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Old 08-31-2008, 10:10 PM
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Chevy .65L Duramax Diesel Problem

Looking for anyone with knowledge on the Chevy 6.5L Duramax Diesel. I have a 2004 2500hd that I bought used last December. It only had like 50,000 miles on it when I bought it. When I hit 55,000 miles - I changed the oil. After I did this, I noticed that my oil pressure gauge started to act like a tachometer. When my RPM's went down, so did the oil pressure gauge. When the RPM's went up, so did the oil pressure gauge.
I spoke with my mechanic, who is not a specialist in diesels. The problem is that there are no diesel mechanics in this area that I am aware of other than the dealer. We both agree that this is not correct, but cannot figure out why this is happening.
We have done the following things in troubleshooting:

1. Changed oil filter again.
2. Replaced the sending unit
3. Changed the oil to Delvic 15-40 (as we were told by the dealer that this is the specific brand used in chevy)
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Old 08-31-2008, 10:27 PM
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That's what should happen. The problem is you have an actual oil pressure gauge, as opposed to the "idiot light with a stick" like many new vehicles. Spin the engine faster, the oil pump goes faster. There is only a limited amount of space in the galleys and passages, so oil pressure increases. As long as you're carrying about 10 psi per thousand RPM, you're good to go.
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Old 08-31-2008, 10:28 PM
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What oil filter you use? Fram?

I have see that due gunk in passage get slow then sudden clog then oil pressure go raise little then try push finally it out. It happened on Ford 300 and Chevy 350 that never run hot enough most short drive for several years.

Do you see oil get dirty short time like sludge?
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Old 08-31-2008, 10:36 PM
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Quote:
Originally Posted by IA_James View Post
That's what should happen. The problem is you have an actual oil pressure gauge, as opposed to the "idiot light with a stick" like many new vehicles. Spin the engine faster, the oil pump goes faster. There is only a limited amount of space in the galleys and passages, so oil pressure increases. As long as you're carrying about 10 psi per thousand RPM, you're good to go.

There is a pretty good fluctuation in the oil pressure gauge. I am not questioing you, just trying to explain what is going on. I am trying to avoid the damn dealer because I know that will cost a fortune. The thing that concerns me is that it did not do this before I changed the oil.

Quote:
Originally Posted by Milwaukee View Post
What oil filter you use? Fram?

I have see that due gunk in passage get slow then sudden clog then oil pressure go raise little then try push finally it out. It happened on Ford 300 and Chevy 350 that never run hot enough most short drive for several years.

Do you see oil get dirty short time like sludge?
I use Wix filters. No, the oil does not seem to be producing sludge. I change every 5000 miles. Was using Rotella oil before the mechanic switched brands.
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Old 08-31-2008, 10:52 PM
Milwaukee Milwaukee is offline
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You mean when you stop at light engine idle at 650 rpm so oil pressure go down like middle when you touch pedal to go did oil pressure go high?

My 79 F150 alway do that if I stop it 15 psi at 600 rpm but go to 45 mph at 1,850 rpm oil pressure is 35 to 40 psi. it been do that when I switch to 15w40 diesel oil since 5w30 oil make worst it get 0 to 5 psi during hot run. Keep mind it have 327,100 miles now it still use everyday but not now we are still work on fuel system.
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Old 08-31-2008, 11:04 PM
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That's odd that it wasn't doing it before. Honestly though, if it was my truck, as long as I had over 10 psi per thousand RPM, I wouldn't sweat it. What are the hi/lo readings on your gauge? What does it seem to operate at most of the time?
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Old 08-31-2008, 11:37 PM
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FIRESCOOBY FIRESCOOBY is offline
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Quote:
Originally Posted by StriperPro View Post
Looking for anyone with knowledge on the Chevy 6.5L Duramax Diesel. I have a 2004 2500hd that I bought used last December. It only had like 50,000 miles on it when I bought it. When I hit 55,000 miles - I changed the oil. After I did this, I noticed that my oil pressure gauge started to act like a tachometer. When my RPM's went down, so did the oil pressure gauge. When the RPM's went up, so did the oil pressure gauge.
I spoke with my mechanic, who is not a specialist in diesels. The problem is that there are no diesel mechanics in this area that I am aware of other than the dealer. We both agree that this is not correct, but cannot figure out why this is happening.
We have done the following things in troubleshooting:

1. Changed oil filter again.
2. Replaced the sending unit
3. Changed the oil to Delvic 15-40 (as we were told by the dealer that this is the specific brand used in chevy)
First, the motor you have is a 6.6 Duramax, the 6.5 was the former GM Diesel.

Secondly, my Duramax (as well as every other vehicle) does that. The oil pressure will be fairly high first thing in the morning. After that the oil pressure will fluctuate with RPM's (engine load).
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Old 09-01-2008, 12:01 AM
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Quote:
Originally Posted by FIRESCOOBY View Post
First, the motor you have is a 6.6 Duramax, the 6.5 was the former GM Diesel.

Secondly, my Duramax (as well as every other vehicle) does that. The oil pressure will be fairly high first thing in the morning. After that the oil pressure will fluctuate with RPM's (engine load).
Exactly...You need to pay more attention on your trucks!
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Old 09-01-2008, 12:32 AM
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your 6.6! Duramax is normal. Nothing wrong with it there.
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Old 09-01-2008, 11:09 PM
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Quote:
Originally Posted by 02DURAMAX View Post
Exactly...You need to pay more attention on your trucks!
Sorry, our 2000 Chevy Diesel is a 6.5L, got them mixed up. The 2004 is a 6.6L.
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