So I just bought an 03 gmc 2500HD with 126000 miles. I have come to find out that it has low oil pressure. A friend of mine has a scanner that he was able to hook to the truck while it was running and verified that the oil pressure was low, like 8-9 psi while idling but runs at 30-40 while driving at around 1500rpm. I haven't hooked a mechanical gauge to it yet. When the truck is cold the gauge reads 60-70 psi. When the motor and the oil are up to temp, it reads low pressure. I am hoping that this is a lazy sending unit but I thought I would ask here first. My process of thinking is that when the sending unit warms up, it starts reading low. If it is not the sending unit, I guess the next step is to hook a mechanical gauge to it and possibly change the oil pump. I hate to think that I had to change the oil pump at 126k. Any opinions?
Low oil pressure from factory gauge
- Thread starter JBabb
- Start date
You need to hook mechanical gauge up first to verify. You shouldn't do anything else until you do that first.
So if I hook a mechanical gauge up next and it still reads low, then the motor comes out to replace the oil pump, correct? Can you recommend a mech. gauge to get to hook up? I am thinking of doing gauges on the pillar anyway so I may just get a good gauge and reuse it later on the a-pillar, but, if I could get a cheaper one just to test with for now that would be good too.
Ok so I hooked up a mech. gauge and got about the same readings. Low (7-9psi) at idle, about 30-40 while driving at around 1500rpm. I have now eliminated all electrical stuff and know that the motor has low psi. Now what? The truck only has 126000 miles on it. I can tell the oil pan has been off before so I know something is up with this thing. If it has been run hard in it's past life, could the bearings be worn and that is the reason for low psi? If so I am talking rebuild right? How much money are we talking for a stock rebuilt Duramax? I am kind of starting to wish I had never bought the truck...
Why do you think the oil pan has been off before?
And installing a new oil pump is no guarantee on fixing. Could be leaking anywhere internal. I would also change the oil filter to a ac delco.. You can check oil pressure at the filter and on a ballet plug, if you look at the oil flow possibly tell where its bleeding off at
And installing a new oil pump is no guarantee on fixing. Could be leaking anywhere internal. I would also change the oil filter to a ac delco.. You can check oil pressure at the filter and on a ballet plug, if you look at the oil flow possibly tell where its bleeding off at
It could be, I am learning too. I know a good deal about gas engines but little about diesels. From what I know, idle at 7-9psi and flashing low oil pressure on the message screen isn't good, but I could be wrong. My fathers idles at 35 or so and runs at 50-60 but his is an 05.
Every duramax iv had is 20-25psi at idle.
Gm uses grey silicone called GMS on the upper and lower oil pan so I'm sure it's factory.
Gm uses grey silicone called GMS on the upper and lower oil pan so I'm sure it's factory.
Ok so take the oil pan theory out, the silicone is grey. I have found a wiring harness in the truck for a edge products tuner and by matching the shape of the plug, it looks to be an edge with attitude package. Could running this tuner at a high setting have run the motor too hard and caused excessive bearing wear? I am just thinking out loud here and as mentioned, I know little about diesel engines.
Now I am starting to wonder about bearings, main and rod. Could this be where my oil pressure is being lost possibly? I have also been reading about the nut on the oil pump drive gear coming loose. Would this be worth checking? If I understand it right I can take the front cover off without pulling the motor to check the nut but if the pump has to be changed the motor has to be pulled. Also have read alot about relief valves sticking. I have read so much it is all running together.
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Other than checking your oil temps to see if it's being thinned out due to a oil cooler problem, you'll be tearing it down.