Hey all,

My truck started acting up the other day. Every now and then the oil pressure gauge drops to zero. It only happens for a few seconds, and engine RPM is not a factor. This morning the gauge bottomed out and the oil light came on (a first for the light). I'm thinking sending unit, as I've read on the 4.6/5.4 side that this is a common problem. The truck is a '99 F350 with 81,000 miles. WHen this problem occurs, there's no rattling or clacking from the engine indicating low oil pressure, and the truck starts and runs like a champ. Any ideas?

 

I agree with you, sounds like the sending unit is going bad. Replace it with a known good one and verify it. If it;s not the sending unit, might be wire connection to it or at a terminal point someplace. Biggest reason I'm installing another set of water temp/ oil pressure gauges to verify my factory ones. Cheap insurance.

 

I know this sounds funny, but make sure you have oil. My 2000 did the same thing. The gauge flickered like crazy, the light came on, but the motor made no noise, no lifter noise, nothing and it was almost out of oil. I know it sounds stupid, but I figured I'd ask.

 

Again, here's a follow-up that I neglected to post when I first fixed the problem. So I went to the parts store to get the sending unit; turns out there's two different ones for the V-10. I bought both (they were cheap, and I didn't know which one I needed) and I figured that I'd do an oil change while I was down there. I get home, let things cool a bit, and pull the plug. Roger, you were right on the money. It was waaaaay low on oil! I figured that since it doesn't leak oil, and it doesn't smoke, it should still have all the dino-juice it needed. Wrong answer...and it was only 4,000 miles since the last oil change! I topped off the crankcase and the problem disappeared. Imagine that. He he...I'm almost ashamed to admit that I'm ASE certified...

 

i've been having terrible oil consumption problems in my 2002 F350 V10 Triton. last month i had the same problem you described - started up and a few seconds later the pressure bottomed out, caused apparently by way low oil. i still haven't figured out where all the oil is going (no leaks that i can find, no excessive smoking). i do have some white vapor and mild white smoking at startup and have developed a somewhat less smooth idle when not in park or neutral. 171k miles.

any suggestions about where the oil is going and whether the idle problem is related?

 

Man, if its not leaking it, or burning it, and its not in the crank case, it must be in the cooling system, but that's a lot of oil, however the white smoke upon start up sounds like a weeping head gasket. Exhaust gasses in the radiator are easy to test for.
I hope Im wrong.

 

i can manage a lot of maintenance and usually follow the discussion, but i'm no mechanic. is this test something a quick study can do herself?

i also want to note that the truck was being used over the last couple months under pretty extreme conditions - towing a 9500 lb dump trailer, sometimes loaded for up to a total of about 20,000 lbs, on the highway and in landfill. towed the 9500 lbs back and forth between dallas and houston several times. it still consumes a lot of oil even when not towing though. i just this last oil change put back in the 5w20 - the last place put in 5w30 and i have no idea what the place before that put in it, but i had been adding 10w30 before i learned it called for 5w20 (just got the truck at end of sept). i may have run it for about 1500 miles with mostly 10w30 in there before i had the oil changed - i was adding more than a quart a day for a couple weeks when operating under heavy load.

i have added fuel inj cleaner twice over last 6k miles (thought may have gotten some watery gas) and tried an oil additive that claimed to stop consumption about 600 miles ago - no change. i've heard the horror stories about changing the spark plugs in this truck, but that was going to be my next step to address the rough idle. should i hold off until i find out if i need a head gasket? (i actually thought white smoke and vapor at startup was either valves or running too rich - is this wrong?)

sorry so long, but i wanted to make sure i didn't leave anything important out. i'd really like to keep this truck running a bit longer. THANKS!

 

I read you post completely, and you can use either 5W-20 or 5W-30 oil, it doesn't matter. But from what you have told us, it sound like the oil is going through the engine, and working it hard wont hurt it, just dont overheat it.
Checking for exhaust gas in the radiator is easy if you have the equipment, and most dont, but all shops do, and it only takes a minute. But I'm leaning towards the PCV valve being stuck open, its a small valve in a hose on the outside of the engine (on this engine, I think it is), cheap and easy to replace.
If the problem is not that, you may need to have a leak down test conducted on the engine, this is a larger and time consuming job, (and replace the spark plugs at the same time, they have to remove them anyway) and it will tell the condition of the valves and rings, and the general condition of the engine.
I still think that with this low mileage it should still be in good condition. Working it hard should not hurt it, its a truck engine.
In most cases burning oil produces blue smoke, and not just on start up, and white is coolant, but you have added way to much oil to be having it going in to the cooling system.
You may need to find a good shop, but not a dealers service dept, I dont trust them.
And have it tested for high oil consumption. This engine is not know for using much oil.
Good luck, and keep us posted.
Mike.

 

Reasons like this are why I check my oil, and coolant levels at every gas fill up.

Hope your motors okay after being starved for oil.

 

yeah - i checked my oil at every fill up (which in this case was every day), but at first thought i just wasn't getting a good read on the dipstick. there was always oil up the edges of the stick and i kept adding oil, then started worrying that i was adding too much because i couldn't believe it was using that much with no sign of where it was going. that's when i had the oil changed, so i could see if the dipstick got a good read, which it did. this confirmed that it really was using the oil. it was the morning after i drove it to dallas from houston that i started it up and the pressure bottomed out, so it consumed enough oil on that one trip to cause this to happen (hasn't happened since).

 

Schooner 45, I would tend to think that your truck is just fine. You live in Texas where the humidity is at or above 50% most of the time. The white 'smoke' you see on cold start up is condensation that has formed in the exhaust. When you shut off a hot truck and let it cool overnight, it will draw moisture out of the air into the exhaust system as it cools. When you start it up the next AM, there it comes out as white 'smoke'.
As for the oil consumption, I tend to disagree with mikehm. The V-10 has 2 more cylinders to keep oiled than a V-8 and will naturally use a bit more oil. I have a 2001 F-350 with close to the same miles as yours and no matter how it is used, I am 1 quart low at around 2500 to 3000 miles. You will not see the blue smoke normally associated with oil burning engines because it is such a minute amount that gets burned off as the engine runs. The spark plugs usually don't show any sign of fouling either.
And don't be afraid to work your V-10. I pull a 28' fifth-wheel travel trailer with mine and don't cut it any slack. Just make sure you are up on maintainence and drop the hammer!!
Happy motoring.