Fuel Tank Sealant Leak

[ladauphine]

Has anyone had a fuel tank leak due to the disintegration of the black sealant on the plates and screws holding them in the depression on top of the tank. My 2006 42DS fuel tank started leaking last summer due to the sealant disintegrating when the tank was full and the diesal fuel weeping up through the screws heads. Had to pull the plates and screws and reseal. Anywhere there is any of the old sealant left, it disintegrates when exposed to diesal fuel

[reverie]

I also had a puddle of diesel fuel in the depression on top of my tank last summer after i filled the tank. I have a 2004 S035. I mopped up the fuel with some paper towel, and it seems to have stayed dry - but likely because the level in the tank dropped as I used the engine.

I haven't yet addressed the situation - I'm still in monitoring mode. But would love to know how other folks have fixed this!

[grantgoulding]

I regulary have the weeping fuel problem on my 2006 42ds. I have yet to find a way to fix it. I would suggest the method of fastening to the plastic tanks is inadequate. Much prefer stainless tanks. Another cost cutting exercise. All I can do is to ensure we don't overfill which on a tank so small means even less of a range. Anyone have any ideas (apart from buying an older boat!)

[ladauphine]

My mechanic unfastened the round plates and thoroughly cleaned all of the original black sealant off everything- plates screws and depression. He wired brushed the screws and plates and resealed everything with permatex moto one. After curing, we refilled the tank and it doesn't leak-so far. You must remove all of the old black sealant or it will continue to disintegrate and the tank will leak again.

[MikeNW]

I have a 2005 Sun Fast 35 with the same problem. The seal around the fuel pickup for the diesel heater started leaking after I filled the tank in Oct 2009. A local marine engine mechanic attempted to fix it in May 2010. He cleaned off the old sealant and replaced it with a generous amount of Permatex (not sure which exact product). It seemed to hold over the summer. However, I just filled the tank yesterday, and it is leaking again.

I would appreciate any advice out there regarding long-term fixes that have worked reliably. Is your fix still holding ladauphine?

Read on if you want more info on my specific problem and what I have learned:

*********************

The tank on my boat is polyethylene plastic (LDPE?). The tank walls clearly can flex with pressure changes and movement of the fuel within the tank.

The diesel heater was added by Jeanneau at the factory. They cut small holes in the tank for the pickup tubes, then fastened the pickup to the tank using a chemical sealant plus some screws. The screws were driven directly into the plastic. There is no backing plate, so it is difficult to tighten the screws sufficiently to create a good seal. Effectively, they are relying on the integrity of the chemical gasket.

According to a contact at Jeanneau, the factory used an acetic silicone sealant supplied by Jacret for the diesel heater pickups. The sealant used on the engine fuel pickups is Loctite 5970. I have not had a problem with those pickups thus far, but I did notice that bits of the cured sealant around the edge of the pickup plate are now starting to crack.

I consulted several people in the local marine industry regarding this issue back in the spring. None of them had seen the problem before. They told me that most plastic marine fuel tanks used in the USA have screw threads and/or backing plates and/or female receptacles molded directly into the tanks. The tanks are also made from a rigid plastic that does not flex nearly as much as the one from Jeanneau.

The alternate suggestions that I have received thus far involve cutting a larger hole and installing a backing plate, plus possibly a mechancial gasket. This may require a new fuel pickup assembly. I have not yet been able to locate off the shelf parts for doing this. If anyone knows of a source for these parts in the USA, I would appreciate a referral.

[caoimhin]

I have just cleaned out my tank and I noticed the black sealant breaking away. I think bolts and nuts might be the way to go. You would need to put the bolt in upside down and the fix the nut on top > I might try and fit some type of gasket

[ladauphine]

Yes my fix mentioned above is still holding. I last visually checked it in September and the fix shows no sign if delaminating or leaking. I was on th boat today and did not notice any problem. I keep my tank pretty full so it would leak if the sealant failed. I think the key is total removal of the old black sealant, wire brush the area including the screws and heavily coat the surfaces with the moto one sealant. Will continue to monitor and advise . Best of luck!

