Which mastic to seal a petrol tank?

trouville

trouville

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My outboard tank has a broken joint where the fule indicator plate is and when fullish smells of petrol,i cant leave it on deck as that the same as it going overboard! I tried polysulfide, buttal rubber and now silicon.Non work for long.

Which mastics petrol proof?? /forums/images/graemlins/confused.gif
 
There are some epoxies which are marketed as "Liquid Metal" or such. My bro-in-law used some to seal his remote tank in a similar position to your crack.
Be careful as some of the products are literally liquid whereas some are a paste and much easier to use.
Halford is a good source.

Just looked and the one I have is called J-B Kwik Weld.
 
What with your recent excursions into the field of explosive gas / air mixtures vis acetylene thread I would have thought you would value your boat and life a little higher. However if you insist, is the tank plastic? if so why not try to hot weld it with a soldering iron or one of the hot weld glues available. If you do this take the tank off empty it and flush it through with steam for a quarter of an hour, preferably till you cant smell petrol fumes. Use a kettle and keep the heat source away from the tank more preferable keep the tank purged whilst doing the work. I cant really recommend that you persue this course of action but with your track record it will almost certainly appeal to you. Please be carefull it would be shame to loose such a prolific and amusing contributor. The plus side would be if you fail you will almost certainly top the Darwin Awards entries for this year.

Good Luck
 
If its plastic, junk it. New ones are not expensive - sounds like you may already have spent the cost of a new tank on different gunges top fix the old one!

If its metal, then car manufacturers do a range of specific sealers such as Petro Patch for fuel tanks.

But I never managed to get any of them to work when I had a leaky Motorcycle petrol tank either! I never did find anything that stayed put for long. One Motorcycle breaker offered to weld it for me though...... I was tempted, just to see it go bang /forums/images/graemlins/crazy.gif
 
You would have waited in vain. A petrol tank with petrol in it, does not contain an explosive mixture. For petrol to go bang you need 6 to 15 % of petrol vapour in air. A tank is filled with 100% petrol vapour which due to lack of oxygen will not burn at all. Your breaker knew what he was doing!

So if your steel petrol tank has a crack, you can weld it or braze it. Done my motorcycle tanks a number of times without any explosions(!) .Empty the tank but leave about one litre in and shake it well so you are certain there is only petrol vapour in it. Seal all openings with grease, position it with the crack on top and weld/braze it. The escaping petrol vapour will burn until you have closed the crack.

regards,
Theo.
 
Is that post made tongue in cheek?

If not it is highly dangerous advice,and should not be offered on a public forum.

The fact that you have done it and got away with it is neither here nor there,it is a procedure fraught with very real danger.
 
Wholeheartedly agree, perhaps two candidates for the Darwin Awards, which is OK as long as they dont involve the rest of us.
 
... sorry, still waiting for the bang.

What you suggest honestly sounds b****y dangerous to me, without very careful preparation and a fair degree of skill and insight.

FWIW I do know how to prepare and weld petrol tanks safely. But would never, ever, suggest it should even be tried by Jo Bloggs with his Halfords welding set, and Haynes Welding manual.

To coin a phrase: Caveat Poster: Dont encourage amateurs to try something that is only barely safe to do even with professional insight and skills!

I also know the capabilities (lack of!) of the idiot who wanted to try doing it for me - and believe me, the bang would have been a big one the way he suggested!
 
Its a metal tank ive kept it painted and rust free but the screws holding the plate are set in!There was is a joint but thats leaking.Half full it dosent smell but fullish i get petrol fumes in the bilge and cabin.

When im sailing i have it on deck but tied up thats a sure way to loose it!I left a lead diving belt weight covered over with anchor line and that went!!

For some reason a local garagist who has a fishing boat (a fisher 25!) said welding was out!Though he was smoking while looking at it. Flushing and so forths still not 100%?

I was looking at acetalene lighting in the meuseum yesterday and they had a high pressure bottel as well as low pressure, but if it give carbon monoxide thats not so good!

Ill have to do something¨!

A note about heating when its chilly as now im useing about£2 (3 euros) diesel a day, a place in port with power costs about 4 euros £2.30 a day!!!

Im not keen on plastic tanks yet.

I know there is a mastic product but i just cant remember the name.??
 
I agree, my sugestion complete with warning was for the flameless but still iffy repair of a plastic tank. Having followed many of Trouvilles postings he appears pennyless and is willing to give most things a go to repair rather than buy new, a sentiment that I share and so the suggestion was offered.
However having seen and heard the results of an idiot atempting to braze a petrol tank connected to the exhaust of a running car to flush the fumes or so he said I can only agree and if attempted you wouldnt have to wait long for the bang which along with the flattened out tank is quite impressive.
 
[ QUOTE ]
Is that post made tongue in cheek?

