Oil pressure at idle

[Kirwin]

I have had a Cyberdyne digital oil pressure gage now on my 03 HO Ram for several months. I'd like to get the TDR's input on my observations of what I consider to be on the edge of too low oil pressure. My sender is mounted in the oil galley plug where the vacuum/power steering pump oil supply used to mount on the 2nd gen trucks. I used Premium Blue 15W-40 until the 15K oil change then I switched to Premium Blue Extreme 5W-40. After a run at freeway speeds, hauling my travel trailer (20K CVW), I pull in to a rest area, and at idle I have see oil pressure drop to 6-7 psig. It seems to slowly rise up to 10-12 psig over the next couple of minutes (as the oil cooler does its job?). On my 97 I have the same gage/sending unit set up and hot oil pressure runs 18-20 psig and does not seem to change at all at a rest area stop. Has anyone else with an 03 Ram seen this? Are the continuous oil jets that are used on the HO engines causing oil pressure to fall that much lower on the 03 HO Rams vice the older style with the piston cooling nozzles? I know Cummins specifies a minimum oil pressure of 10PSIG at idle but I am curious if this is just a transient situation and thus not really an issue. I have been using these Cyberdyne gages for several years and they seem to be very reliable and accurate. The Factory gage does NOT reflect true oil pressure either on the 03 or the 97. I have never got the "check gages" light so obviously if I were relying on the factory gage I wouldn't even know that there MIGHT be a problem. Sorry for the long post. Ken Irwin

 

[Vaughn MacKenzie]

Kirwin, I believe the oil supply you tapped into is low flow/volume and will not give you a good reading.



Either tap into the plug on the oil filter mount or on the driver's side of the block there are oil gallery plugs where the system feeds the cam & main bearings (at least on the 2nd gen 24-valve). I tapped into that on my last truck and typical oil pressures I saw was as low as 25psi when hot and as high as 90 when cold. Typical cruise was 40-50.



Vaughn

 

[rbattelle]

Originally posted by Vaughn MacKenzie

Kirwin, I believe the oil supply you tapped into is low flow/volume and will not give you a good reading.



Either tap into the plug on the oil filter mount or on the driver's side of the block there are oil gallery plugs where the system feeds the cam & main bearings (at least on the 2nd gen 24-valve). I tapped into that on my last truck and typical oil pressures I saw was as low as 25psi when hot and as high as 90 when cold. Typical cruise was 40-50.



Vaughn

I agree with Vaughn...

 

[Kirwin]

I have to disagree with you on this point as this is the same location that the factory uses on the engine to sense oil pressure. I reference page 9-340 in the 03 service manual and from the Cummins manual for option SD9009 for the 97 show that this location is after the oil filter but it is the oil pressure the is present at the main oil rail. This is also the oil supply for the P7100 pump in the 97. Now I'll agree that this oil pressure is probably lower that the oil pressure from the top of the filter head as this may be before the filter I don't know about that. But I don't think that this point is any different than any other on the mail oil rail.

 

[rbattelle]

Originally posted by Kirwin

I have to disagree with you on this point as this is the same location that the factory uses on the engine to sense oil pressure. I reference page 9-340 in the 03 service manual and from the Cummins manual for option SD9009 for the 97 show that this location is after the oil filter but it is the oil pressure the is present at the main oil rail. This is also the oil supply for the P7100 pump in the 97. Now I'll agree that this oil pressure is probably lower that the oil pressure from the top of the filter head as this may be before the filter I don't know about that. But I don't think that this point is any different than any other on the mail oil rail.

Which number in the diagram on 9-340 locates the point where you're taking the reading? Is it 10? If it is, that's the point where oil is returned to the sump and I would expect it to be of quite low pressure.



Anyway, the standard for checking oil pressure is at the filter housing, and that value is 10 psi at idle. As long as it's at least 10 psi there, then technically you should have nothing to worry about, even if the pressure is lower elsewhere. There is no published standard for pressure anywhere else on the engine. Plus, the factory switch is set to a minimum of 6 psi (below which the oil pressure "gauge" will peg at 0 and an oil light will illuminate).

