Low oil pressure in N14 Cummins

[Mountain Flyer]

Greetings,

I have a 1999 International Eagle tractor with an N14-370 ESP engine... it runs good, has good power, uses maybe a gallon of oil every 12-1500 miles. However, the oil pressure runs low. At 1500 rpm cruising in high gear, about 25-30 PSI at normal operating temperatures. At idle it drops below 20psi. On climbing some long hills with a load on recently, the "low oil warning" has come on near the top of the hill. Dropping to a lower gear it goes off; stopped and checked oil (within the lines)... so it has oil... but not enough pressure. The previous owner claimed to have replaced the bottom bearings not long ago. Engine has 456,000 miles. Any clues???

[mrpersons]

mountain flyer If that was my buggy, I'd be heading down to the shop pretty quick! Not only is your oil pressure on the low side, you're consumption is high also. You're sure that milage is accurate. Have you checked for fuel in the oil? That milage is pretty low to require a bearing replacement also, so I would be suspicious of the reason that was done, and also if it was done correctly and by who.

Did you just buy this truck???

[bentpole]

Cam bearings?

[Mountain Flyer]

I bought the truck in November, and just put it on the road in January. I have only been about 7,000 miles in it so far. It was my first truck; I am the first to admit I didn't know much about what I was doing when I bought it. It is a nice chassis & interior; the engine was a bit suspect and I wondered the same thing when he told me that but felt I could trust the guy

Live and learn. Just don't know what causes it. Oil use might be a bit high I guess.

[One]

first ting todo is tohave the oil pressure checked by a shop. theyll pull the sensor out and replace it with their gauge, so you will be able to find out if ur gauge is accurate for starters. If they crank- bearings were replaced, surely they checked/cleaned the oil pickup in your oil- sump and the seal on it. im noot sure if the symptoms point to a weak oil pump or not...It is possible that there is excessive clearance in your engine allowing the oil to flow through too easy.

[Nulldev]

Fuel dilution can reduce oil pressure (smell dipstick for diesel), but you would normally expect the level of oil to go up over time (more fuel dumped into engine).

I'd get it checked out either way.

[Mountain Flyer]

I appreciate the advice guys. If anyone has more, bring it on. I have a run tomorrow and when I get back will try to schedule it into the shop to have it checked. Just sux as a new owner operator to have to think about putting thousands more into the rig, but such is life... :? Maybe it is as One sez, an oil pump. Just my gut tells me there is something more to it. I do get some pretty good oil leaking out of the blowby tube onto the ground, which leads me to think I've got problems there too....... sigh. :shock:

[Windwalker]

The previous owner claimed to have replaced the bottom bearings not long ago. Engine has 456,000 miles. Any clues???

My first question would have been "WHY NEW BEARINGS SO YOUNG???"
An N-14 should be able to run a million miles without things like bearings having to be replaced. Or is the correct mileage 456,000 plus a million??? If that's the case, plan on an oil pump, sleeves, rings, pistons...

I nearly walked away from my truck because the N-14 had a complete rebuild at 422,000. Then I found out the previous owner ran it without filters in the air-cleaners. Then too, what kind of work did it do before? A '99 with 456K??? Mine is a "00 and has almost 700K, and it sat out of service for a year. How does a "99 only have that many miles on it???

[Mountain Flyer]

You may be onto something Windwalker. This owner had three of these trucks; he purchased them from Walmart; they are old Walmart fleet trucks. One of them have over a million miles but had a new Detroit Diesel. Second one he claimed had 600k. This one 456k.

As I said, I am a damn newbie in this line of work and took him at his word; I didn't know what questions to ask. This unit was the niceset of the three as far as body, interior, etc. went; I figured that the one with the lowest miles would be the best investment, even if it needed work. In retrospect the high mileage truck with the new engine may have been a better choice.

I paid 20K for the truck so figured even if I needed an inframe or whatever I would still not be into it too deep. (but who wants to pay for an overhaul in your first year when freight prices and volume are sucking as bad as right now!)

I wondered about the bottom bearings too; thought the same thing you did. I did a lot of homework before buying, but still as I said, I am new at this and should have spent a hundred bux to have a mechanic look at it. Might have saved me thousands.

I just came back from a long, hard run from Idaho into Montana and back. Lots of hills; grinding up and jaking down. Truck ran well and since we put a manual fan switch in, I just turn the fan on at the bottom of the hill and run it all the way up. Even Whitebird Hill (20 mins and it is one steep mother) at 80,000 pounds I never got the temp over 185 and the oil pressure stayed steady (albeit still below 30#).

