Oil of some sort in the bilge..... Fuel tank leak?

[rwthomas1]

Hello All,
Day before yesterday upon checking the bilge in my '83 E38 I found a very small amount, maybe an ounce or two of light honey colored oil sitting on top of the water in the aftmost bilge well. Seemed heavier than diesel fuel, not black like engine oil would be and not red like the ATF in the transmission..... I have checked everywhere, thought maybe an oil container was leaking. Can't find anything. Yesterday I was out in some really snotty weather that shook a bunch of stuff loose. Yesterday there was some more oil in the bilge but it smelled a lot more like diesel yet still not dyed red like I see the diesel in the fuel filter..... Hmmm. Under the nav station seat and under the port side bench seat there is a slight oil residue in some places and it smells a bit like diesel but not as strong an aroma as I would expect. There is no smell in the boat, only when you wipe the oil and sniff it. What I am wondering is is it possible the fuel tank is leaking? I have checked all the fittings on the tank and they are dry. Its the original aluminum tank. Looks like a bit of cutting may be involved to get it out....... I have some oil absorbers in the bilge to catch anything that ends up there. Any input on this appreciated. Thanks, RT

 

[Annapolis E-27]

I went through a similar problem two seasons ago. It turned out that the aluminum tank had corroded at the lowest corner. What began as a pinhole leak of fuel in the bilge eventually resulted in hand pumping the bilge and tank to avoid any accidental diesel discharge via the bilge pump. As a temporary solution I plumbed in a three gallon tank. I think my ultimate solution will be to cut the top off the tank and use the open tank to hold a fuel bladder. This is easy with a Yanmar YSB engine as the fuel return goes directly back to the fuel pump and not the tank. As for the color, is there the chance that the tank has been previously filled with auto diesel, hence the lack of red dye?

 

[Loren Beach]

Mystery Colors and other Imponderables

Regarding the color (or lack) of the diesel...
What with the thriftiness of our diesel engines, I and many others at our moorage "jerry can" our fuel from the local truck stop or auto service station. We use stations that have a lot of volume in order to get freshest fuel. When you only need 5 or 10 gallons at a time it seems to make the most sense.
On small quantities, I do not worry too much about paying the hiway tax on it, but have bought it from the pump at the trucking part of their operation and filled out the extra form to avoid paying the tax. I gave that up when they eliminated the only pump station with a small nozzle...

I would note that I have not seen any dyed diesel for several years -- I wonder if they still have it?
All the diesel fuel I have seen is "clear" for quite a long time, now.

As to finding the odd source of an oil-related leak... Have you considered that the prior owner may have squirreled away a lube oil quart or gallon in some semi-hidden place and then forgotten about it? It's just the kind of action that a person might take for a "what if" spare that he/she will seldom use while on vacation. That and the double-secret stash of spare filters!

...So many nooks and crannies, so much memory loss...
(Boats can be like that. I have friends that were finding spare parts for several years after buying their used sailboats.)

Cheers,
Loren

 

[rwthomas1]

Thanks for the input,
Mark,
How long did it take your leak to go from a pinhole to a problem? I don't really want to tear my boat apart right in the middle of the season but if I have to I might as well get a jump on it.

Loren,
I have checked all nooks and crannies I can find and there is nothing hidden that could leak. Dyed off-road fuel is still available just about everywhere. I'm in construction so I see a lot of it. There is a local distributor that has it right at the pump. Technically I am not supposed to use it for the sailboat as "pleasure" use is supposed to pay tax. I use the 5 gallon jerry can for my "backhoe", the one with the 52 ft mast......

thanks, RT

 

[Annapolis E-27]

Rob,

It took the better part of 6 months to get bad. I was fortunate as when it really leaked I had already hauled for the year and the batteries were removed so the automatic bilge did not pump out what turned out to be approximately eight gallons of diesel over the course of two months of leaking while hauled.

I even tried to patch the tank with epoxy made to adhere to aluminum but apparently, diesel like water, will find its way out if there is a way. Good luck and keep plenty of oil absorb rags around.

 

[rwthomas1]

Well the fuel tank has a pinhole leak. I checked every fitting, union, hose, etc. and all were dry. I then removed the battery box and pushed it out to port and there was a pool of fuel under it. The bulkhead that is directly in front of the tank has fuel wetness between it and the tank.....

SO I CUT THE QUARTERBERTH FLOOR OUT!

