Front tank sending unit.

Selahdoor

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Judging by this pic, there IS supposed to be quite a thick ring there. (# 10)

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Selahdoor

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One last pic tonight. When it turns black like that, the OSPHO has worked. It is sealed.
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chillman88

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Yep, I missed that this is a plastic tank, sorry!

I've never seen a tank without a seal between the sending unit and tank, so I suspected that was what the problem was right away. I wonder where you could track one down that size though...
 

Selahdoor

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I can find an o-ring to go under the sender plate. I could even cut a gasket from a piece of that old inner tube.

Then I need some sort of thick solid washer to go on top of it. A rubber o-ring or washer on top of the plate, and under that jar lid looking lock ring, will not hold the sending unit in place. It will deflect.

So I'll probably end up making something for that, myself. Maybe 2 or 3 rings made from an old plastic cutting board or something. Too bad I don't have a couple plastic pipes that are the right size, to cut rings out of. LOL I think I'll look into that!

I'll try putting it mostly together in the next day or two, (Raining here.) so I can take a pic and show what I mean by the gap. Well, if my camera will even take a pic that is good enough to show the problem. Man, I need a better camera.

I'd still like a recommendation from someone for some kind of sealant that will stand up to diesel fuel.
 

Brandon Roessner

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I am in the process of doing some similar fuel tank upgrades and was looking around for some diesel friendly sealants. I was considering trying this:


I also have the plastic front tank and will be working through some of the same problems you are experiencing. Good work and the info is very helpful, thanks.
 

TNBrett

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If you’re looking for a “caulk-like” sealant that will hold up to diesel fuel, the only thing I know of for sure is Poly Spec Thiokol 2235 or 2282. They are the “go to” in the industry for extreme chemical resistance. They are 2 component polysulfide caulks and rated for immersion service in diesel fuel. You will not like the price however, and you probably have to buy at least 1.5 gallons of it. See the chemical resistance guide here
There is a company called Boat Life that sells a a product called Life Calk. It’s a single component polysulfide, and is available in more “consumer oriented ” packaging. I didn’t however see any type of chemical resistance guide on their website. They did reference diesel resistance, but that’s not the same thing as being rated for immersion service.

I’m not sure how much help that is, but the question was asked.
 

chillman88

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Went to my local mom and pop auto parts place, looking for a good sealant that wouldn't break the bank.

I found this stuff. A little more spendy than the amazon price, but it looks like it will do the job.

https://www.amazon.com/Permatex-PermaShield-Resistant-Dressing-Sealant/dp/B01M164DO0/

Funny, it says comparable to Hylomar Universal Blue which I use on almost everything that gets a gasket.

I would have suggested it, but I figured you were looking for something a little more like an RTV type material.
 

Selahdoor

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Funny, it says comparable to Hylomar Universal Blue which I use on almost everything that gets a gasket.

I would have suggested it, but I figured you were looking for something a little more like an RTV type material.
Well, this stuff IS blue! LOL

It was pretty liquid when being applied, but thickened up pretty quickly. It was pretty much glue, in seconds. I'm betting it is providing a good seal.

Also, after I used a brush and brake cleaner to clean all the threads on the tank, and inside the 'lid', it did screw all the way on, and tight.


I decided to go ahead and coat the entire top of the sending unit with the epoxy.

You can see how this area forms a sort of bowl or container, in which dirt and water build up and sit. That was the reason for the extreme rust on the top of the sender unit. Even on the steel tank. But the 'bowl' effect is even worse here. Fortunately now, that water and dirt will just be sitting in an epoxy floored, and plastic walled, depression.

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Clb

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Reading thru pg 2
Hylomar does not set hard seals well as a gasket dressing, and is most all I use...

Edit I used to order it from England, the company now licenced permatex to make it here...
my old go to has always been av grade form a gasket.

hylomar was made by rolls royce, only thing sealing up my shovelhead!
now about this vent mod???
i have not looked into it yet so a few ???
Is this the roll over gizmo?
or is it the air escape plumbing?
what is the reason for the mod?
sorry for the lame questions to early not nuff Coffey
 
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Selahdoor

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I didn't do the vent mod. But it looks like you got the answer in the other thread. :)
 

Brandon Roessner

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Sorry this might be to late but would this fit close enough to work for rubber seal on the sending unit?

 

aggiediesel01

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Another known compatible RTV like sealant with Diesel and Diesel Oils is Motorcraft TA-31. Amazon will deliver it and sometimes the stealership stocks it and Oreilly's sometimes has it in their stores. It comes in a half size calk tube. Motorcraft says "A specially designed Alkoxy-Cure RTV Sealant for high temperature applications. Specifically recommended for use with the 7.3L Power Stroke." It's what International used to seal these engines during assembly. Looks very similar to "ultra Gray" from Permatex but I can't find any reference to Alkoxy-Cure in any of the Permatex literature.

 

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