Weird Oil Pressure Readings
#1
Registered User
Thread Starter
Weird Oil Pressure Readings
On my 96 12v, with 198K, I have gotten some weird oil pressure readings lately.
Short version: Oil pressure at 2000 RPM drops to 20PSI but come back up to 40 PSI at idle. After shutdown to check oil, the pressure stayed up at 40 for the rest of the trip.
Long version:
Usually it sits dead on 40 PSI, but as I was cruising up I-85 last night, at about 1950 RPMs, the oil pressure started to drop, slowly, and seemed to be around 30 psi. I turned off the cruise control and as the engine RPM dropped the oil pressure went back up to 40 psi.
I started the cruise back up again and it stayed just below 40 psi for a while. A few miles later it has dropped to the bottom of the "normal" range, I assume 20 psi. I then backed off the cruise control and got the RPM down to about 1700 and the pressure came back up to about 25 psi.
Once the oil presure dropped again to the bottom of the "normal" range, I pulled off at a rest stop to check it out.
Sitting in Park, I revved to 2000 RPMs and the pressure dropped down to the bottom of the "normal" area. I checked the oil and it was just below the Safe line (it was in the middle of the Safe area before I started this trip). Sure, I'm low on oil, but I can't believe that that engine could keep 10 quarts suspended in other parts of the engine anyway.
I also took out my "winter front", a plastic radiator cover that goes between the intercooler and the rediator. I fired it back up and all the rest of the way home, at 2000 RPMs, the oil pressure stayed at 39-40 PSI. I have not added any oil yet, pending asking you guys about what may be wrong.
Engine never sounded any different at any time. It's been purring (rattling?) like the wonderful 12v it is.
The only time I have ever seen oil pressure drop like that is when the oil return holes were clogged in the head of the engine, mostly Chebby 2.8L, when all the oil was pumped into the valve cover and could not drain back quickly enough to maintain oil pressure at higher RPM.
Am I looking at a potentially serious problem or a sender going haywire?
Any tips for further troubleshooting?
Thanks,
Chris
Short version: Oil pressure at 2000 RPM drops to 20PSI but come back up to 40 PSI at idle. After shutdown to check oil, the pressure stayed up at 40 for the rest of the trip.
Long version:
Usually it sits dead on 40 PSI, but as I was cruising up I-85 last night, at about 1950 RPMs, the oil pressure started to drop, slowly, and seemed to be around 30 psi. I turned off the cruise control and as the engine RPM dropped the oil pressure went back up to 40 psi.
I started the cruise back up again and it stayed just below 40 psi for a while. A few miles later it has dropped to the bottom of the "normal" range, I assume 20 psi. I then backed off the cruise control and got the RPM down to about 1700 and the pressure came back up to about 25 psi.
Once the oil presure dropped again to the bottom of the "normal" range, I pulled off at a rest stop to check it out.
Sitting in Park, I revved to 2000 RPMs and the pressure dropped down to the bottom of the "normal" area. I checked the oil and it was just below the Safe line (it was in the middle of the Safe area before I started this trip). Sure, I'm low on oil, but I can't believe that that engine could keep 10 quarts suspended in other parts of the engine anyway.
I also took out my "winter front", a plastic radiator cover that goes between the intercooler and the rediator. I fired it back up and all the rest of the way home, at 2000 RPMs, the oil pressure stayed at 39-40 PSI. I have not added any oil yet, pending asking you guys about what may be wrong.
Engine never sounded any different at any time. It's been purring (rattling?) like the wonderful 12v it is.
The only time I have ever seen oil pressure drop like that is when the oil return holes were clogged in the head of the engine, mostly Chebby 2.8L, when all the oil was pumped into the valve cover and could not drain back quickly enough to maintain oil pressure at higher RPM.
Am I looking at a potentially serious problem or a sender going haywire?
Any tips for further troubleshooting?
Thanks,
Chris
#2
Registered User
I would start by replacing the sender or hooking up a mechanical gauge to the port on the oil filter housing to verify if oil pressure is really swinging around.
#3
Registered User
Thread Starter
Haven't had a chance to check any oil pressure with a separate gauge yet, but here is a pic of what I saw as I rode down the highway. Quite unnerving. But turn off the cruise control and the pressure goes back to 40 as the RPMs go down.
Chris
Chris
#4
Registered User
Thread Starter
Mechanical gauge installed, in the port beside the turbo oil line, over the filter.
Cold idle 80 psi.
Warm idle 28 psi.
Warm 2000 RPM, 65 psi.
The electrical gauge stays right around 40 psi ALL the time. Since I have had the mechanical gauge connected the electrical gauge has not dropped down the the level as pictured above.
I understand that there is a plunger or something in the oil filter housing that may limit the oil pressure because of build up in the regulator passge, but in this case I have great fuel pressure but a gauge that reads wrong, sometimes worse than others.
Do I need a sending unit?
Thanks,
Chris
Cold idle 80 psi.
Warm idle 28 psi.
Warm 2000 RPM, 65 psi.
The electrical gauge stays right around 40 psi ALL the time. Since I have had the mechanical gauge connected the electrical gauge has not dropped down the the level as pictured above.
I understand that there is a plunger or something in the oil filter housing that may limit the oil pressure because of build up in the regulator passge, but in this case I have great fuel pressure but a gauge that reads wrong, sometimes worse than others.
Do I need a sending unit?
Thanks,
Chris
#5
Mine did that and it was a bad sender. Mine was actually leaking a small amount of oil and when the mechanic removed it the thing fell apart. That would've made a nice streak on the highway if it had let go on the road. Now back to normal pressure. Just like the owners manual shows, slightly above 40psi. most of the time.
#6
Spend $30
Mine did about the same thing a few weeks ago. $30 +/- for a new unit, and viola! We be back on the road with a pressure reading that is steady as a rock, more or less.
I'm learning that just about everything for this truck costs $30. Thermostat, $30; fuel filter, $30; Oil unit, $30.... Yeah, I know, I have priced a few of the other baubles that are several times $30.
I'm learning that just about everything for this truck costs $30. Thermostat, $30; fuel filter, $30; Oil unit, $30.... Yeah, I know, I have priced a few of the other baubles that are several times $30.
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