Over the last couple of weeks I have noticed a gradual decrease in oil pressure, -especially at hot idle. I have used delo 15-40 since I have had the truck, -and that's what was used in it prior to me owning it. I always use baldwin filters. Typically in the past, the thing would idle right at around 30 PSI hot with the 15-40, -and now it is around 20 (according to the factory gauge). I have not installed a mechanical test gauge to verify the factory gauge is correct.

It was time to change the oil, so I decided to try the delo straight 30 weight to see if it would make any difference, -it didn't.

One would certainly think that there would be a noticeable difference going from a multi-vis 15-40 to a straight-weight 30. The ambient temps here have been fairly consistent, -so no major swings in outside air temp. I do not have an oil temp gauge on the motor, so I have no reference in regards to oil temp. I did come home one night and left the truck running and ran some cold water over the oil cooler, -and after several minutes, it did kick the needle up about 5 PSI on the gauge.

I ordered a pressure sender for the factory gauge, and am going to pick it up on the way home from work tonight. Maybe it will make a difference, -maybe not, we'll see.

I recently read a similar thread that mentioned sludge-clumps in the pan. Man, I sure hope that's not the case. If that IS the case, and the pan has to come off, -new rod bearings are going in for sure, -as well as a new oil pump.

This seems awful strange. The motor seems to be running just fine, -no abnormal ticks, knocks, etc. Maybe I'm worried about nothing, -it's just that one doesn't typically see such a radical change in oil pressure like what has happened here.

Any thoughts or ideas?

I think the lowest you should see and still be safe is 10 psi at hot idle:eek:

You gotta put a mechanical gauge on to varify.

I have seen way too many inconsistencies with factory gauges. My gut tells me your fine, but you'll never know without the mechanical gauges second opinion.

It's not the beginning of the end. Put new ops and every thing will be fine. Had the same problem on my truck.

You gotta put a mechanical gauge on to varify.

I have seen way too many inconsistencies with factory gauges. My gut tells me your fine, but you'll never know without the mechanical gauges second opinion.
Yeah, I agree with ya 100% on that. I have a mechanical test guage at home with a 1/8" NPT end on it. I am thinking that may very well be what the threads are on the sending unit.

The oil pressure switch for the lift pump is completely independant of the sender, -so the truck should run with the sender unplugged (with the mechanical screwed in it's place), -shouldn't it?

I will try running the motor with the mechanical gauge installed and see what it says.

You can test a the front of the motor also, where the turbo gets it's oil, that should be the lowest reading.

You can test a the front of the motor also, where the turbo gets it's oil, that should be the lowest reading.
QM, -do I need to tee into that fitting in order to keep the oil line on the turbo intact during the test?

I'd sure hate to smoke my turbo bearings.

Thanks in advance,
Rich

May I suggest oil analysis if you still have a virgin sample of the 15w40.

It takes about ten minutes at idle before you hear the turbo bearings start to make noise from getting hot with no oil when the engine's cold. if the turbo is already hot, it maybe faster.

May I suggest oil analysis if you still have a virgin sample of the 15w40.
Like an idiot, I dumped the old oil into my 5 gallon waste oil pail out of habit.

I am really hoping it is an issue with the sender or the gauge in the instrument cluster.

QM, thanks for the info on the turbo bearings. I think I'm too much of a scared-ee pants to run the turbo without oil.

I will do the mechanical gauge test tonight and see what's shakin' inside the ol' 6.5.

Thanks for all the info guys, I appreciate it.

Rich.

Well, some good news, after some bad news first.

I swapped the OPS out tonight and used just about every bad word in my vocabulary. First the plastic piece broke off, -then after applying some pretty serious torque trying to get it off, I decided it was a bad idea to wrench the brass elbow off in the block. SO, I attempted to unscrew the brass elbow that the OPS is screwed into, -and it still wouldn't make a complete revolution due to the wrench hex on the OPS still being on there, so out came the die grinder. I scored the side of the OPS threads and was able to snap it off (allowing the brass elbow to unscrew without hitting anything). I then was able to extract the piece in the elbow in the vise on the workbench.

A real big pain in the Censored, but I got 'er done. The good news is that the new OPS brought the cold idle pressure up to 50 PSI, and hot idle at 35 PSI. I ran short on time tonight as it was getting dark, so I have not done the test with the mechanical gauge yet, -but AM going to do so in the next night or two. I have a feeling the motor is just fine, -which puts me at ease.

Now I need to fix those leaking oil cooler lines and oil filter adapter.............

I'll post what my snap-on test gauge shows for pressure, -and may post a small picture of what remains of the old OPS, -it is in three mangled pieces! I am also thinking that it might be a good idea to get a short piece of that aeroquip 1/4" hose and put the OPS on the firewall where it is remote mounted and easier to get to next time. After the ordeal tonight, I would sure like to meet the guy that decided to put the OPS there, -obviously he's never turned a wrench in his life, -what a knucklehead.

Just thought I'd give an update. I remote mounted the OPS and installed a brass tee (mechanical test gauge port for doing any future testing). Since I used a short piece of hose to get the OPS out of the bowels of the engine compartment, I had to add a short ground wire to the OPS since it was isolated from ground due to the hose. The ground wire is merely hose-clamped to the hex on the OPS for now, but I plan on removing the brass tee and making several wraps with the wire and silver soldering the ground wire right to the tee (where the OPS is screwed in at).

The really good news is that the factory gauge seems to be within a couple of PSI of the mechanical test-gauge, and cold oil pressure (at idle) with the delo SAE-30 is right around 45 PSI. So it looks like the bottom-end of the ol' 6.5 is alive and well.

I'm really diggin' the remote OPS, -it will make life much easier in the future should I have to change it out.

If I get around to it, I'll post a couple of pics tomorrow night.

Thanks to everyone who lended comments and advice, I appreciate it.

Rich.