Brand new truck with the LLY/Allison combo. I noticed that the oil pressure gauge moves with my RPM. If the RPMs are climbing the oil pressure gauge gets up to about half way. When I let off the throttle, the pressure falls. Not to redline, but around 1/4 of the range. While theoretically this would make sense, I have never seen an oil pressure gauge do this. I know my old Ford used to have one pressure at any RPM. Is this normal?

It is normal. My truck does the same thing.


I heard the reason they did it was to stop the "Tick" that people would hear on the LB7 motors at Idle.


When you Cold start it, Pressure stays high until the engine is up to operating temp.

Funny mine moved that much too I just figured more demand more pressure. Glad to see it is normal was not to worried about it, I was just going to check it at the dealer next time in.





TC

Same here but only when the engine is warmed up.

TEXmudder - the Fords gage will stay in one place because it is hooked to a switch same as a idiot light! Must change the sender if you want to see the actual pressure. Often wondered why mine never changed and then read a Q&A in popular mechanics that told after a certain model year they went to switches insead of a "resister" sender! To save a nickel????

Mine, LB7, at normal operating temp will vary from 30 Psi to 80 and any where in between ,depending on throttle position from W/O to closed ...





Mac http://www.dieselplace.com/forum/smileys/Geek.gif

My LLY ticks every now and then. I really noticed it right after I did my first oil change.

Guy's Oil pressure is directly related to engine RPM.


The slower the lower the faster the higher.http://www.dieselplace.com/forum/smileys/Clap.gif


When oil is cold it is also thicker and won't flow as easily threw the bearings and will create a higher pressure.


As long as you have about 2 psi for every 100 rpm at idle that's usually considered good.http://www.dieselplace.com/forum/smileys/Approve.gif


And depending how loose or tight the bearing tolerances are set will determine higher oil pressure readings. Plus the oil pump to a extent.


Remember it's not the actual number that's important because each truck engine, oil pump, oil pressure sending unit, and finally oil pressure guage are a little different, as long as the oil pressure stays there from now on or close to it is what's important.


And naturally as the engine get's more miles and is worn the bearing tolerances will increase and the pressure will go down some.


If you put a mecanical oil pressure guage you will see the pressure move up and down quicker than what the electric guages show.


And trying to compare the Duramax and GM to the Powerpuke and Furd is a big mistake.http://www.dieselplace.com/forum/smileys/Big Smile.gif


My .02 Diesel Dragonhttp://www.dieselplace.com/forum/smileys/Cool.gif

Well its the only diesel I can compare to as the PowerJoke was the only other one I have owned. At least the Duramax isnt leaking oil on my driveway like my PSD did.

My LLY ticks every now and then. I really noticed it right after I did my first oil change.


What oil did you use? Mine seems much quieter since my oil change.

My LLY ticks every now and then. I really noticed it right after I did my first oil change.


What oil did you use? Mine seems much quieter since my oil change.





Delvac 1300, I figured I would change to synthetic at around 10K.

Just had the dealer change the engine oil/filter & noticed my oil pressure seemed to be about 15 psi greater now than when I took delivery/first 1000 miles. Had been seeing about 45-48 psi cruising at 1950 RPM fully warmed up. Now I am seeing the 60 psi range even below 1800 RPM (again - all warmed up). Seems to be higher pressure across the RPM range. Not sure what spec oil came out but 5W40 appears to be want went in this time.


Any thoughts? Is this normal? Is this a problem? Just a little paranoid about our brand new hauler. Thanks, Tom B

I know this isn't about a diesel but should help with pressure worries.... Chevy built a small block with max allowable clearances and (I think) 5w-30 oil.... at 600 rpm idle pressure was about 4 psi with no apparent damage to engine.. believe I saw this in an old GM TSB .... late 80's early 90's release, that or in the Chevy News mag they used to send out to dealers once a month... hope this helps. In 24 yrs of being a tech I don't believe I've seen any chevy engine with oiling system problems.... neglect for sure, but not prob with basic oil system, Stock engines only as I know for max performance you may need some oil system mods.

Oil preasure is directly realted to engine clearence , volume of the oil pump and oil viscosity. The more mileage on an engine the more clearance. The more clearance the less preasure. The heavier the viscosity the more preasure (thicker oil). The more volume the higher the preasure.(More oil has to go through a fixed space thus building preasure. If you have an engine without wear and the right viscosity oil in it don't worry about preasure. As long as the oil is circulating you are ok. The faster the engine turns the more the oil pump pumps oil thus increasing preasure. The bottom line is don't worry about it. Diffrent oils can run diffrent oil preasures. If you run the same preasure day in and day out and suddenly see a dramatic decrease in preasure You should have it checked otherwise drive and enjoy!