41 pick up fuel tank sending unit
 

I have a 41 pickup. The fuel tank was leaking gas when it was full. I suspected the sending unit because the tank looked to be new. After quite a bit of aggravation, I finally got the tank out and found that it is a Drake tank which is why I had to disconnect the bed and raise it up to get the tank out out.

Now, I found that one of the sending unit screws was stripped and wouldn't
tighten enough to seal the tank. After trying to replace that screw, it simply stripped again. So, I replaced all 6 screws with 10-32 x 3/8" screws (they were only 1/4" to 9/32" long). I added an extra flat washer to take up the additional 1/16" of screw length. It has a cork sealing washer. It still leaked from around the sending unit seal. I suspect that the cork washer is shot.

Here's the question: Is the cork or the neoprene washer better? Also, is there a sealer that I can use as an additional sealing compound?

Thanks for your input.
Mike

Re: 41 pick up fuel tank sending unit
 

Can you tell if it is leaking from below the cork gasket or above the cork? Maybe weeping up the screw threads past the gasket? A bit of Permatex Blue sealant on the threads can help that.

Re: 41 pick up fuel tank sending unit
 

Jay: I can't really tell where it is leaking around the cork gasket. It seems to be all around it. The 10-32 threads in the tank are "blind" threads, there is no outlet. As such, there is no way that gas can be leaking thru the threaded holes.
I have to assume it is from all around the gasket.

Is Permatex Blue good as a "gasket" sealing compound and unaffected by gas?

Mike

Re: 41 pick up fuel tank sending unit
 

Mike, I prefer cork at that area.
The only RTV I know of that works with fuel is PERMATEX PERMASHIELD FUEL RESISTANT GASKET DRESSING & FLANGE SEALANT. It is orange in color. Autozone had it as did Napa.
The blue stuff will quickly turn to mush.

Re: 41 pick up fuel tank sending unit
 

I once called Permatex tech support to ask that exact question. Was told Blue is unaffected by gasoline, can be used in the presence of gas.

But I'm still wondering why the gasket is not doing its job? If you use sealing compound, what problem in the future getting the sender off, possibly pieces of gasket/sealant getting into the tank? I don't know if you should use a sealant. Let's see what others have to say.

Edit: After reading Kube's response above, I would trust his deep experience over what I was told by the Permatex help desk.

Re: 41 pick up fuel tank sending unit
 

it probably is leaking where the "attaching ring" is soldered to the tank, caused by too long of screw which actually raised the ring off the tank, you can fix this by sealing with jb weld or maybe the permatex sealandt that Kube recommends

Re: 41 pick up fuel tank sending unit
 

Hmmm... I didn't think of that. Definitely something that needs to be inspected carefully.

Re: 41 pick up fuel tank sending unit
 

Seal-All is a good fuel resistant sealant.

Re: 41 pick up fuel tank sending unit
 

Try using 2 cork gaskets instead of 1.

Re: 41 pick up fuel tank sending unit
 

Grrr. After replying, I found that I had "timed out" when I went to post my reply.

I'm not going thru that again.

I'll try Kube's recommendation first. If that fails, I'll post the results and see what other options I have. If it succeeds, I'll let you know.

Mike

Re: 41 pick up fuel tank sending unit
 

So, I found the problem to my gas tank leaking around the sending unit.

It didn't have anything to do with the tank.
It was the sending unit itself. The mounting flange must not have been centered correctly when it was "Stamped". One side of the mounting flange had a lip of 0.085" while the opposing side was only 0.020". As a result, the side that was at 0.085" would never have sealed with the 0.062 cork gasket.

I bought some cork gasket material and found the flange issue while making a new gasket. Everything is together and I am letting it sit until tomorrow. Then, I'll refill the tank and see if my repair sanding worked. I had sanded the flange lip that was at 0.085" down to about 0.050". Then the 0.062 gasket material should seal. I also used the Permatex Permashield that Kube had recommended. Although it is blue and not orange. I hadn't noticed the color difference until I reread Kube's commentary. The tube it came in was orange and I hadn't thought anything about it until I went to use it today. The only thing that seems different is the stuff I bought at AutoZone is number 85420. Otherwise it is the same as what Kube had recommended. We'll see how things go and I will update.

Mike

Re: 41 pick up fuel tank sending unit
 

Mike, You will be fine with the sealer you'd purchased. I have my favorite but the one you chose appears to work well with fuels.

Good catch on the flange.

Re: 41 pick up fuel tank sending unit
 

I happened to think of this after posting my last message.

This flange issue isn't strictly on '41 pickup. I could happen on almost any sending unit.

If you are replacing your sending unit, look closely at the lip of the mounting flange. It could be defective and should be replaced by your vendor. Otherwise, you'll leak gas like I did. I assume that my sending unit was not the original and had been replaced, probably a couple of times.

Mike

Re: 41 pick up fuel tank sending unit
 

Re: 41 pick up fuel tank sending unit
 

Well, the fix on the sending unit worked. After putting everything back together I filled the tank and had no leaks. Saturday and today I remounted the tank into the truck, lowered the box back down. I then re-attached everything. I'm not overly pleased with the filler neck to tank hose. It seems a bit tight fitting it in and thru the box cutout. I'll have to keep a close eye on it.

So, now I'll have to give it the ultimate test and fill the tank. Hopefully all will work out. As long as I had the truck on my 4 post, I drained the oil and will refill with new. There are a few other issues that need to be cleared up, but I'm looking for a test run this week.

Thanks for all the help. I'll be looking for more assistance when winter comes and I look at the "winter projects".

Mike