If not it is highly dangerous advice,and should not be offered on a public forum.

The fact that you have done it and got away with it is neither here nor there,it is a procedure fraught with very real danger.

[/ QUOTE ]

Nothing dangerous or mysterious about this.
Fact:
Petrol vapour without oxygen is harmless! Remember you need fuel and oxygen and ignition to start a fire. If one of the three is absent, no fire!
Fact:
Petrol explosions happen when petrol vapour and the correct amount of air are mixed and ignited.
Fact:
Trying to clean a petrol tank by filling it with hot water of blowing lots of air in it is very dangerous as it gives a false feeling of safety. Just some droplets of petrol left over in some corner will produce the explosive mix you want to avoid and the potential bang is there.

But if you are really scared of petrol
Drop some dry ice in the "empty" tank and wait for it to fill with carbon dioxide before welding.


Trouville, do not ever put your leaking tank inside your boat unless you prefer sort distance flying over sailing. If you smell petrol inside, open all floorboards and ventilate.
Better loose the tank than your life. For emergency repairs use ordinary soap. Rub this into the crack as a temporary repair until you can replace of repair the tank.
Sorry, but I do not know of a "mastic" that will withstand petrol as you need it.

Regards,
Theo.
 
Plastic padding do a 2 part mix called chemical metal that is meant to be petrol resistant. Sets hard like the normal plastic padding. Halfords do or used to a joint sealer for engines etc to replace askets. One was called Rolls Royce Blue or Blue Halmar ? This worked well on various cars when I was in to rebuilding when a student .....
 
Well Theo at least we agree on the advice to Trouville about keeping the leaky tank out of his boat: Trouville, this really is serious - if you can smell the petrol inside the boat, then there is a very real probability that you will not be posting here much longer! In a confined space Petrol really is very dangerous stuff, and the vapour can ignite and flash back to the tank from an astonishingly long way.

Plastic tanks dont sound very safe, I know, but in a marine environment where rust can eat its way through thin steel very rapidly, I would go for plastic every time.
 
Advice understood,Tanks empty at the moment and im going to look at palstic tanks,

Ill start saveing,just theres so many things at this time of the year that need money!New depth new GPS?? Anti fouling and soon paint!And many small items that mount up.

CHIP OIL!!! Why hadent i thought of that??

Last year i even tried to change my petrol landrover for a diesel one to run it on chip oil (it seems the injectors will fur up and the pump will wear out) If i add petrol to chip oil to thin it down, that should heat just as well as diesel??Im off to ask how much petrol is mixed with chip oil 20% i think??

Im in my place with power now,not so much fun hear but i paid from Jan to april so im useing a fan heater which is nuclear powered! Care of the EDF (electricity France)
 
I'd stick to less technical things.

French Farmer

It is also dangerous to talk of such things

"Rudolph Diesel had designed the Diesel engine to run a variety of fuels and during his Paris speech said, 'the diesel engine can be fed with vegetable oils and will help considerably in the development of the agriculture of the countries which use it.'

A few years later Rudolph Diesel’s body was found floating face down in the English Channel. After holding secret talks with the UK navy about fitting diesel engines into their submarine fleet Rudolph Diesel was killed by the French to stop his diesel technology being fitted into submarines over the world. "
 
I looked at the liquid metal but there wasent i dont think there was plastic padding either??

I have to leave the EEC for a week or two.I might find it while im outside the EEC where anything usefuls been banned!

When i get back ill experiment with old engin and chip oil!I want to try useing a domestic heater carberetta instead of drip feed as well,to develop a heater for next season.

The only snag is garages and returants give the stuff away in 100s of liters? Some garages use their oil to heat.Collection and storage might need some thought.
 
For a short period of time plain chip oil in a diesel will not do much harm. The cause of the problem in diesel engines is the cold oil coming into contact with the engine and it turning into a gum/varnish (it's the glycerols in the oil that do this at low temperatures). For long term use of chip oil in an engine you neet to do one of two things:-
1) Turn it into bio diesel and get rid of the glycerols. How to do this at home is described at http://journeytoforever.org/biodiesel_aleksnew.html .
or
2) Install an oil pre-heater & a diesel swap system to run the engine on diesel for 5 minutes while it warms up, chip oil when travelling and 5 minutes on diesel just before stopping to flush the injectors with diesel. This strikes me as a particularly good implementation for a boat. According to the 'Eureka' design magazine, in a van you should get about 300 miles per gallon of diesel with an automated controller see http://www.eurekamagazine.co.uk/article/...e6t7ifNZaMGjxUA

I haven't yet used either process, but within the next year or so I intend to make muy own biodiesel for my van. I'm just not certain of the tax I've got to pay to the voracious robber in Whitehall.

Neither system is simple, but the results can be cheaper than sticking with diesel.

Regards

Richard.
 
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