Repair a cracked plastic gas tank ?

[Sean McGillicuddy]

I have a plastic gas tank with a couple crack in the center of a flat spot.
How have you repaired it / can it be repaired?
Is there a tape like duct tape I can use?

 

[Vikestand]

JB Weld is about your only hope. Other than that, look for a replacement.

 

[jrems]

You can try a plastic welding tool. Harbor freight has a cheap model. It's a glorified soldering iron with a wide tip. I have fixed a few plastic gas tank on mowers just by heating the tip of an old flathead screwdriver with a lighter then holding the screwdriver on the crack until it melts and then cools. Do 1/4" at a time until the crack is melted back together.

 

[Grateful11]

I had a Shindaiwa trimmer that had a small crack in the fuel tank and tried some industrial epoxy, didn't work. What did work was a using a soldering iron to melt the crack back together after flushing the tank and drying it out. It was still holding when I sold it like 3 years after melting it back together.

 

[DoubleB]

Agree melting it closed is probably your best option. I suggest practicing on something else first, a risk is when you try to close the crack it only gets bigger, especially if the tank plastic is thin. What has worked well for me before fixing thin plastic is to set the cracked flat face on top of a spare scrap piece of the same material (probably HDPE) that is much bigger than the crack, then set those pieces on top of a flat piece of glass or maybe sheet metal. Then slowly heat the glass from underneath, focusing the heat to the cracked area. At first the spare piece of plastic will melt over the heat, then the tank settles by weight into the pool of melted plastic. Keep going long enough for the cracked area of the tank to melt, too, and bond well with the new plastic. Use glass big enough to support the non-melted parts of the tank, such that the tank keeps its shape and doesn't altogether crumple into a collapsed ball. Preferably, use a spare piece of plastic that is big enough that the perimeter of it won't melt.

I preferred glass because I could see the transition from solid to liquid plastic, which helped monitor progress. Also keep a compressed air nozzle nearby or some other way to gently but effectively cool the glass once done, so that its residual heat doesn't keep melting things once you've decided to stop.

Allow to cool and the HDPE should peel right off the glass/metal. I've just used chunks of milk jugs before. You could also double layer it if you wanted thicker.

Once done you'll probably have an unsightly perimeter of unmelted spare plastic around the weld. You can trim that off if you want, but I admit the repair is about function, not fashion.

Kind of an elaborate process, but it's worked well for me and very functional for those situations where worthwhile.

 

[Sean McGillicuddy]

I'm going to try "Seal-All"

I'll let you know how I make out!

 

[Giles]

I have a plastic gas tank with a couple crack in the center of a flat spot.
How have you repaired it / can it be repaired?
Is there a tape like duct tape I can use?

I have repaired several plastic Gas/Oil tanks. Never had much luck with melting or any type epoxy. I have found that a thorough cleaning and roughing up the surface to be sealed is more important then product you use.
After surface is prepared, seal with SealAll, a glue that is available at most auto parts stores and Amazon.
Sealing should be done on inside.
You might consider this after melting.

 

[gerry100]

gas cans and most gas tanks are made of High Density polyethylene mainly for resistance to hydrocarbons ( like gasoline), processibility and cost.

Because of this chemical resistance adhesives,glues etc are not very effective.

I'd spend the $20 bucks on a gas can ( if you have to buy one with one of those goofy/EPA spouts buy a funnel also)

IMHO, patching will be messy and possibly dangerous

 

[Jags]

Just a friendly reminder...

HGO2=B

Heat + Gas +Oxygen = BOOM.

 

[gzecc]

I've also gone the soldering iron route. It does work as long as it is the black plastic tank.

 

[Sean McGillicuddy]

Cracks are on a flat surface , so I went the easy way with "Seal All" I'll let you know how it worked out.

 

[gerry100]

I've also gone the soldering iron route. It does work as long as it is the black plastic tank.

Black plastic tanks are the same as red except for a different bit of pigment

 

[jetsam]

Just a friendly reminder...

HGO2=B

Heat + Gas +Oxygen = BOOM.

Ah yes, good old Vitamin B, one of the best elements on my periodic table.

I have an uncle who overdosed on Vitamin B while cutting an oil tank. It's not healthy to have too much all at once, apparently.