Plastic safe, diesel resistant thread sealant needed

[BlakeB]

I have a Massey Ferguson tractor with a plastic fuel tank that needs a new fuel hose fitting. We have had trouble with this plastic threaded fitting leaking around the threads in the past. What thread sealant would hold up to the diesel fuel and not harm the plastic fuel tank?

 

[BlakeB]

I have permatex high temp thread sealant, permatex Indian head gasket shellac compound and permatex form a gasket sealant #2 (non-hardening). Not sure if any of those will work, but that's what I already have.

 

[Linctex]

THE ONLY THING that will work is Permatex 14 thread sealant with Teflon

This stuff:

https://shop.advanceautoparts.com/p/permatex-thread-sealant-with-ptfe-1-oz-80631/16160028-p

 

[Trav]

THIS Is what you want.

 

[pbm]

Last week I posted a thread about the stripped drain plug on my Corolla's A/T pan.
There is no oversize plug for the M10x150 plug so I was looking at either tapping it out or buying a new pan.
I was fortunate that a new bolt of the same size (but longer) threaded in but found a few drops of ATF underneath the car after every drive.....I ended up using Permatex #2 (non-hardening) on the base of the bolt and washer and no more leaks....I let it set up overnight before driving the car.

 

[Trav]

Diesel fuel is a different animal, it seem to seep through almost anything. Hylomar was developed by RR to seal components that carried jet fuel which is almost the same. I used it on a leaking and broken furnace oil pump pressure gasket in an dire emergency 4 years ago and it has not leaked a drop.
I have a gasket but decided to wait till it dripped again just to see how long it will last.

 

[doitmyself]

So many choices! I think that dealing with plastic is as important to consider along with the difficulty of diesel fuel. The Permatex #2 data sheet does NOT mention plastic use.

What about teflon tape?

Trav's Hylomar M seems well regarded. On metal fuel tank joints I use Gasoila: https://www.gasoila.com/products/pipe-thread-sealants/gasoila-soft-set-thread-sealant-with-ptfe.html I have no experience with it on plastic. It's the only product I see the fuel trades people using around me.

 

[Cujet]

Originally Posted by doitmyself


What about teflon tape?


Teflon tape is not a good choice with any type of fuels. It's likely to deteriorate enough to put small particulates into the fuel. While I can't predict what will happen, the results can be near catastrophic if a piece gets into a small passageway or mechanism. Nor does T tape seal fuels well.

Clearly, if one applies teflon tape to the later threads on a fitting, particulates are not likely to go downstream. But why take the chance?

Loctite makes anaerobic thread sealants specifically for such applications.

The Permatex 14 thread sealant is similar/same as the Loctite products. (Note: there is a bit of overlap in Permatex/Loctite products. Here is a cross reference chart: https://www.permatex.com/contact/cross-reference/ )

Loctite 592 or 577 is a good choice for diesel fuel, with a relatively soft bond, and are fantastic sealants.

 

[BlakeB]

I sent Permatex an email, I'll see what they say and go from there. Thanks for the suggestions!

 

[andyd]

Permatex Form-A-Gasket No. 2 Sealant (3 oz.) Pretty much the same as Hylomar , less expensive and widely available . Let us know what Permatex says please TIA

 

[BlakeB]

From Permatex:

 

[Trav]

Originally Posted by andyd

Permatex Form-A-Gasket No. 2 Sealant (3 oz.) Pretty much the same as Hylomar , less expensive and widely available . Let us know what Permatex says please TIA

No, its not even close to Hylomar.
Quote
Hylomar Universal Blue enables the effective sealing of metal to metal and plastic to plastic


Hylomar PDF

 

[BlakeB]

Originally Posted by Trav
Originally Posted by andyd

Permatex Form-A-Gasket No. 2 Sealant (3 oz.) Pretty much the same as Hylomar , less expensive and widely available . Let us know what Permatex says please TIA

No, its not even close to Hylomar.
Quote
Hylomar Universal Blue enables the effective sealing of metal to metal and plastic to plastic


Hylomar PDF

Do you think the Permatex equivalent would work? It's locally available and I was hoping to get this done tomorrow.
Permatex Hylomar

 

[DallasTexas]

Hylomar Universal Blue is what I use on my Mercedes pencil type glow plugs as they tend to build up carbon. I took them out to replace and they came out clean and the Hylomar gooped on them were still tacky. Great stuff, having said that I have not used Permatex non hardening product.

 

[Trav]

I never used it but it was originally made under license by Permatex so I assume it would probably work okay.

 

[doitmyself]

I would be concerned that the Permashield only mentions that it is good for metal parts. No mention of plastic use anywhere in it's tech. sheet. And, Permatex replied with a comment that they have no product for diesel and plastic.

 

[BlakeB]

I found this and I think it might work, the fuel line fitting does have a flange on it, from the from the factory they use a rubber gasket/o-ring between the tank and fitting. The gasket/o-ring is no longer available and they say to use a locktite sealant. (MS 9220). To get a tube of the OEM specified sealant here is over $100. If you guys don't think this will work, I'll probably just order the hylomar and try it.

DAP RTV

 

[nthach]

Typically, sealant is not recommend for plastic threads, I've used Permatex #1 in a pinch before and it held until the car was scrapped.

Maybe a Teflon-rich pipe dope like these:
https://www.oatey.com/2371984/Product/Oatey-Great-White-Pipe-Joint-Compound-With-PTFE
https://www.rectorseal.com/rectorseal-t-plus-2/

 

[Fsharp]

You've already got the shellac, which works great on threads and says diesel resistant right on the bottle. I'd use that And just make sure to let it set up for a day or so before filling with diesel.

 

[NYEngineer]

I've been around diesel engines for a LONG time. Might I suggest seeing if that same fitting is available in brass so you're only dealing with the plastic tank.

I've used the Loctite teflon sealant with good success on all sorts of materials. Teflon tape has also worked. I've used Block with great success on iron and aluminum but cannot remember if I've ever used it on plastic. The trick with Block is to install it and let it set up before subjecting it to fuel.