Low oil Pressure w/ new pump

[Blzr6.2'83]

I have oil pressure that is 10 at warm idle and 35 at any speed from 60 up. This is the second new pump I have installed in like 2 years and I have had the same results. I need to replace the rearmain seal and oil pan gasket because it is leaking like crazy( I guess I didn't take enough time cleaning it and sealin it last time :( ), so I will be down there again :mad: . Should I install one of the heavy duty oil pumps from the 98+ engines while I am replacing the gasket or leave it like it is? Will it make a differnce if I do?
Thanks,
Kyle

[Blzr6.2'83]

Oh yeah, I have a mechanical guage that is almost brand new so I know it is right. I am guessing there is alot a bearing wear, it has 200,000 very hard and abusive miles.

[john8662]

How much time do you have before you need the truck running again?

I'd consider pulling the pan and checking a few things, The main thing to check will be to pull the #1 main bearing cap and check for wear on the bearing. Since you are there you will want to compare so take down the #4 main bearing cap as well. Then, compare the wear. The #1 main bearings will get less oil pressure than the rest of the system because they are on the end of the oil pressure circuit, so these bearings will show you the worst wear in the system. If you find severe wear or pitting (take pictures if you're unsure and post them) then new set of bearings for BOTH the rods and mains may be in order.

If you decide to take bearings out, take very very carefull notes to exactly where they came out. GM used different sized bearings on both rods and the mains. So if you need new bearings you will know exactly what bearing you will need.

If none of the bearings "look" bad, then it's time to take some plastigauge and check the clearance (pain in the rear from underneath).

Your suggestion of running the 98+ oil pump is a good one, and every engine that I get the pan off of will get the newer pump (either Melling or the OEM one) but the bigger pump none the less. I don't think it will matter if it's a 6.2 or a 6.5, the later pump is a better pump In my opinion.

The downside to this is that if you get the new oil pump installed and still have oil pressure issues, you will then know what the problem is.

What grade of oil are you running?

Another thing that it could be is you could have a rounding hex rod that drives the oil pump. Take the time to inspect this rod thourally, it could be rounding and not driving the oil pump fully.

[Blzr6.2'83]

I run Rotella T 15W40. Is it possible to change the bearings from underneath or does that require a whole rebuild? This is my only car and I drive it to work and shool six days a week so I only have from saturday at noon until, sunday night to fix it. SO how long will all that take? I am guessing it would be a two weekend job or during christmas. Where do I use the feeler gauge to check the wear? I did a search and saw one that said if you use the new pump on an old engine that it stresses the oil pump drive rod and that it could break on cold starts, is this true?

[john8662]

The newer pump is a higher volume unit. I haven't heard of the rod breaking. But, like I said, the rods can round, but I haven't seen any in person. If it were me and the rod looked shiny on the end that goes in either the pump or the end of the vacuum pump, I'd replace it, I don't think it's very expensive (less than $10 for sure).

As far as measuring clearance, you use plastigauge. It's basically a strip of a waxy-platic material. To use you first remove the bearing cap leaving the bearing it in. Then place the strip of plastigauge onto the crankshaft surface, then reinstall the bearing and cap and torque to specs. After it's torqued, then remove the cap again and use the legend found on the package that you bought with the gauge. You'll then match how far the waxy-pastic material spreads out. The legend will tell you approximatly how many thousandths of an inch of clearance is in between the bearing and the crankshaft surface.

Anyways, you could do it in a weekend if you started early and worked late. It's going to be difficult to work on, although possible. The hardest part of the project is KEEPING DIRT OUT OF THE ENGINE! This is especially important on bearing surfaces, because the trapped dirt will score the crank and bearing.

I'd check the bearings themselves visually, and the crankshaft surface underneath the bearing/insert.

[rob1681]

hey firend,

this might sound stupid but i had the same problem with my 88 6.2L and it was the brand of oil filter i was using changed to wix and it runs great oil pressure.

[Ratau]

Could anyone tell me what is route off the oil through the engine? Oil pump, filter, cooler and so on and where is the dump valve located?

[NH2112]

Excessive cam bearing clearance is probably the most common cause of low oil pressure, on an otherwise good engine (strong pump, etc.)

[5.7L oldsdiesel]

I've read in some older service manuals that you can remove the oil pump and use compressed air with a rubber tiped blow gun and blow compressed air into the oil port from where the oil pump was bolted in place.With the air being blown through,you can look for the problematic area.If you see streams of oil coming down from the rods,then thats the likely cause for the low oil pressure because of excessive clearance.If you just see the oil dripping down slowly with a drip every 2-3 seconds,thats sort of tells you that section of the engine is probably okay.But like NH2112 stated,worn cam bearings will allow low oil pressure to occur if they are worn badly enough.

[Ratau]

I agree on what you say but that normally happens over a longer period. The oil pressure dropped after I change heads and oil filter. Maybe a blockage some ware. Does the oil go to the cooler before it goes to the engine?

[BobND]

Originally posted by 5.7L oldsdiesel:
I've read in some older service manuals that you can remove the oil pump and use compressed air with a rubber tiped blow gun and blow compressed air into the oil port from where the oil pump was bolted in place. An old racer's "cheapy" trick is to take a (new) pump-up garden sprayer, modify the nozzle fitting to accept a pipe thread fitting, and attach it to the oil sender port.

With the oil pan off, put clean engine oil in the garden sprayer, pump up the air pressure, and take note of where the big streams of oil coming out the lower end are from.

That modified sprayer can also be used to pre-lube an OH'd engine before startup, and will perfom as well as ready-made units costing several hundres dollars.

Some of the parts, though, may not be oil resistant over a long time, though, posibly making it a one-use unit. But for about $10.00, who cares, if it gets the job done!

[mhagie]

For what its worth my fresh DD reman runs 26/28 @ 65 mph 1900 rpm and 13/15 @ idle.
I don't like these pressurews worth a Dam but can't find a spring as yet to up the pressure.
Supposed to have the 98 up piston oiler pump in mine.
Mine seems to be very sensitive to oil temp as after a long highway run when returning to town oil pressure climbs a few pounds.
Merle

[Blzr6.2'83]

I put the newer oil pump on and the pressure is 20 psi higher at highway speed. I also found out that my main bearing are worn horribly so I am getting a block to rebuild. The new pumnp helps a lot, it also seems to be running smoother but that might just be my imagination.

[mhagie]

I believe that this winter i will pull pan and check out the pump I may not have what I think I have for a pump.
I haven't seen oil pressures this low since my old 53 chev 216 engine.
Merle