Thread: Plastic fuel tank repair.

G'day Rob, There used to be an epoxy 2 part strip we used for steel fuel tanks....
I just did a "google search" for "cracked plastic fuel tank" and got a stack of options...have a look below.. Cheers, crowie

https://www.google.com.au/search?q=c...l=rcs&start=10

Originally Posted by rob streeper

I've got a cracked plastic fuel tank. Does anybody have any experience with the repair of these?

Rob,

Back in 2000 or 2001, I tried repairing a plastic fuel (petrol) tank. The crack looked like it had started at an impact point, probably caused by a stone impact. I don't remember what brand of Epoxy Ribbon I used (too long ago), but I tracked down the repair method on the Internet. As well as the recommended epoxy ribbon, there was a lot of information available on the Net regarding the actual repair technique - crack preparation (drill the ends of the crack to stop the crack spreading further, carving a "V" in the crack from both outside and inside the tank, thorough cleaning, and apply the epoxy ribbon on both the inside and the outside. Having to apply the epoxy on the inside means that in many cases the tank will not be repairable due to lack of access to the crack on the inside of the tank.

The 25mm crack that I tried (yea, I'll get to the "tried" part soon) to repair was located underneath the access point for the fuel sender unit, so luckily I could get to the crack from the inside as well as the outside. The repair looked sound when I'd finished, and when leak tested with a few litres of fuel, it held. So I filled the tank, monitored it closely for a few hours on the first day, and then daily for a few days.

Then I got complacent, and didn't bother checking anymore. About five days later, I arrived back at the car after doing the grocery shopping to find a fire engine next to my car hosing down a big fuel spill. When I had a look, I found that the crack had propogated about beyond the repair. I got a $180 bill from the Fire Brigade for the call-out and washdown, and the company that owned the supermarket sent me a huge bill for the "environmental clean-up of spilled petrol". Fortunately, my car insurance covered both of those bills.

I ended up buying a second hand replacement fuel tank from a wreckers - from memory it cost me about $60 for the tank, plus a bit of freight to get it home seeing my car was off the road.

A bloke at one of the wreckers did suggest that some Panel Beaters do plastic weld repairs to plastic fuel tanks. I checked that out before buying my second-hand tank, and found that because I had contaminated my plastic tank when I did the Epoxy Ribbon repair, that the first Panel beater I spoke to didn't think a plastic weld would take. However, that same Panel Beater told me that some Car Insurance Companies do not permit plastic fuel tanks to be repaired at all, and always replace cracked plastic fuel tanks with either new or used replacements. Two other Panel Beaters said that they always replace cracked plastic fuel tanks. Note: That was back in 2000ish, and the technology of plastic welding may have changed enough to make plastic weld repairs of fuel tanks more reliable now.

My recommendation - repair a plastic fuel tank with epoxy ribbon at your own risk. The cost of a failed repair will most likely exceed the the cost of replacing the cracked fuel tank with a new or used one. I'd only do an epoxy ribbon repair again as an emergency "get me home" repair - not as a permanent repair.

Plastic Weld repairs sound feasible, but if you have a common brand/model of car, a used fuel tank from the wreckers is probably the same price or maybe cheaper than a plastic weld repair.

Hope that information is useful....

Regards,

Roy

Hi Roy,

Thanks for the information. I've read similar reports about the failure of epoxy patches on the plastic gas tanks. The plastic welders seem like they have potential but I've not read any first-hand reports of their use on a fuel tank.

Cheers,
Rob

I repaired a tank because a replacement was not available for a long time and the car was needed.
Removed and filled it with water to remove any residual fuel then drained it, drilled small holes (1mm) at the ends of each fracture line, and a bigger one at the fracture point. Then using another tank at junk yard off a line trimmer that I cut into thin strips to use as "welding rods" using a temperature controlled soldering iron and melted or fused the holes closed . I checked it daily expecting a leak waiting for a tank but after several months cancelled the order. That was in 1990 on a 88 model I sold in 2004 and the car is apparently still on the road with 500000 more km on the clock after repair.
It takes patience and some experimentation to ensure perfect bonding and almost invisible repair. I used the donor tank to test the method first.

I've read about the soldering iron type plastic welders and am glad to hear that they work. I have reservations about attaining a good, full thickness bond. I've also seen the nitrogen welders and am wondering how they work.

Thanks,
Rob

Rob, I do agree if the crack is long this would be a challenge. I had never viewed any YouTube of this until today. I have a flat bit. I had a single hole with a dent and a few short cracks radiating outward. The ends could be sealed with a soldering hole I think, but a flat bit gave we a much smoother surface and I could layer the plastic into it bottom to outside then by heating the cracks and when soft (plastic goes clear) fill with new. Today I made a tray out of milk containers to soak a long antique plane I bought in Evapo-rust. Worked well, but has a tiny leak. They are good practice being thin, and they melt quickly so it gets skill up fast. I always practice a bit before making welds.
Nitrogen, not heard of that but I will look into it a bit.
I often repair electronic test instrument cases with a soldering iron so neatness and strength rather than a perfect seal is what is needed.

Mike,

Here's a link to the type of plastic welder I'm talking about http://www.usplastic.com/catalog/ite...FVCCMgodPToARw. It looks to be an amped-up soldering iron with a gas port. I haven't read any reviews and I don't know if it is appropriate for fuel tank repairs.

Cheers,
Rob

Thought you might find this article interesting ......

http://www.iapd.org/dwp_test/pdf/tips_welding_thermoplastics.pdf


Also found another article on the net last night (can't find it again now to post the link - sorry). That article was almost identical to the above link as far as technical content went (e.g. the welding temperatures quoted are the same in both articles). What the article did recommend was the use of a Digital Remote Infrared Temperature Sensor (e.g. something like this http://www.amazon.com/Raytek-MT4-Non.../dp/B0002198GY) to get the temperature correct. The second article said that the use of a compressed air heat gun at about 5 PSI air pressure was faster for production work than using an electric soldering iron.

The other interesting bit of information from the second article was that for welding PVC type plastics, which are apparently difficult to weld because the weld temperature is very close to the char temperature for PVC, substitution of nitrogen at 5 PSI minimises the PVC charring.

I've also watched a few Youtube videos of people demonstrating how to plastic weld a fuel tank. I don't know whether it's just me, but there seem to be some real shonky plastic welders doing commercial work out there in Youtube land. One bloke says that he does plastic fuel tank repairs as part of his employment - and his welds looks so daggy, with minimal depth to the weld, and what weld has been deposited appears to be very porous ..... Here's his Youtube link if you're interested: https://www.youtube.com/watch?v=EbtUxJJs8G0 (If you don't want to watch this all the way through, jump to the 2 minute mark.)

Roy,

Thanks for the info - very useful. I certainly wouldn't want that guy to work on any gas tank of mine. He's using a soldering iron, too hot and too low wattage. All of the plastic welders are at least several hundred watts and all of them have a temperature adjustment. I'm sure the job can be done with a soldering iron in a pinch but if the video is any indication the result is less than optimal.

Cheers,
Rob

Now there is a two part powder/liquid repair product which may be suitable. I have used it but not on petrol tanks. +1 on drilling at the ends of the crack. Get the area REALLY CLEAN before you start. Maybe use the 'groove' technique to get an extended bonding area..