I did a little surgery and cut around the trim and removed the entire deck section that covers the fuel tank. I then cut out the tabbing that I could get at that holds the tank. The tank is still pretty well attached so I will be removing the forward bulkhead tomorrow. I am planning on reconfiguring the tank location and the battery boxes. I think that I may have to cut the tank in half to get it out of the companionway. The result will be a different shape/sized tank to get the new one in. Either way the whole shebang will be new. I am going to give up 10gallons or so to gain space for 2 more house batteries. The existing tank is 56 gallons so if I end up with 45 gallons that will still be plenty, especially if I get more house battery capacity. So new bulkheads, tankage and battery boxes hopefully this week! Sucks to have to do this but at least I know the problem and one more system will have been completely redone. Will have pics tomorrow.

RT

 

[rwthomas1]

Update! some pics

Hello All,
Here is a couple shots of what is involved in removing a fuel tank from an early 80's E38. I cut out the battery box area and bulkhead as well for easier tank removal. The new tank will be shorter, approximately 40 gallons instead of 56. The reason is to make room for a larger battery box to accomodate a larger house battery bank. The new tank is being built by www.lutherswelding.com for @$650.00 Hopefully it will be ready in a week or so. Enjoy the pics! RT

 

[ted_reshetiloff]

Thanks for the post RT. Keep us up to date on the project. Did you end up having to cut the tank up to get it out? Was there no way to fit a non custom made tank into that spot? I know Tempo makes a lot of different size tanks.

 

[rwthomas1]

Ted,
I would have liked to go with a plastic tank but I couldn't find any that had the correct layout. The stock tank fits the hull contour and has the fill/vent in the aft so the quarterberth deck fits pretty flush to the tank. Fitting a Tempo or other square tank would require moving it all the way forward in that space, installing longer filler/vent hoses, relocating the batteries aft of the tank and likely giving up considerable tank volume. Not a compromise I am willing to make. Seemed like it would decrease the value of the boat in the long run. The new custom tank will be ready to install with new sender and all aluminum fuel fittings.

With a new short tank I should have about 40 gallons and room for 4 group 31 house batteries or 4 6volt golf cart batteries. Actually if I was to go to gel type batteries I could forego the battery box completely and have just enough room for 2 8D batteries in case I ever get to go cruising with this boat. Any of the combos will produce 400-450ah house banks. And this still leaves enough room under the nav station seat for a dedicated start battery. I have even considered 2 more group 31's or 2 more 6volts under the nav seat for a total of around 600ah's in the house bank. Then the dedicated start battery will be installed in a battery box behind the engine.

Glad you like the post, will update as it progresses. RT

 

[stbdtack]

Rob, I had the same problems you had with a pinhole leak. My suprise was when i got the tank out it wouldnt fit through the companionway. I ended up cutting off the corner of the tank. It only amounted to 1.5 gallons so I wasnt worried about loosing capacity.

I was lucky in that all the tank tabbing had let go so I was able to lift it out and was left with a perfect cradle for the new tank.

My corrosion was caused by water pooling under the lower corner of the tank. While it was out I ground out any obstructions that prevented water from draining and cleaned it all 5 times with acetone to get rid of the diesel smell.

One extra step i did was to glue lexan strips to the bottom of the tank so water would never be trapped against the aluminum.

BTW, I have four 235amphr golf cart batteries that fit in the original battery space.

 

[rwthomas1]

Hello Ben,
I found your earlier post on this topic and saw you went through basically the same thing. Ditto just about everything you said about how, where, why, etc. One question I have is how did you fit 4 golf cart batteries into the original space? Are you using the space under the nav station seat too? Where is your start battery? Thanks, RT

 

[stbdtack]

Rob,
My GC batteries fit in the original battery location. I had to cut a notch in the top edge so I could drop them down and slide into place. They fit snugly so it takes minimal securing. I refastened the cleats that support the battery floor since i was putting a lot more weight in.
235 Ahrs each bank

My start battery(group 24) is on a shelf I added just in front of the water heater.

 

[rwthomas1]

Thanks Ben,
My battery box looked original and was captive in that it couldn't be removed from the opening. I could loosen it and slide it back and forth but I would have had to cut it to get it out. The battery box was saturated with acid despite being lined with fiberglass as was the underlying supports, etc. This is partially what led to me cutting things up to make the battery area bigger. I want a separate box of epoxy/fiberglass to mount in the opening to contain the acid. Changing to AGM/Gel batteries would negate this but that is a much more expensive option. If I used AGM/Gel units I could probably get 6 golf cart batteries in the space I have now. The battery box I will build should hold 4 golf cart or 4 group 31's with ease. Having a house bank with 400+ ah's will be a welcome change! Will post pics of that when I get it done. Thanks, RT

 

[stbdtack]

rob,
good luck and keep us posted on how its progressing