I added a 3 quart jug of Power Service Oil Extender just before leaving on this trip, and upon return home I am only down about 1 quart, so that makes me smile. It was a long, hard run for the truck (and the driver )

Well, time will tell. I am just going to keep the oil up, watch the gauges, and hang on until I get the truck down to my friend's shop in Twin Falls to have him put it on the computer and check the gauges, etc.. then we'll know more I guess.

I appreciate everyone's help. You guys rock.

[BIG AL]

if it happenned all of a sudden it's most likely a piston cooler broke. the coolers are nozzles made of plastic located behind the 6 inspection covers on the right side of block and they spray oil on the bottom side of the pistons to cool them. if you let them run like this (besides the low oil press) the piston dome will crack

[Mountain Flyer]

Thanks Big Al, I will pass that on to the mechanics when I have it looked at. IT is staying about the same; running 28# or so at normal road temps and RPM's., and has been that way for the 15,000 miles I have put on it so far. I found some good Cummins mechanics at a shop in Twin Falls, ID;;;; just have to make time to schedule it in for them to check it out. Kind of afraid what they will find so am kinda not in a big hurry if you know what I mean...

[Mountain Flyer]

Big Al and One were both on target... had the truck checked Friday; had one piston cooler that they replaced and they also took the piston out of the oil pump and cleaned it up. The combination bumped my oil pressure from the low 20's to almost 30 p.s.i.. The mechanic said for Cummins about 30# or a little over is average anyhow, so I can sleep much better now... 8) The truck runs well otherwise and has good power; doesn't smoke, and what oil it uses it mostly leaks out, rather than burns from what I can tell.

Anyhow, thanks boys for the suggestions.

[tumbo1]

had the samw thing in my western star 13psi at idle and 31 at 1500 i also thought this was low for a motor with under 200,000 on an inframe when i took it to the dealer they manually checked and showed me the cummings specs for the n14 in there book and 10 psi at idle is within spec and 30 psi at 1400 so you are right were you are supposed to be :P

[Windwalker]

Mine has about 22 psi at an idle, and at 1400 rpm, it's up to over 38psi.

[csramsey640]

Same here, I have heard from a cummins mechanic that higher oil pressures in a n14 will beat the cam bearings up pretty bad. Ours runs about 40 psi or so at 1500, 724k

[bob h]

Big Al and One were both on target... had the truck checked Friday; had one piston cooler that they replaced and they also took the piston out of the oil pump and cleaned it up. The combination bumped my oil pressure from the low 20's to almost 30 p.s.i.. The mechanic said for Cummins about 30# or a little over is average anyhow, so I can sleep much better now... 8) The truck runs well otherwise and has good power; doesn't smoke, and what oil it uses it mostly leaks out, rather than burns from what I can tell.

Anyhow, thanks boys for the suggestions.

The cooling nozzle should have shown a "sudden" change in the oil pressure; when they break, it creates a leak in the main oil gallery. If the cause was bearings, the change would come over time... almost unnoticably. Fuel will thin-out the oil (not too common in N14s), if it's a slow internal leak, the pressure will go down as the oil change interval comes to it's end. If the internal fuel leak is severe, the engine oil level will rise (overfull). The thin oil can cause a blow-by condition, which will cause blue smoke from the stack.

Doesn't hurt to at least "inspect" the rod and main bearings (bottom end) at 500,000 miles, especially if you didn't buy the engine new. The engine may have suffered head gasket or rocker gasket internal leaks (quite possible) which contaminates the oil and "wipes" the bearings. Watch the oil; conatminated oil will become sludgy (texture) or milky in appearance.

...Overhaul @ 1,000,000 , bottom end @ 1/2 way to overhaul.

The oil leak to "beware of" is behind the accessory drive pulley... if it leaks, it CAN cause major problems, have it checked right away!!!

Oh, and the 1st step in oil pressure diagnose is ALWAYS checking pressure with a "known good" manual gauge.

[Mountain Flyer]

I still have low pressure in the N14. The repairs they made ( I posted earlier) helped some... for awhile... but I am now back to running about 25 p.s.i. at cruise speeds. When climbing a long hill on a warm day, if I don't gear down and RPM up sufficiently, I will get a Low Oil Pressure alarm on the dash.

Otherwise, she runs fine and does not use much oil (drips mostly). Previous owner replaced the bottom bearings but I wonder if they botched the job?

[stranger]

One way to check for worn main and rod bearings:

When loaded, while driving steady on level ground , at say 1500 or so rpm, give the truck full throttle. Note the oil pressure under throttle.

Let off on the throttle completely and let the engine hold back. Stay the same rpm and speed as you were when at full throttle.

Watch the oil gauge. If the needle jumps more than a couple of pounds you have bad bearings.

This test had been right every time I have seen a 4 to 5 lb or more increase in oil pressure between pulling and holding back at the same rpm.

[Mountain Flyer]

I will try that test!