What is an acceptable oil pressure??

[steved]

I have finally gotten around to putting a "real" guage on the truck... when hot, I'm getting 60psi at anything above idle and around 20psi at idle... this is with a bypass filter. When it was cold (70*), I was getting 75psi all the time...



Now, I'm pulling my pressure from the 1/4" supply line going to the bypass filter... about 12 inches from the supply connection...



Is 20psi at an idle acceptable and safe?? I plan on reducing the orifice in the bypass soon... but not that much...





steved

 

[jyoung13]

Steved

I put in a mechanical oil pressure guage a couple of weeks ago. Tapped 1/8" NPT port in top of oil cooler/filter housing,ran #4 braided line (over kill ,but already had) to firewall,#4 AN bulkhead thru firewall then tubing that came with guage up to guage. I have the same readings you discribed,I,d say your fine,and yes 20 PSI at warm idle is safe.

Jeff

 

[Vaughn MacKenzie]

Steve you'd probably get better readings closer to the engine. . . the further away the lower the pressure. When I had a gauge on my '01 I pulled out one of the oil gallery plugs on the driver side of the engine block. I had to get a metric adapter but it worked great. I don't recall my readings (traded the truck long ago) but they were higher than 20 at idle. Seems 35ish was more like it. I don't know if the 3rd Gens have the oil gallery plugs on the block like the 24v but they're not very big and screw out with an allen wrench as I recall. I think they tap into the oil supply to the camshaft since the cam is on that side of the block.



I found this old thread, see my post (Post #5) https://www.turbodieselregister.com/forums/showthread.php?t=45047



Vaughn

 

[nickleinonen]

i've got 18-20psi idling hot with 0w40 synthetic in the sump on a mechanical gauge taken off the lube oil gallery on the left side of the block. anything over 15psi idling hot is a safe number off the left side of the engine. [i lost about 2psi going from the filter pad to the engine left side]

 

[elandon1201]

I have gotten as low as 17psi at warm idle through the juice attitude. Not a mechanical gauge though. a friend of mine who works on big rig cummins says 10 psi per 1000 rpms is more than safe.

 

[steved]

I'm running an electrical guage, not a mechanical... and it is between 20 and 25 psi... seems to stay above 20psi...



I'm going to reduce the size of the bypass filter orifice to up the pressure some... I had to up the size since I had broke my drill bit...



Just worried that I might be a little too low...



steved

 

[Vaughn MacKenzie]

It could be the oil pressure on my '01 was around 20 at idle, just not remembering since it's been quite awhile.

 

[MMeier]

Steve you'd probably get better readings closer to the engine. . . the further away the lower the pressure.



Vaughn

How is that Vaughn? I always thought pressure remains constant as long as the end of whatever you are hooked up to reamins closed off? Not knocking you or anything, just i do not think he would get a different reading hooking up closer to the engine, anyone else?

 

[Vaughn MacKenzie]

The "end" isn't closed off because he's tapped into the supply line to his bypass filter, so oil cirulates through that and back to his oil sump. As a fluid runs through a passage, pressure drops more and more the further along you go. The faster the fluid runs or the greater the distance, the greater the drop. Cap off the end and pressure is the same the full distance.



Vaughn

 

[MMeier]

Gotcha, my mistake !!

 

[steved]

The "end" isn't closed off because he's tapped into the supply line to his bypass filter, so oil cirulates through that and back to his oil sump. As a fluid runs through a passage, pressure drops more and more the further along you go. The faster the fluid runs or the greater the distance, the greater the drop. Cap off the end and pressure is the same the full distance.



Vaughn

Exactly... I figured it might read a tad low since it is located away from the source, in a small "restrictive" line, and in a supply line... but at the same note, the oil pressure taken off any part of the engine will be from a "supply line" too... not like the oil system is a single pass.



At least I'm seeing "normal" oil pressure at idle... I doubt restricting the bypass will actually increase the pressure physically, but might increase the guage reading some... the main thin with restricting the bypass more is that I think it's flowing WAY too much oil now...



Thanks for all the feedback... for the moment, it seems I have nothing to worry about...



steved

 

[Kirwin]

Engine oil pressure

Cummins min spec is 10 PSI at idle. Dodge's "gage" alarms at 6 PSI. These are my observations using a Cyberdyne digital gage that's tapped into the oil rail at the fitting for the old style vacuum pump oil supply line on the driver's side of the block, (just forward of the factory oil pressure sending unit) when pulling off the interstate with hot oil, oil pressure will drop below 6 psi :--) momentarily. In order for his to occur the engine must have been pulling and the coolant must be hot (>205 F) this occurs when I stop at a rest area just off the interstate after the truck has been pulling (IE hot oil) As temperature falls the oil pressure rises back up to 14-17 psi. This happens on days with ambient temperatures >90 F. I'm not sure about what everyone else sees but I posted this a while back and most of the people who replied had their gages plumbed into the oil filter plug which I believe is upstream of the filter. I don't know how much the pressure drop across the filter is, but it must be some. Also my engine is an early 03 HO engine with the constant under piston spray J nozzles, its possible that Cummins upgraded the oil pump due to this additional constant drain on the oil supply. I'm close to 35,000 miles 90% pulling and so far no issues. It does make me nervous though.

On my 97 I see about 19 PSI minimum using the same gage set up although not the exact same gage and sending unit. I'm not sure what the accuracy of the Cyberdyne gage is at such low pressure but they seem to be consistent between my 3 diesels.

 

[steved]

Mine seems to stay around 22psi regardless of whether it is "hot" or just at operating temps... and unlike other posts, I have read about the 115psi pressure and I'm nowhere near that either... mine has not broken 75psi... seems to settle in at about 60psi cruising... and I have not seen anything less than 22psi... even after running very hard (WOT) and comoing to a complete idle... drops to 22psi and that's it.



I am under the impression that the ports on top of the filter are post filter (they hopefully wouldn't feed unfiltered oil to the turbo... my logic anyway)...



I would be nervous too if my oil was dropping like that... but as another point... you might be near "the end" of the oil's passing through the system (like at the point is is ready to enter the crankcase to start the cycle over again) and might not see much pressure... would be like me installing the sending unit downstream of my bypass (I'm not, but to give you the idea)...



steved

 

[JStieger]

Normal driving ~20 psi at idle on a mechanical gauge off the oil filter head directly plumbed into the cab.



Hot-rodding ~18 psi at idle and then it comes back up to 20 psi when the engine cools down a bit.



Cold start ~90-95 psi at ~2000 rpm.



Normal hot cruise ~60-65 psi.

 

[steved]

Well, at least I'm within the norm range of pressures!



I might go full mechanical later on... looking at a mechanical fuel guage right now...



steved