Help Needed 99 7.3L Oil Pressure Problem.

[KTMMDG]

Hey let me first start off as, this is A 1999 Ford F350 7.3Liter Diesel Truck.

275,000Miles I am the second Owner, The original Owner bought this truck Brand new. I have all of his service Records.
He kept this truck clean and serviced it every 3,000miles.

I know he hauled and used this truck as it was meant to be used. things done on the truck have been.- 1inch Blocks. 35inch All terrain Tires. Banks Power Stinger Plus System. Custom Automatic Transmission with Suncoast Converter, TransGo Tugger Kit, Alto Clutch Packs, Mag-Hytech Pan. 456 gear Ratio.

The High Pressure Oil Pump was replaced at 175,000miles
all Ford Recalled items have been replaced.
other then that nothing else has been done.

Owned it for a while then the Problem started.

Fact 1. At idle the Dash gauge would sometimes flicker and the lite would come on. this would (return to normal) when the RPM was at or higher then 1,000RPM.

Fact 2. my Dad and I put a mechanical gauge on it. Oil Pressure at idle read Zero. at 2,000RPM it still read Zero.

Fact 3. We Diagnosed that, it could be the Oil pressure regulator valve. or the Engine Oil Pump.

Fact 4. Replaced the regulator valve unit. and Replaced the Engine Oil Pump with a Melling engine oil pump.

Fact 5. Put the Mechanical gauge back on. At cold idle read 50psi then slowly came down to 25psi at 2,000RPM read 50psi and held.

Fact 6. (took her up the hill. came back) At Hot idle read Zero. at 2,000RPM read just 25psi.

where's the Oil Going?!? although Replacing the Oil Pump and regulator valve unit made a big difference it's still not where it should be. The Engine is not Knocking it sounds great. so my Dad and I don't think its the main Bearings.

what else could it be? anywhere else the oil could be squeezing by? what I'm I missing here?

 

[BJS]

when you replaced the oil pump which one did you replace? the HPOP or the LPOP there are 2 on the PSD, the HPOP is in the valley, the LPOP is on the front of the crankshaft incorporated into the front timing cover

2nd where are you taking your oil pressure reading from. The easiest place to take it from is the hpop reservoir (where the factory sending unit is) there is a 2nd 1/4" npt port in there.

From reading your post it appears that you know the difference between the HPOP & LPOP but the 1st paragraph was just incase. There are a couple places to loose oil the main bearings and the cam bearings are the two most likely locations.

or the check valve in the return path from the HPOP reservoir is stuck slightly open.

 

[BIG JOE]

Hmmmm.....

Just food for thought ?

1. Why doesn't the PCM shut it down, due to Low oil pressure ? If, in fact, there is 0 oil pressure. (or not even let it start)

2. Are there any oil related DTC's ?

Seems like it's time for a Real Good diagnostic.. Scan ?

Joe

 

[DaveBen]

If he had zero oil pressure in the HPOP his truck would not start. Too much going on here to figure out without getting it scanned by a good mechanic.

Dave

 

[KTMMDG]

when you replaced the oil pump which one did you replace? the HPOP or the LPOP there are 2 on the PSD, the HPOP is in the valley, the LPOP is on the front of the crankshaft incorporated into the front timing cover

2nd where are you taking your oil pressure reading from. The easiest place to take it from is the hpop reservoir (where the factory sending unit is) there is a 2nd 1/4" npt port in there.

From reading your post it appears that you know the difference between the HPOP & LPOP but the 1st paragraph was just incase. There are a couple places to loose oil the main bearings and the cam bearings are the two most likely locations.

or the check valve in the return path from the HPOP reservoir is stuck slightly open.

I Replaced the LPOP. Yes I'm checking it from the oil reservoir where the factory sending unit is.
Do you think that the main bearings and the cam bearings would just fade like that? I mean the problem started instantly one day it's great the next the problem starts.
I will check the check valve and see what I find.

Hmmmm.....

Just food for thought ?

1. Why doesn't the PCM shut it down, due to Low oil pressure ? If, in fact, there is 0 oil pressure. (or not even let it start)

2. Are there any oil related DTC's ?

Seems like it's time for a Real Good diagnostic.. Scan ?

Joe

good question. it has to be getting a least a small amount.
I can start up. and it'll idle great and you can stomp on the pedal and it will haul booty. that's why I'm baffled by this problem performance wise it runs and sounds great.
no DTC's.

If he had zero oil pressure in the HPOP his truck would not start. Too much going on here to figure out without getting it scanned by a good mechanic.

Dave

Yes I've been thinking about taking it in to have it checked out.
But I'm going to try everything I can before that.
I've been making calls, hitting Forums and studying up like a mad man.

 

[DaveBen]

Yes I've been thinking about taking it in to have it checked out.
But I'm going to try everything I can before that.
I've been making calls, hitting Forums and studying up like a mad man.

We are all guessing at this point. These trucks are meant to be scanned. If you do get it scanned it will at least give you a direction to go. I can appreciate not wanting to spend a lot of money getting a diagnosis, but you are driving an expensive truck and you do need to spend a bit to keep it running. I bought an Auto Enginuity Scanning package for my laptop computer. I had it for weeks before my truck showed up. I have scanned everything in my neighborhood, it seems. Good Luck.

Dave

 

[Dogman]

Do you think that the main bearings and the cam bearings would just fade like that?

Yes.....But there could be other things too. Like a bad oil pick up..

 

[JLDickmon]

Yes.....But there could be other things too. Like a bad oil pick up..

good point.
I've heard of them coming loose, and also heard of them cracking..

either one would make it lose pressure to aeration..

 

[BIG JOE]

Yes.....But there could be other things too. Like a bad oil pick up..

good point.
I've heard of them coming loose, and also heard of them cracking..

either one would make it lose pressure to aeration..

But if it lost pressure.. wouldn't the PCM shut it down ??

Takes 500 (ish) HPOP psi to pop the injectors, at start.. he's got that.

IIRC, the PCM has Low oil psi parameters that will cause a PCM controlled shut down. That's not happen'n.

Hmmmmm. Gauge issues, or the psi source ? Or the check valve Brandon mentioned.

 

[Dogman]

The only other thing would be the test port is bad or gauge is bad.