Petrol proof adhesives etc

[wombat88]

Is there any adhesive, sealant or tape that can be relied upon to be petrol proof?

OK so this is not for a boat but a car that has a split in a petrol tank breather expansion tank...a part that is no longer available.

 

[thinwater]

The obvious answer is to suggest a repair kit from the autoparts place. In the US Permatex is a leading brand.

It will almost certainly be epoxy-based. But not quite the same as boat laminating epoxy.

The other options is plastic welding. But I don't know the plastic type. You could experiment on a corner of a mounting flange.

We also don't know why it cracked. If it is age and repeated flexing due to pressure cycling, I would not hold out high hopes.

 

[Stemar]

It would depend on what the tank is made of, AFAIK, polyethylene/polypropylene can't be glued, but can be welded with a soldering iron. For metal, I'd be temped to patch it with glass cloth and epoxy. After all, there are plenty of GRP fuel tanks on boats, so it should work

 

[VicS]

Is there any adhesive, sealant or tape that can be relied upon to be petrol proof?

OK so this is not for a boat but a car that has a split in a petrol tank breather expansion tank...a part that is no longer available.

A polyurethane sealant such as Terostat PU92 fuel resistant adhesive/mastic,

but as indicated above it is unlikely to adhere to polyethylene or polypropylene

.

 

[wombat88]

A little extra info.

It is over forty years old. It is made of a hard, shiny, black plastic. It is cracked where one of the pipes enters.

After years of exposure to petrol I am somewhat reluctant to use a naked flame but maybe melting it with a soldering iron might do the trick if there is no obvious adhesive.

 

[Draystone]

CT1

 

[penberth3]

A little extra info.

It is over forty years old. It is made of a hard, shiny, black plastic. It is cracked where one of the pipes enters.

After years of exposure to petrol I am somewhat reluctant to use a naked flame but maybe melting it with a soldering iron might do the trick if there is no obvious adhesive.

You can try, but the problem is aged/oxidised material and contamination.

Others have already suggsted Epoxy resin, I've been told in the past this is petrol resistant. I'd try patching over the outside, but it needs sorting, petrol leaks aren't a good thing!

 

[rogerthebodger]

hard, shiny, black plastic could be a thermosetting plastic. Examples of thermosetting plastics include bakelite, urea-formaldehyde resins.

these types of plastic cannot be heat welded.

The other type are thermoplastics that can be heat welded like polyurethane polypropylene even PVC

 

[penberth3]

hard, shiny, black plastic could be a thermosetting plastic. Examples of thermosetting plastics include bakelite, urea-formaldehyde resins.

these types of plastic cannot be heat welded.....

Very unlikely on a vehicle fuel tank system. Probably HDPE.

 

[rogerthebodger]

Very unlikely on a vehicle fuel tank system. Probably HDPE.

If that's the case welding is the only way to fix it as I did with HDPE mooring floats for one of my moorings

Most adhesive will not stick to HDPE

This is the type of plastic welder i use

 

[penberth3]

If that's the case welding is the only way to fix it as I did with HDPE mooring floats for one of my moorings

Welding isn't the only way. Read my Post #7. I would hesitate to use a hot air gun anywhere near a fuel system.

 

[rogerthebodger]

I tried to use epoxy but it just peels off in short time.

That's when I purchased a plastic welder

I have had other items (engine drip tray ) made from HDPE and all of them were welded.

take your point about welding a petrol tank but fill it with water of an inert gas before welding.

Another way id to cur the pipe off and replace it with a bulkhead fitting o a small skin fitting

 

[Stemar]

Just a thought - how big is it? Could you use something else in its place - a washer bottle, for example, or even a 1 or 2l polyprop bottle, held in place by a big jubilee clip?

 

[penberth3]

Just a thought - how big is it? Could you use something else in its place - a washer bottle, for example, or even a 1 or 2l polyprop bottle, held in place by a big jubilee clip?

Or do without it altogether. By-pass, remove, blank off. Surely it's only needed when the tank is full to the brim, which can be avoided.

 

[wombat88]

Or do without it altogether. By-pass, remove, blank off. Surely it's only needed when the tank is full to the brim, which can be avoided.

sorely tempted...

 

[Stemar]

Or do without it altogether. By-pass, remove, blank off. Surely it's only needed when the tank is full to the brim, which can be avoided.

You'll need some sort of breather, though, or you'll put your foot down do get out of a developing nasty and the engine will fade. There always used to be a breather hole in the filler. Have they stopped doing that now?

 

[thinwater]

You'll need some sort of breather, though, or you'll put your foot down do get out of a developing nasty and the engine will fade. There always used to be a breather hole in the filler. Have they stopped doing that now?

Obviously. Vapor control / evaporative emissions. Unless you fully understand the functioning the of the system it would be dangerous to change it, and it sounds like we don't. Controls started in the mid-70s, so this would be one of the earlier versions, but does not pre-date them.