 

[Kirwin]

Sender location

rbattelle, I just went and checked both trucks. The 97 oil pressure sender is teed into the OEM oil pressure sensor tap on the engine block. On the 03 the after market sender is tapped into the oil rail location about 3" forward. The best picture in the 03 manual that I can find is on page 14-58. The OEM oil pressure sender is identified as 17. If you look over the ECM there are two holes in the block that are just plugged off in the 03. I am tapped into the one right by the bracket IE the center one. Based on this location I think that this is the oil rail that feeds the entire engine. I understand that the minimum oil pressure may be specified at the outlet of the oil pump at 10 PSIG. My question is why is there such a difference between the 97 and the 03? I see the numbers that you guys are talking about on the 97, but the 03 runs much lower and seems to be much more variable. It doesn't get very cold here but I've never seen >80 PSIG. Ken Irwin

 

[nickleinonen]

that is enough oil pressure to keep the bearings from touching anything... i wouldn't much worry about it. a good reference for minimum oil pressure in automotive engines is about 10psi for every 1000rpm. . more than that and you are fine, less than that, and well, if you don't hear rod knock you are ok [sorta?] but more is better. at idle turing 750 rpm 6-7 psi is just fine...

 

[rbattelle]

Hmmm... very interesting. Now i see what you're talking about. But my question is: does the port to which you're referring take oil from the main rifle, or is it return oil coming down from the top of the head? Given the pressure you are able to get, I bet you're right and you are reading the main galley. I am at a complete loss as to whether it's a problem, though. And the real stinker is that if you take it to a dealer and complain, they will not have a CLUE what you are talking about.



How many miles do you have?

 

[rbattelle]

Well I'm conflicted. I tend to agree with Nick, but that's easy to say when it's not YOUR engine that's reading 6 psi!

 

[nickleinonen]

Originally posted by rbattelle

Well I'm conflicted. I tend to agree with Nick, but that's easy to say when it's not YOUR engine that's reading 6 psi!

i guess i should hook up a gauge to mine to see eh?

 

[mhenon]

oil pressure at idle.

Are you sure it's not just the change over from a 15w/40 dino oil to the 5W/40 synthetic?

I noticed that my idle pressure dropped a little after switching fron DELO 15w/40 to Mobile Delvac 1 5W/40 synthetic. I went on the Mobile web page and somewhere in there it said something about pressure dropping at an idle due to the lighter weight oil.

The running pressure is the same with the synthetic and the temps are down slightly so I'm not going to worry about it.



Mike

 

[rbattelle]

Okay, I have a recommendation. Kirwin, remove your sending unit from the current location and re-install it at the oil filter head. Then tell us what readings you get there. It's something to try, anyway!

 

[Kirwin]

Relocating sender

I'm at 17,500 miles and I run a stratapore filter. The oil pressures were measured both before and after the oil change at 15,000. Oil pressure was low before the switch but switching did lower it a couple of PSI. I will try relocating the oil sending unit to the oil filter port as soon as I fined the stupid plug that I took out of the engine to plug the hole I currently have the sender in. I don't think that this location is on the return line since it is the normal oil supply to the P 7100 pump and the old power steering/vacuum pump. Is the plug on the oil filter on the clean or dirty side of the filter? Thanks Ken Irwin

 

[rbattelle]

I think it's on the dirty side... someone correct me if I'm wrong.

 

[CumminsPuller]

Do most diesel engines run about 23-25 psi at idle once nice and hot? Then rise to about 50-60 cruising down the road? I am asking because I have an 8. 3C and am wondering what kind of oil pressure I am supposed to be looking at. The gauge on my 8. 3C seems to respond a lot quicker than in my dodge. Do most big trucks have mechanical gauges instead of electrical? I prefer the faster response.



Jason

 

[rbattelle]

Originally posted by CumminsPuller

Do most diesel engines run about 23-25 psi at idle once nice and hot? Then rise to about 50-60 cruising down the road? I am asking because I have an 8. 3C and am wondering what kind of oil pressure I am supposed to be looking at. The gauge on my 8. 3C seems to respond a lot quicker than in my dodge. Do most big trucks have mechanical gauges instead of electrical? I prefer the faster response.



Jason

I see 20 psi at hot idle, and 50-60 psi cruising down the road.

 

[CumminsPuller]

good... ..... was worried for a minute... ...