mac_in_mt

I am a newbie and have come to this site for a problem I am experiencing and am looking for the most logical approach. I have read many other similar posts but haven't quite determined my approach yet.

I have a 1996 Chevey K1500 with the Vortec V8. About 2 years ago I had the oil changed just before a big trip (usually change oil myself but ran out of time). By mid trip I was experiencing low oil pressure at idle with a warm engine. When I returned home I changed the oil and the problem went away, for a while. The low oil pressure has slowly been getting worse. I finally took the truck into a shop last week and a manual oil pressure gage confirmed 3 pounds of pressure at idle. An oil change and two bottles of STP did not improve the pressure. I have also been experiencing an occassional misfire (by the computer code) although the mechanic did not indicate if it was random or consistently on the same cylinder. Neither the mechanic or I could hear any unusual sounds (knocking, pinging, etc) from the engine at idle, even if left to idle for 10 or more minutes. And finally, I have rarely but occassionaly smelled a slight antifreeze odor from the vehicle. I have not seen any signs of oil in the antifreeze and the mechanic pressure tested the antifreeze with not indications of a leak.

I have consitently use Mobil 1 10W30 and Fram oil filters. Things I am wondering about:

1. I have considered changing to a heavier oil and/or to a high volume oil pump however I am afraid that I would be just masking the real problem, whatever that may be.

2. Does this motor have a pressure release valve near for the oil filter that might be stuck open, thus bypassing the filter and not providing back pressure?

3. What does the misfire indicate. I have seen other posts that this could indicate a rod or valve issue but that is normally accompanied by a kncocking sound. The misfires are fairly rare and the service engine light is only on every now and then.

4. The mechanic told me to baby the truck and see if anything gets worse, but I would like to find and fix the issue before I am having the engine rebuilt.


Thanks for your help!

oldchevy

With 3 pounds of oil pressure at idle, I would be afraid to drive the truck. I would be afraid of ruining the engine. This is something that needs to be looked at now and repaired now before the engine is completely fried!

MDTAHOE

Usually low oil pressure is caused by a worn out engine not by the oil pump. As bearing clearances get larger pressure goes down. How many miles on it? Putting thicker oil in it is just masking the problem pressure will go up but volume goes down. Think of it like putting your thumb over the end of the garden hose, the water goes further but laess comes out.

mac_in_mt

The truck has 110,000 miles. The oil pressure issue started at about 100,000 miles and it occurred immediately after the oil change which I did not perform....conincidence?

So why are my bearing clearances suddenly getting larger and how do I troubleshoot or fix the cause?

Will the clearances continue to get larger with a high volume pump or thicker oil?

Do I fix the bearings now, or baby the truck?

Thanks!

EinST

That's not many miles on synthetic oil. Maybe the oil pressure relief valve (integrated into the oil pump) is malfunctioning. The mechanic should've mentioned the possibility.

mac_in_mt

I finally saved some money and had a new high volume oil pump installed. Little did I know that the mechanic could have but didn't check bearing clearances while he had the oil pump out. After the new oil pump I am still experiencing very low oil pressures. I have never seen any metal in the oil. I have since put the truck up for sale and a perspective buyer had the truck checked out at a different shop. They apparently did some test that indicate the new oil pump is hardly pumping any oil.....????? Would they have been able to test this or are they just checking the oil pressure manually?
Any suggestions on what I should do next? I am beginning to face a rebuild aren't I?

Thanks

Raymond Wood

if you have a fram filter, change it to a wix or delco, I had the same problem, changed filters and now back to 20psi at idle, the fram filter collapsed on the inside, and oil wasn't circulating right, my 5.7 has 192xxx on it and with a Delco filter has great pressure.

Clarence Kalili

try cleaning out the screen behind the oil sending unit. You have to remove the sending unit first. There's a screen back there. You can use some carb cleaner and compressed air.

Kdmedic

×× my 96 k1590 broke down for 7" years and oil turned to thickish oatmeal.
Flushed with engine flush and 15w40 2x even turned it over with NO filter to expel ry Went to an oil pan heater for winter and used Maxima V Twin straight 70 wt oil.with KN HP2001 filt.

Reading pressire on pillar was 20psi when engine was at 5 psi at operating temp on dash.
Installed Glow 2" gauges oil pressure and temp on filter adapter, , with 3 on A pillar one on dash.
Pressure difference caused me to pull a leaking oil pressure switch bedind distibutor.(relaced 2x)
×× my 96 k1590 broke down for 7" years and oil turned to thickish oatmeal.
Flushed with engine flush and 15w40 2x even turned it over with NO filter to expel ry Went to an oil pan heater for winter and used Maxima V Twin straight 70 wt oil.with KN HP2001 filt.

Reading pressire on pillar was 20psi when engine was at 5 psi at operating temp on dash.
Installed Glow 2" gauges oil pressure and temp on filter adapter, , with 3 on A pillar one on dash.
Pressure difference caused me to pull a leaking oil pressure switch bedind distibutor.(relaced 2x)
70wt oil temp 220° f, coolant 189° to 198° pillar 66psi to 42 psi, oem 42° to 4T30PSI
On 70wt 2months 3- 4/2022. dumped (saved). 15w40 Delo C/C S/N spec.
perssures pillar 66 to 38, oem 42 - 20.
Tomorrow changi(ng oil to Castroi high milage 20w 50 and last KN HP2001 from 70wt .
Will change to 50wt if i must.
will change oil pump in summer to high volume. Then change engine.
was 2nd owner since 1999
Has 157, 000 mi. New England never hot rodded.
Trans blew at 104,000mi
​​​​​​​Kevin Dixon