Low oil pressure on 4104 671

[JT4104]

My 671 as of late has lost oil pressure after warming up to where it is only showing 5-6 lbs pressure on idle.

When I start it, it shows 40 psi on idle, 60-70 psi on high rpm.

When harmed up, even on high rpm's it won't go above 30 psi and my dash meter shows no pressure (although the oil guage on the engine shows 5-6 psi).

Using 40 weight shell rotella, changed the oil and filter but same problem.

Time for a new oil pump?  Any suggestions would be appreciated.

JT4104

[Busted Knuckle]

JT Since you've changed the oil & filter, you've eliminated the posibility of old broke down oil. But don't go rushing to change that oil pump just yet (not saying it may not need one), first off do both guages get there pressure from the same location? BK

[JT4104]

Hi BK!

The oil pressure hose comes out LH side of the block (see pic) then runs up to a manifold mounted on the bulkhead with the pressure sender (right), low pressure sensor (left) and mechanical guage mounted (see pic 2).

As I said, the pressure is strong when I start cold but quickly drops in about 10 min to almost nothing on idle, shows about 5 psi on mechanical guage in back and barely anything on dash.

Any help would be greatly appreciated.

JT4104

[Busted Knuckle]

JT first thing I'd do is check that hose since all the readings are coming from that location, old hoses have a tendency to either colapse, or break up inside. Which could mean a blockage that clogs shor4tly after starting it. On the other hand it could be the pump, worn bearings, clogged passages, clogged filters in the oil cooler, or many other variables. I'm no expert, but if all the gauges use the same location I suspect that could be where the problem might be. I've got an 8V92 DDEC that does the same thing, the front gauges barely shows anything, the rear shows about 5, but the DDEC will shut it down at anything less than 7 psi, I know the DDEC part works as I had 6 out of 8 injectors leaking fuel in the oil when I first got it and it would dilute the oil to the point of shutting down, change the oil and 60 psi again at first then it'd go back down. The first trip I took it on I changed oil in the hotel parking lot 3 nights in a row and once after dropping the people off, and got it home and fixed it (after finding the bad injectors). We've run it 3 yrs now and still going strong! I plan to do an inframe this winter, but as long as she's got enough pressure to keep the DDEC happy I'm happy! Hope this helps guide you in the right direction!
  Knuckle

[JT4104]

Ill take down and flush out the hose and manifold.  I don't know if I have a filter in the oil cooler but I'll look into it.

I don't believe I have any fuel in the oil.

Thanks for your suggestions.

[Busted Knuckle]

JT, Yeah I don't think ya got fuel in the oil either I was just using that to explain the way mine did! But the hoses or blockage, bearings, etc. are possible causes.
  Knuckle [/b]

[DrivingMissLazy]

Isn't that about normal for an older engine? As i recall, my 671 was very similar to that.
Richard

My 671 as of late has lost oil pressure after warming up to where it is only showing 5-6 lbs pressure on idle.

When I start it, it shows 40 psi on idle, 60-70 psi on high rpm.

When harmed up, even on high rpm's it won't go above 30 psi and my dash meter shows no pressure (although the oil guage on the engine shows 5-6 psi).

Using 40 weight shell rotella, changed the oil and filter but same problem.

Time for a new oil pump?  Any suggestions would be appreciated.

JT4104

[gus]

My 671 oil press is very low at idle when hot but I'm using 30W oil, I don't think any 671 has much pressure at idle.

I would  replace the rear gage with a new gage and see what that shows. It is normal for the rear gage to be higher than the front but don't know the reason for this. Maybe because the electric wire is so long?

I'm assuming the crankcase is full or near full. The 671 is very sensitive to low oil levels.

[JT4104]

Hey, if that is normal, I'd be happy to know that as well.  Anyone know what the oil pressure on an "average" 4104 6-71 (warm) should be on idle?

[Busted Knuckle]

JT I have no clue as to what a normal 6-71 is since I've only ever even seen but 1 (many years ago! LOL) but my Daddy has always told me if ya gi=ot some oil pressure at idle yer OK even as low as 5 lbs. Well back when I was racing stock cars I had one awsome engine that would only hold 5-8 lbs. of pressure at idle, Daddy kept tell'n me son don't worry aboutit as long as it has good pressure while cranking out the rpm's "Don't try to fix somethin that ai'n't broke!!" Well I was stuborn and hard headed and put a new high volume oil pump in it and well since I had it out before putting that new pump in I tweaked it with a couple washers to make the spring tighter, WOW! 80 PSI at idle! Daddy told son you done messed up the best engine you ever built! Daddy knew what he was talking about first night I raced after "fixing it" I blew the engine in the middle of the feature. When we tore it down first thing Daddy pointed out was "well son, looks as though youwashed the bearings right out of it!"!  Might point is some oil pressure is better than none! But too much is bad also! BK!

[Len Silva]

I think you are fairly normal.  Mine will run at around 30 psi at speed but drop enough to cause the low oil light to flicker a bit at a stop light after a hard run.

Len

[JT4104]

Took down and cleaned out the oil pressure line and manifold; actually, hose to manifold not that old and it appears to flow well, cleaned the sensors and guage, pulled the oil pan and checked the screen everthing looks okay, oil is new 40 wt, so I guess it is either the oil pump or 5-7 psi on idle is normal as fellow busnuts have indicated.

Thanks for all of your input.

JT4104

[TomC]

The first Diesel truck I drove had the screaming 238 (6-71N) in it.  It also had marginal oil pressure at idle, and once warmed up had 32psi at 2100.  I never checked the oil since the engine used to tell me it needed another gallon when the oil pressure got down to 28psi at 2100.  With the 10 speed, upshifted at 2,400rpm and down shifted at 2,000rpm.  Never hurt the engine, and two drivers after me also ran the truck.  Although the engine did get destroyed after the Mt St Helens volcano blow in the 80's because it had a hole in the clean side of the air intake and sucked in some of the highly abrasive silica volcanic dust that literally ground down the piston rings. 
If your engine is not burning excess oil (more than 800miles per gallon), doesn't overheat, and doesn't light up the low oil light at idle, I'd say don't worry.  If you do have the oil pan off, check the bearings.  Just as a matter of fact, I'd roll in new bearings while you're at it since the bearings are relatively cheap, compared to a spun bearing taking out the crankshaft.  Good Luck, TomC

[NCbob]

Dumb question....can't remember.  I'm thinking pressure relief valve spring worn?  Like I said I can't remember for sure but I'm almost positive that DD's have a pressure relief valve and it might be sticking open and allowing the OP to fall at idle? 

My shot in the dark! 

NCbob

[WEC4104]

Found the attached info in some DD stuff I had, hope it is helpful. (Also hope this image attaches properly)

FWIW, my 4104 has always had very low readings on the dash gauge at idle.