reason to go with Melling brand pump that is twice the price of Ultra Power?
2) Do I need / Should I get an oil pickup assy or timing chain with the pump?

I'm not in any rush and will be getting a Factory Service Manual rather than relying solely on YouTube videos. I understand I need to use a harmonic balancer puller to avoid damaging the crank threads and plan to borrow one from Auto Zone. This van will rarely get driven so trying to keep cost down as much as possible but not if the Melling pumps are vastly superior or if timing chain is .5hr more once I'm in there. Looking for advice, tips and any links to particularly good guides or videos.

Thanks in advance,
Dan

Rednucleus

With that mileage, try a heavier wt oil 1st and see if it bumps up the idle pressure. My 93 5.7 has 350k and running 20/50 vs 5/30 increases pressure about 10 psi

Dsg2500

I read a similar thread where someone recommended running straight SAE 30w or SAE 40w to see if it bumps up the pressure. Is this a good idea? I have never seen straight rate motor oil like that. Or should I try 20w50? Van will live in Southern AZ. Oil in it looks very clean but I have no idea what weight it is.

oldchevy

Back in the day we used to put in STP to thicken the oil on older engines. It looked like honey and did work in most cases. Motor Honey was another good one.

Dsg2500

No offense, but sounds like snake oil to me. Even 20w50 just seems like a band-aid. Increased PSI due to increased resistance to flow does not equal increased flow. I'd rather get this oil pump (and timing chain?) swapped out the right way. Kinda look forward to the wrenching. Found factory service manuals are over $300 so looks like I'm going to have to settle for a Chiltons.

Rednucleus

Curious to hear from our good group of mechanics/techs on this - if you take a high mileage motor with more clearances and running low pressure (but not consuming excessive oil), does one of these high pressure pumps increase your motor's life? Any cons to their use??

Dsg2500

This is the guide I plan on following for the motor.
http://www.ls1howto.com/index.php?article=4

What I'm looking for now is a van specific guide on how to get everything out of the way of the motor. Going to check out chiltonlibrary now.

Summitracing lists the Melling M295HV as
Oil Pump Volume:High-volume
Oil Pump Pressure:Standard-pressure
High-Pressure Oil Pump Spring Included:No

Guessing the Ultra Power M295HV is the same. Standard pressure, high volume. Still leaning towards the Ultra Power because of it's $55 price tag, versus $111 for the Melling, and I think I'm going to skip the timing chain, unless someone can convince me otherwise?

oldchevy

Putting in a high volume oil pump on a worn engine is also a band aid since it is not correcting the original problem. The bearings would still be worn. You would probably still have to go with a higher viscosity oil.

Dsg2500

hmm seems my post won't show cause I linked to youtube video. let me try again without the link. There's a video on youtube calledChevy Express Low Oil Pressure


Part of the top comment reads like this

So I think the pump could be the source of the problem. Especially if the van has a lot of idle hours with the AC on as I suspect. That use case would see a lot more heat than van that mostly runs the highway. Not a lot of room in the engine bay on these vans so it would seem natural for them to run hotter than trucks or cars.