Fuel Tank Leak

[vipermike]

I have a 2009 F350 diesel with a RDS auxiliary tank that I installed myself about seven years ago. I bought the install kit although there was no room for the check ball so I removed it and installed a straight in connector. There is a valve on the auxiliary tank but I always left it open. When fueling I would fill the truck tank first then the auxiliary tank. I would fill both tanks full. I never opened the truck tank while there was fuel in the auxiliary tank. I never had an issue with until the last time I fueled up. I mainly use the truck for towing the 5th wheel or trips to Home Depot for large items. So I filled the the truck tank full and then proceeded to put 10 gallons in the auxiliary tank. A couple of days later I noticed a puddle of diesel fuel under the truck. Both sides of the truck fuel tank was soaked with diesel. I closed the valve on the auxiliary tank and a couple of days later the fuel on the truck tank cleared up. I thought a seal may have started leaking so I called RDS and told him my story and he said that there is a check valve on the top of the truck tank so that fuel doesn't leak out in the event of a rollover. Has anyone experienced this or know if this check valve exists?
Thanks,

[DadsHemi]

Yes they exist, not a good idea to remove the check valve.

[bshgto]

Originally Posted by vipermike

I have a 2009 F350 diesel with a RDS auxiliary tank that I installed myself about seven years ago. I bought the install kit although there was no room for the check ball so I removed it and installed a straight in connector. There is a valve on the auxiliary tank but I always left it open. When fueling I would fill the truck tank first then the auxiliary tank. I would fill both tanks full. I never opened the truck tank while there was fuel in the auxiliary tank. I never had an issue with until the last time I fueled up. I mainly use the truck for towing the 5th wheel or trips to Home Depot for large items. So I filled the the truck tank full and then proceeded to put 10 gallons in the auxiliary tank. A couple of days later I noticed a puddle of diesel fuel under the truck. Both sides of the truck fuel tank was soaked with diesel. I closed the valve on the auxiliary tank and a couple of days later the fuel on the truck tank cleared up. I thought a seal may have started leaking so I called RDS and told him my story and he said that there is a check valve on the top of the truck tank so that fuel doesn't leak out in the event of a rollover. Has anyone experienced this or know if this check valve exists?
Thanks,

I put a 63 gallon RDS tank in the back of the truck and connected it to the fuel tank like you. everything went well for a time then went out to the garage one day and had a LARGE puddle of diesel on the floor. Turned the tank valve off and it stop leaking but mine was coming out of the cap WHAT MESS TO CLEAN UP. The next time this happened after replacing the cap it was leaking out of the tank it came from the top. I siphon a couple of gallons out to stop the leak. If you ever find the roll over valve post a pic of it I couldn`t find one with the limited space to see it with out dropping the tank. I think the head pressure from all that fuel pushing down is just to much for both parts. I just keep the valve closed all the time like I should have from the beginning unless it`s in use now.

[mhs4771]

I've had the same thing with my Chevy, and agree if both tanks are full it seems the extra pressure will push fuel out the top of the main tank. Closing the shutoff on the Aux tank stops the leakage. Only seems to happen when sitting unused for a period of time because when on the road traveling every few days no problem.

[Baldicon]

I think you are supposed to only fill the aux tank to 90% capacity to allow room for expansion.

[wed]

I have a f350 and have moved my tank between 3 trucks I just use the new Ford hook up each time.

[Montana Man]

A rollover check valve is designed for just that, a rollover. Gravity feeding is different. It is best to learn to use gravity feed in a manner that doesn't rely on the valve to do something it wasn't designed to do.

[Arkware]

I too have a RDS tank in my F350 w/gravity feed.
The only time I've had it overflow is after filling it full and then letting the truck sit in the sun.
I'm thinking the heat caused the fuel to expand causing the overflow.
It has never done that since.