[MikeNW]

Followup on the situation with my boat: In March 2011, a local boat yard fabricated and installed a new fuel pickup to replace the original part. The new pickup has a backing plate. Since then, I have not seen any more fuel leaking from this pickup.

[ladauphine]

So in October, 2011 I filled the fuel tank to reduce the condensation over the winter. Three weeks later, the diesal fuel had delaminated the sealant and we had fuel weeping out into the bilge. I contacted my dealer and he sent one of his mechanics out and resealed the fittings on top of the tank. The key was he sealed both the backing plate inside the tank and on the top. I think the real solution is 1. Never fill the tank to the top if you are not going to burn off fuel. or 2. Put a new tank in that is not as flexible and/or as cheap as the factory supplied plastic tank. We have closely monitored this problem for 5 years on our boat and a new tank seems to be the only permanent solution. Any thoughts?

[charlesriley]

I'm using the LevelPro leak detection sensor device for a long time without any trouble and also the support team is very helpful. So you can check this device from Icon Process Controls website: iconprocon.com/product/ld-leak-detection-sensor/

[saltymetals]

I realise this is an old thread that i have stumbled upon but i had exactly the same problem with the large diameter sealing washer where the L-piece for the filler tube i fixed to the plastic tank. The washer had gone all soft and had expanded leaving gaps around the edge so i got a bilge full of diesel every time i refuelled. My temporary solution was about 10 nappies/daipers stuffed around the recesses under the tank.

There is a plate underneath the L-piece for the filler tube so the tank needs to be empty to be able to get access underneath. 

The marina technician fixed it for me with a new washer in the correct diesel-resistant material saying that Jeanneau had used a washer made with material that was not suited to diesel and would eventually soften/expand/break up.  (My 43ds is 2004 so this repair was done after 15 years)

With so many reports on this thread of exactly the same problem you would have thought that Jeanneau would have learnt by now. 

[Mistroma]

I've obviously been very lucky with the sensor hole on my 42DS tank. It has been removed and re-fitted twice a year since about 2012 (possibly 2011). I syphon out from inside the tiny sump at the lowest corner. I've been getting progressively larger amounts of crud over the years. Probably a half teaspoon in 2012 and now about a litre or two of cloudy fuel and an egg cup of black material. Most of the "contaminant" is probably the result of fuel degradation plus a small amount of diesel bug. I double does with Marine16 for last fill and last fill of each season.

I clean the depression and gasket thoroughly before wiping with acetone. I smear a little neutral cure sealant on all surfaces before reassembling. The depression is filled with neutral cure sealant after tightening down and excess smoothed off. I'm careful not to over-tighten the screws.

No sign of any leaks yet, probably means it is guaranteed to leak next year.

[leehadjiosif]

Mar 25, 2010 4:20:21 GMT ladauphine said:

Has anyone had a fuel tank leak due to the disintegration of the black sealant on the plates and screws holding them in the depression on top of the tank. My 2006 42DS fuel tank started leaking last summer due to the sealant disintegrating when the tank was full and the diesal fuel weeping up through the screws heads. Had to pull the plates and screws and reseal. Anywhere there is any of the old sealant left, it disintegrates when exposed to diesal fuel

My 42DS was leaking fuel from the top of the fuel level sensor which was held in place with sheet metal screws. I took the opportunity to replace the sensor with a better one and put a lot of RTV (black) on the contact faces and smeared a lot on top of the screws and edge of plate. Now I have a new sensor and no leaks. In case you don't know, the RTV is for making high temperature gaskets on cars and other machinery and is sold at automotive stores.

[Mistroma]

I used black RTV for the first 2-3 years and then had to switch because I couldn't get it nearby in Spain. It did work well.

I used moisture curing sealant after that (mostly from Toolstation). I think that I used translucent StixAll last year. No problems with leaks so far. StixAll adheres well to most things but I don't think it will be difficult to remove from the tank as the plastic is pretty slippy.

I'm careful to avoid excess squeezing out inside the gasket to avoid it dropping into the tank.