I am having an issue with my truck once it is fully warmed up. When it is cold it sounds perfectly normal but once it is fully warm and I am in gear I am getting a knocking sound under the hood. My oil pressure seems kind of low with the 195 thermostat in it so I threw my 180 stat in to see if it made a difference. It brought my OP up quite a bit but the sound is still there. I changed my oil even though it was supposedly changed less than 1000 miles ago. The truck runs great but I have noticed that from the first time I drove it that when you first hit the accelerator taking off from a stop that there is a "dieseling" sound for a split second. YES I KNOW MY TRUCK IS A DIESEL!!

Anyways, I wonder if the two items are related and if it may be an injector that is malfunctioning. The truck does not blow any smoke at all and it still does it even without any of the mods in my signature. I've read that a CP3 that is not properly timed with the engine can cause this issue. Anyone else here heard of this.

Looks like a dealer visit is imminent but I like to be able to tell them how to fix my stuff so I don't get the "Could not duplicate issue" response.....

 

More specific info , you mention oil pressure , but give no number ?
I can hardly believe that changing the thermostat is going to affect the oil pressure very little , most temp / pressure varying is at cold to operating temps , not 15* difference in operating temp .
I wandered if you have had the truck for long , not knowing for sure if oil was changed & saying you noticed since 1st time you drove it ?
You could have fuel issues making the noise , cracking the injector's lose , one at a time to see which one may make the noise go away .
Be careful doing that , the high pressure can cut through you if you get everything just wrong while cracking injectors .
Unless you have a good dealer , or are under warrante , I would not go to a dealer , for anything , just seems to be the way things are , see if someone in the area or this site knows a good shop in your area .

 

No...........do not crack an injection line loose on a common rail !!! It is unsafe and will not acomplish anything. The injectors can be shut down electronicly

 

Low oil pressure means that it is just barely above the minimum normal line on the guage. Changing to the 180 stat made the oil guage needle move to the right almost 1/4". That's a pretty big difference.....

I bought this specific truck because it still has a full warranty. I may as well use it....

 

Doesn't the CP3 just build pressure for the common rail ? The injectors are fired electronically.............I could see a VP44 or a 12V pump requiring a specified timing.

Greg

 

Well, first off, I could swear I put this in the 03-07 3rd gen section!!! Did a mod move this here???????

There is a thread at another Cummins site where guys are having my exact issue and are solving it but somehow realigning the gears on the CP3 so that there is a 30 degree difference from the spot they were previously and this is fixing their issues. I have never even inspected a CP3 in all my years so I really don't want to start pulling it apart and experimenting. Greg, it has something to do with the CP3 gearlash while the truck idles. As soon as I start going it goes away. The truck still runs fine too...

I think I will see if I can have the diesel tech at the local dealer hear the problem while it's happening and see what he thinks. Hopefully I can do this instead of having to go through the hassles of a dealership appointment....

 

I just moved it to the 03-07 section for you.

 

Isn't the oil pressure guage on these trucks really an idiot guage..? I think it moves to the right if over ?? a certain pressure? I know the guage shows a range but did not think the sensor and guage are capable of showing specific pressures.

 

'Zilla,
I'm experiencing the same sound on take off occassionally, then it goes away. I'd be interested in what you learn about this. I don't have any warranty. Could you let me know please? Thanks.
Andy

 

Thanks for moving this T-Rad...


Eat Beef, I'll be sure to post my findings...

 

Sounds like a little air in the lines when you first start it up or carboned up injectors. Hook to a heavy load and work the dog out of it. This clears mine up everytime. Work that truck.....

 

Well, I'm trying to determine if I just got spoiled having the 08 6.7 truck which was ridiculously quiet and now when I hear my regular diesel engine that makes more noise I start worrying about noises that are really nothing...

 

Here you go boys!

http://www.cumminsforum.com/forum/3r...g-results.html

Someone should turn this into a sticky or FAQ

 

Like I said, Go work it hard and clean it out. No need to mess with the CP3.

 

Well, since your post, Spooler, I have driven the truck a bit harder than I had been. I have noticed two things now. My mileage actually went up slightly by doing this and the last two times I have driven it the noise was not there. The first couple days it almost seemed to be getting louder but the last couple days when it was knocking it was getting more faint. I don't drive it everyday since I have an awesome 2000 Ford Taurus to drive as a commuter car so it may take a few days but I'll post back if it starts knocking again...