diesel fuel leak

[johnhicks]

I have a 1993 HR on a Oshkosh/Freightliner XC chassis, and I have a fuel dribble.

What's happening is that the fuel tank is chock-full, filled it up and drove all of six miles, and now I get a fuel drip that's originating on the top of the tank. It didn't drip last time I filled up and then drove 100 miles but now it'd dripping with the full tank.

This has happened before but it's so rare that I park with a completely full tank it's hard to pin down.

The filler hose was replaced a couple of years ago.

So...is there anything on the top of the tank that fuel could expand out of or seep out of due to unlevel? Seems to me I read something about that but of course now I have no idea.

[johnhicks]

This morning, no drips. This afternoon at 84F, drips. OK, that's two days now that it drips only when temp increases. I've removed the cap and vented the tank twice. So I suppose it's expansion that pushes fuel out of wherever it pushes it out of.

In my case "this day and age" is 23 years ago. I had it worked on three years ago to replace leaking filler hose. Part of that work order with Cummins states "replaced fuel breather line."

So OK it's a quirk. I believe this is the second time I've parked with the tank filled to practically overflowing.

BTW, I might drip half a cup a day, so no biggie. But of course I prefer to not drip or dribble.

[Blaster_Man]

American Coach '09 Allegiance. As I said before, I could lay on my back and watch the fuel drip out of the over flow tube...I put an can under it, didn't drain much maybe a quart.

[usersmanual]

Blaster Man wrote:

usersmanual wrote:

Blaster Man wrote:
On my last two diesels, if I topped it off during the summer, both would expand enough to leak out the over flow tube. I could lay on my back underneath the coaches and see where it was coming out of the tubes.

why in the ell would there be a overflow tube on a fuel tank?

For the same reason there is an overflow tube in your radiator. When 150 gallons of fuel gets hot it expands...has to go some where.

I seriously doubt there are overflow tubes on any fuel tank in this day and age. What year and model did u own that had this so called overflow tube on it??

I will add maybe there was 20 years ago but with emission controls there is no way there is a overflow tube on any fuel tank and has not been any for quit a few years.there are one way vented roll over valves but totally different deal
99.9% of the time if u overfill the tank it will expand up the vent and fill hoses
If you do overfill your tank and its leaking underneath you have a leaking vent or fill hose connection or sending unit. there are no overflow tubes on fuel tanks in this day and age
I personaly doubt there ever was any but there are strange things in all events at times

[Bill_Satellite]

I had a leaking fuel sending unit on the top of my diesel tank. The only way to see/access the top of the tank was to remove a rear panel in the back of one of the storage compartments. If you have this kind of access you should be able to easily see the top of the tank and likely identify the source of the leak.

[steppinstone]

Blaster Man wrote:

usersmanual wrote:

Blaster Man wrote:
On my last two diesels, if I topped it off during the summer, both would expand enough to leak out the over flow tube. I could lay on my back underneath the coaches and see where it was coming out of the tubes.

why in the ell would there be a overflow tube on a fuel tank?

For the same reason there is an overflow tube in your radiator. When 150 gallons of fuel gets hot it expands...has to go some where.

quote===x2

[Blaster_Man]

usersmanual wrote:

Blaster Man wrote:
On my last two diesels, if I topped it off during the summer, both would expand enough to leak out the over flow tube. I could lay on my back underneath the coaches and see where it was coming out of the tubes.

why in the ell would there be a overflow tube on a fuel tank?

For the same reason there is an overflow tube in your radiator. When 150 gallons of fuel gets hot it expands...has to go some where.

[johnhicks]

I looked this morning when it had cold-soaked at 58F, no drips.

[usersmanual]

Blaster Man wrote:
On my last two diesels, if I topped it off during the summer, both would expand enough to leak out the over flow tube. I could lay on my back underneath the coaches and see where it was coming out of the tubes.

why in the ell would there be a overflow tube on a fuel tank?

[Blaster_Man]

On my last two diesels, if I topped it off during the summer, both would expand enough to leak out the over flow tube. I could lay on my back underneath the coaches and see where it was coming out of the tubes.

[usersmanual]

steppinstone wrote:
what is the temp where you are? If you fill your tank to the max and sitting unlevel and it's very warm out the fuel will expand so most likely it's the vent.IMHO I would take it for a good ride and burn off a little fuel.

what vent would be on a fuel tank that allows fuel to leak all over due to expansion?? pray tell

[usersmanual]

johnhicks wrote:
Thanks folks. So far I haven't been able to squiggle into position to see the top of the tank.

When I filled up air temp was about 88F and I did fill it right up to pump shutoff, so I too think it's probably expansion.

expansion is BS the only way that would be a problem is if it was leaking out the filler cap area as I said if u read reply's most likely sending unit or The loose filler hose or vent hose connection
or bad hoses

[johnhicks]

Thanks folks. So far I haven't been able to squiggle into position to see the top of the tank.

When I filled up air temp was about 88F and I did fill it right up to pump shutoff, so I too think it's probably expansion.

[steppinstone]

what is the temp where you are? If you fill your tank to the max and sitting unlevel and it's very warm out the fuel will expand so most likely it's the vent.IMHO I would take it for a good ride and burn off a little fuel.

[Scottiemom]

Check to make sure your filler hose is tight. We had one leaking last year on our Freightliner. It was loose. DH tightened it down and we were good to go. That was AFTER a service by a Freightliner RV Oasis authorized service center.

Dale