MotoSeal Diesel resistant RTV?

[Cubey]

Has anybody used Permatex MotoSeal 1 on something where it was exposed to diesel? It claims to resist fuels:

https://www.oreillyauto.com/detail/...otoseal-1-ultimate-gasket-maker/29132/4610369

My fuel selector valve was sure enough seeping out from the seam on the outer side (away from the frame) at the little clip. The remaining fuel inside was seeping out by gravity when I turned it over. Not sure why it leaked so badly when set to the rear tank unless it was also a leaking hose, unless in the rear position the two halfs were put under more stress casing a bigger leak, which is possible I suppose. I'm wondering if it was just a couple of weak rivets not quite clamping the two halves together.

I drilled out the 4 rivets, but today I can't get any #6 machine screws to replace them with, both hardware stores here are closed Sundays. (Really??) Neither O'Reilly nor AutoZone had any that small. So, I will go get those tomorrow. At least it's very nice weather so I've been going on foot.

My fuel line is still bypassing the valve so I can still drive it with the valve off, but I'm lacking a working fuel gauge. If I knew the pinout, I could put a jumper wire in it, but hopefully I will have this put back together tomorrow so it won't matter.

I willtry to remember to take some pictures tomorrow and make a separate thread about taking it apart, since there seems to be NO info on it online for this style valve. I did see one on another forum for the style with the clips, but mine just has hose barns and you use normal hose clamps, no clips. You have to be careful of some thin brass parts and 2 springs in the "*******" style valve I have when you put it back together. You also have to be sure not to spin the part that the motor connects to for the valves. As long as you are very careful, it's easy to avoid.

 

[dgr]

I wouldn't use silicone where there is fuel or where there are small ports or other things to get clogged with the squeeze out. I'd try permatex #2.

 

[Cubey]

I wouldn't use silicone where there is fuel or where there are small ports or other things to get clogged with the squeeze out. I'd try permatex #2.

Do you basically apply it the same way? I have very little experience with these products. I wont need very much of whatever I use, I just want to seal up between the two plastic halves.

Here it is all cleaned up, with the rivets removed, so the gap between the halves is large right now. The clips make this very easy, since you can line everything up, clip it together and have it stay while you get the screws/nuts ready to clamp it down together. The leak was on this front side at the clip.

I use a cut off strip of an old credit card doubled over in half to slip under the clips to raise them up without too much force. It works great for getting it apart.

I'll take disassembled and internal pics tomorrow when I have it taken apart again for sealing. I don't want to taking it apart repeatedly unless it's necessary.

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[dgr]

That looks like glass reinforced plastic? I would expect to find a formed o-ring in the halves. I'm really not sure the best way to deal with that.

I'm really not sure what gasket sealant to use with plastics. I think that permatex #2 would be safe to use. It has an alcohol solvent. It applies like any gasket maker. Just a thin coat.

 

[chillman88]

I don't believe you should have any fuel in that spot anyway. If you do I'd imagine the o-rings in the valve itself are probably leaking?

 

[Cubey]

Doing some in depth studying of F-series schematics (E-series are impossible to find) I think it's safe to say that I know the pin-out, if sealing this fails and I decide to go with a new one later.

For reference to others in the future who may be as lost as I was, here the pinout/wire colors as far as I have researched, at least according to my 85 E350. The sending unit and cluster wires are what are different on E-series, not the power/ground from the switch.

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The hard part for wiring in a new Pollak valve is knowing which way to wire in the brown/red. Get them backwards and you'll get the engine pulling from one tank but showing the gauge for the other. If the gauge hasn't dropped after 100 miles but does when you switch tanks, then I guess you would know it's backwards. Well, I suppose you could check it by just plugging it in, turning the key, and flipping the tank selector switch, and seeing which passages you can blow air through based on the switch's position.

 

[Cubey]

I don't believe you should have any fuel in that spot anyway. If you do I'd imagine the o-rings in the valve itself are probably leaking?

So it's not supposed to be filled with fuel down in the electrical part?
I guess I should have guessed that.

Well no harm done. I will crawl back under and cap off the front tank's lines with bolts and hose clamps to keep crap out for now. I'll see about buying a new one online later after I get to Arizona.

What's curious about the new ones is they tell you to put in line fuel filters between your tanks and the valve. Maybe that's what helps kill them, picking up rust and dirt. http://products.pollakaftermarket.com/Asset/42-159 IS_41-revdd.pdf

The cheap Mr Gasket electric pump on my F250 that was on it when I got it, a lot of people complain that they die fast. Well, somebody put a cheap in line filter before it, which might be the key to keeping it alive as long as it has been on my truck.

Well at least I got something good out of messing with this old valve, I figured out how to wire a new one. That's bloody hard to figure out on these old valves, My Bronco/F-series Haynes manual barely mentions these valves other than to say they are "early". All the in depth info it shows is only for the clip connection style (like my F250 has).

But it appears the factory pigtail pinout is identical on both style of valves. It would be nice if they bothered to TELL YOU THAT though!

 

[Cubey]

I don't believe you should have any fuel in that spot anyway. If you do I'd imagine the o-rings in the valve itself are probably leaking?

I took it apart further and found that the two large, black, square cut o-rings on the supply side are excessively large and aren't sealing well anymore. Return side seems fine, the o-rings don't have that problem, but could probably stand to be replaced too. The small blue o-rings all seem in really good shape, not dried out like the black ones.

In fact it doesn't even wanna go back together with the stretched out ones. Not a big deal for getting down the road, i can either plug it back in as-is to enable my fuel gauge, or I can put a jumper wire at the harness for the gauge/sending unit. Fuel lines are already bypassing the valve itself.

How hard is it to find square cut o-rings like that, if you happen to know?

I guess I will take a walk over to the hardware store after all tomorrow and see if they have some o-rings that might work. I will take the valve head in it's taken apart state with me to check sizes. It seems to be about a 9/16" ID and 11/16" OD o-ring. Rounded ones might work too since that plastic bit doesn't move.

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[dgr]

McMaster will send you 100 for $7-12 depending on what material you want. What to do with 98 o-rings...?

 

[chillman88]

Figure out what the size is called, for example our return lines use size "-111"

Once you have that, a search on Amazon might net you a package of 25 instead of 100. At least you won't be junking as many.

EDIT: Not square but only $10 for 10. Worst case you're only out $10 which isn't too bad lol
https://www.amazon.com/dp/B000FMUW8S/ref=cm_sw_r_cp_awdb_t1_LHnaEbZFZWXKK

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[typ4]

Moto seal has no use anywhere on our trucks. And it will not be happy in fuel.
Use anerobic if you need some sealant.