Remote oil tank leaking or ??????

[w2much]

I just looked into the bilge of my Nitro restore boat. It has a Johnson 1991 150 on it. In the bilge area was a bit of a mess, almost a quart of 2 cycle oil. I filled the remote 1.8 gallon tank almost to the brim. I did this in order to check my oil consumption while I was running on premix 50 to 1. . I can not tell how the oil is escaping the remote tank. I can understand the tank leaking from the gasket if filled to the. I do not see how or why the tank could empty about 1 inch of oil from the tank.. I wrapped the oil line and bulb with paper towels to see if the line was leaking at primer bulb. It was not. The towels were still clean.
When I squeezed the remote tank I heard air and oil bubbles from what appears to be two square vents in the oil pickup assembly. . Any thoughts on how my remote oil reservoir could dump a bunch of oil while just sitting for a few months.

 

[Grub54891]

Clean everything up spotless, lay some white oil sorbs in the suspect areas and run it. You will find the leak.

 

[dingbat]

How old is the tank?

Ive changed out two tanks due to oil permeating thru the tank walls. Both roughly 10 years old

 

[w2much]

That was how I started. Everything spotless, clean towels in place.
That is what I am going to do again. I did run it and did take it out after my first initial clean up and no sign of a leak immediately thereafter..
Mr Dingbat, that is a weird phenomenon . Can that really happen ? I have not heard of this. To my logical side I say that can not happen, oil can not leak through its oil container. My situation says it seems like that is what is happening. Its like seeing a ghost, did I really s********Can that really happen.
If there is a vacuum leak in the oil line or the oil side of the VRO pump that can cause oil to flow backwards from the higher engine back to the tank which is lower. I can see that happening. If the tank is full to the brim the oil must exit the vents. This I can see. But the tank lost another pint or more likely a quart of oil. This is over 3 months or so, boat sitting idle on the trailer
I like having the VRO but may go to premix if there is a ghost.
I just thought. Oil from the engine could only go backwards as far as the primer bulb, not back to the tank. Shot my own theory down. Anyway can oil permeate the walls of the remote tank? I need a fix.

 

[boobie]

You could have a bad cap on the oil tank let it building up pressure when sitting.

 

[w2much]

I am looking for reasons and then solutions. If the cap were bad, allowing pressure to build where and in what form would it exit. The oil pickup assembly has the two square or rectangular vents, does it not? I can see possibly my cap vent was turned to close venting from the cap but would it not vent are the assembly then ?

 

[Joe Reeves]

Where is this oil tank situated that oil could escape to the bilge?

 

[dingbat]

Mr Dingbat, that is a weird phenomenon . Can that really happen ? I have not heard of this. To my logical side I say that can not happen, oil can not leak through its oil container.

Not weird at all. The permeability of hydrocarbons in plastics is a well understood phenomenon.

To be an effective barrier, it is necessary for that barrier to not just maintain its physical integrity when exposed to chemicals, but to also perform as a barrier.

Whilst chemical resistance tests provide a measure of resilience, the measure of barrier performance is the permeation rate. This is where HDPE fails as a hydrocarbon resistant barrier because polyethylene and other common homogeneous geosynthetic membrane materials are readily permeable to hydrocarbons, because they are hydrocarbons themselves.

https://www.pollutionsolutions-onlin.../1219/download

As I said earlier, you're not going to loose an 1" of oil from the tank in 2-3 months thru permeability. The oil I was loosing wasn't noticeable. I just couldn't keep the tank clean. I'd remove the tank it and clean it to like new. Three months later the tank and the surrounding area where covered with oil again. New tank, problem went away.

Air bubbles tells me you have a leak in the feed hose. I would pull the hose running from the remote tank to the fuel pump and inspect for damage or leaks. My oil primer bulb is and stays harder than a rock

 

[w2much]

The oil tank is not in the bilge but above it on the floor, back of the boat with the batteries. The boat is on a trailer with the bow high so as to drain water. The oil just drained down stream and ends up in the bilge by the drain. The bow was not really high, prob just a bit above level which is why it made such a mess. It had a larger area to spread out.
Great stuff on the permeability. My tank is always oily to touch. I am going to lean towards aanother tank and line with bulb.

 

[w2much]

You could have a bad cap on the oil tank let it building up pressure when sitting.

Checked the tank area today and found another mess. The motor has not been run. I put a tray under the tank so the cleanup up was relatively easy. Yesterday hit the high 80s low 90s , relevant I guess to Boobies suggestion of pressure building inside if the tank. I could see that the oil again escaped from the oil pickup at the new gasket I installed. I took the cap off the tank and tried to blow air and parts cleaner through the hole in the brass thingy on the inside of the cap to the outside. Apparently the cap did not vent. It had a cap on it that looks as if it belongs there. I went to the junk pile and grabbed another cap. I checked it the same way I did on the other cap and it vented. I understand how heat pressure and expansion can work. Isn't the oil line one piece inside of the oil pickup then into the tank to the screen at the bottom of the tank? ? The tank is filled to about an inch below full.