Okay I have a 99 Dakota r/t with 43k miles. About a week ago the oil pressure gauge kept dropping to zero and then right back up. I went on a 500 mile trip to OH from VA. Still did the dropping so in Ohio I bought a new oil pressure sending unit but didn't replace. I did disconnected the old one and reconnected it. I had no problems on the way back til about 2 minutes away from my destination in VA. Started dropping again. When I arrived I checked the oil and the dipstick was almost completely dry. I have no oil leak anywhere and just did an oil change about 1500 miles ago with synthetic oil. Where should I start? Should I replace the sending unit and do an oil change again? I am somewhat lost here, not really sure why the dipstick would be dry if I a not losing oil anywhere. Anyone know what is going on or has had the same problem?

 

Sorry I didn't realize I was in the wrong section

 

I'll move it for you. No worries.

 

Did you change the oil or a shop?


If you did it did you run the engine for a few minutes then recheck the oil level and on a level ground?


You can have an oil leak only as you drive and never see anything under the truck.
That's why you should check your oil level 1 or 2 times a month its cheap insurance.

 

I agree with 98dakaz. Who performed the oil change and was the oil checked right after to make sure the amount was right?

You don't necessarily have to leak oil, it can be blown past worn rings and out the tail pipe. I'm puzzled that you observed dropping oil pressure and messed with the oil pressure switch, yet it seems that you didn't check the oil, even before going on a 1000 mile trip (RT). How many times has the oil been run low? You might want to check your coolant too... a dry engine tends to burn it.

 

FWIW, I had an oil leak when driving (oil filter was loose), and I never lost oil pressure. Came in for oil change, guy goes "You had more oil in the filter than the pan!". Then he looked at the filter seat and noticed it had been spraying out towards the back.

It doesn't take much oil to keep pressure, and I never had any rod knock or lifter signs or anything.

 

I did the oil change my self at the auto hobby shop on base. I checked the oil afterwards was fine. I checked the oil when the oil pressure gauge went down it was also fine at that time. There was a thread on here saying change your oil pressure sending unit if your gauge goes down and back up with regular oil levels. The oil has never ran low before.

 

The sending unit is a common problem. IMO its rare that your pump would go.

From what I understood is that you bought the unit but still haven't replaced it?

Of course you should replace it and fill it up with oil. Will take you no more than 5 mins.

 

Okay, thanks for clarifying. I couldn't tell these things from your initial post. How long have you had the vehicle? The oil pressure switch won't make much difference unless you're blowing oil right through the switch. Bad reporting and losing massive oil are two different beasts.

According to the math, you began your trip with only 500 miles - post a fresh oil change + good oil level. You lost all the oil within a 1000 mile trip? For that to be caused by blow-by, you'd probably see smoke coming out the tail pipe. It's possible that you might be leaking oil while the engine is under compression vs a standing drip with engine off. Even so, hard to believe you wouldn't see oil residue somewhere. This is a tough one without actually seeing the vehicle. I say you have a leak... somewhere. If you cant find one, you may want to have compression tests done. A good mechanic might be worth a try in this case.

 

well I started the truck and let it run for a few then checked the oil and it was normal. Why would the dipstick not have oil at 1st, is that common after a long trip? I think I'll might replace the sending unit and oil and see what happens. What is the best synthetic oil for our trucks? If I replace it and still have problems with the oil pressure gauge where should I start to look then?