Anyone know how engine oil would be leaking by the air and fuel lines going into the fuel tank?


Asked by Jan 29, 2014 at 08:09 PM about the 1998 Ford F-150 XLT Extended Cab SB

Question type: Maintenance & Repair

1998 Ford F-150.  There are absolutely no leaks in the engine compartment and the
underside of the engine is absolutely leak free.  However, there is oil literally dripping from
the frame right by the fuel inlet to the tank.  The frame in front of and behind this location
is bone dry.  How can oil from the engine get there?  The bottom of the gas tank and the
surrounding area is covered in engine oil

17 Answers


Sure its oil and not brake fluid?

1 of 1 people found this helpful.

Or gasoline?


How about transmission fluid, output shaft seal leaking, driveline slinging it as you go down the road, or if rear fuel tank pinion seal leaking.

1 of 1 people found this helpful.

I think you may be on to something with a Pinion Seal. Those 8.8" rear ends go through a lot of Axle seals and Bearings too. Is the Backing plate or inside of the wheel wet with oil too? If so, axle seal, bearing or axle has failed.


Absolutely positive it is not brake fluid, gasoline or gear oil, etc. It is engine oil. The pinion seal is not leaking, the differential is not leaking, axle seals are not leaking everything is dry in front of the gas tank and behind it. Back plates and wheel wells are dry too. Nothing is being slung. I know it sounds like I don't know what I am talking about, but I do. I am very knowledgeable about vehicles, build my own engines, have a race car and have worked on cars for the past 35 years. But this one has me stumped. This is oil. I am loosing about 2 quarts of oil every 1000 miles. The engine compartment is bone dry. Value covers don't leak, rear main doesn't leak, oil pan doesn't leak...everything under the engine is dry like a new car.

1 of 1 people found this helpful.

Is there any way something spilled in the bed or got under the bed liner?

1 of 1 people found this helpful.

Lol. I was thinking the same thing. Sure can't seem to wrap my head around what William has going on with his truck.


That's the only way I could think oil would get there dandy.


there is nothing there that would hold engine oil or have it passing by. It's either something else or its getting slung there from a much worse leak, but that would be noticable in other locations.


Appreciate all the suggestions but still no help. Nothing spilled in the bed, not getting slung, etc. I have been loosing about 2 quarts of engine oil about every 1200 miles and have not been able to determine why until I found this leak. Motor isn't leaking, isn't burning oil, nothing. I'm just wondering if there is any way that something in the engine breathing systems are blocked and backing up and sending the oil through the vent lines that go to the gas tank that maintain air pressure in the tank. I've checked the PVC and it is clear. I used to think I was a relatively smart guy when it came to figuring out problems, but this one has me stumped.


Some of these were known to leak oil at the back of the head from the head gasket on the engine and run down but you should be able to see or smell it. How many miles are on it?


There are no leaks on the engine anywhere. It is totally dry everywhere. Has about 180K

1 of 1 people found this helpful.

But if you having to add 2 quarts every 1200 miles it's either burning it or there is a leak somewhere. Keep us informed on what you find.


Agree, and it's not burning oil. No smoke, no smell, nothing. Although it sounds inpossible, the leak is back by the gas tank and I have yet to determine why.


Any luck figuring it out William?


Not yet

Did u ever find the problem leak or burning I go with burning 2 quarts is to much to leak without a sign. Let us know thanks

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