Thoughts on the source of the leak?

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Model T Ford Forum: Forum 2016: Thoughts on the source of the leak?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie Dill in Stamford, CT on Friday, December 09, 2016 - 09:54 am:

Fuel bulb beneath gas tank has a slow leak. I can't tell where it's coming from. I'm planning on doing some more troubleshooting, but before I do too much, are there places where I might "expect" a leak?

It doesn't appear to be petcock because the bulb above that has fuel on it.




Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Friday, December 09, 2016 - 10:01 am:

Might be the threads where the bulb fits into the bottom of the gas tank.

If you decide to drain the tank and remove the bulb to seal the threads, proceed with caution - those things are usually stuck tight and you run the risk of damaging the tank or snapping off the bulb if you apply too much force.

If you are successful at removing the bulb, clean the threads on the bulb and tank and use the sealer of your choice. Some have said that regular teflon tape gets attacked by gasoline, but I have had good luck with it so far.

Supposedly there is a "yellow" teflon tape that is impervious to gasoline.

If you use tape, be careful not to leave any threads of tape exposed on the fuel side, where they might eventually break off and clog the line or carburetor. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie Dill in Stamford, CT on Friday, December 09, 2016 - 11:11 am:

Sounds scary (the breaking off part). I'm going to try to get a nice photo of the connection to the tank. I'm hopeful that it's not there. I would hope, but doubt that it's where the bulb exits to the fuel line. That would be too easy. Another worry of mine is that it's with the petcock between the tank and the bulb. Maybe a seal there is bad.

I will investigate further but suspect that the best solution is to turn off the fuel between use and put a pan beneath it. It's a very slow leak. But it also is enough so that the smell of gasoline is constant in the garage.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Friday, December 09, 2016 - 11:14 am:

Generally the leaks are around the small lever that opens and closes the gas flow.

Remove the bulb and rebuild it. The lever is held with small coil spring, you sometimes have to replace that spring, hardware stores are a place to find a replacement.

At times the brass lever has to be 'lapped' in to give good fit of the taper section in the iron bowl. Use lapping compound or TimeSaver.

Then a new lead washer seal at the large nut of the gas outlet is used too. Other than the threads at the tank end or the petcock threads, those pesky seeps are controlled with paste fuel sealer or proper gas-resistant tape.







After rebuild, test the sediment bulb by closing the petcock, capping off the outlet, opening the lever so gas is allowed out of the bulb, and fill the bulb with gas to the top of the bulb so you see a small meniscus of gas pooling there.

Then suspend in a coffee can, and wait. There should be no more weeps anywhere, and the pool of gas at the top of the bulb should remain.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Friday, December 09, 2016 - 11:26 am:

The Model T has an "OPEN" fuel system so there will be the smell of gas. If there was a leak at the joint between the sediment bulb and tank there would be signs on the bottom of the tank around the bulb (wet or staining). I can't see any signs of leak in the photos, no drips hanging off the pack nut or end of petcock. If the whole bulb is damp, it could be the lead washer that seals the screen assembly to the body.
Unless you have another shut off at the carb, it's a good idea, the fuel should be shut off at the bulb when the car is not in regular use. The bulb looks to have been off the car in recent past so might not be that hard to remove.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham on Friday, December 09, 2016 - 11:30 am:

Dan, I think you covered all the bases ! The Model T sediment bulb can leak:
1. at the tank
2. at the shut-off
3. at the screen/outlet
4. at the drain petcock

Questions for you, how "fine" is "Timesaver" ?? On other similar items, I found a lapping compound coarser than, say, fine rubbing compound would work until the "grittiness" wore away in use, or, sometimes, would bind the shutoff so it couldn't be moved.

What is paste fuel sealer ? Is that the yellow stuff showing at the shutoff in your photo ? Trade name ? Where do you get it ?

Test method looks good, "in the old days" we'd close everything off, suck hard on the inlet opening, and if your cheeks stuck to your teeth, you're good to go ! ; >)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Friday, December 09, 2016 - 11:41 am:

RE; how "fine" is "Timesaver"; very fine indeed! :-) People have in the past suggested using tooth paste to lap the valve in. The yellow stuff is the Timesaver.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Burger in Spokane on Friday, December 09, 2016 - 12:12 pm:

Dan,

I would buy you a beer just for using the word "meniscus".

Put another star on your crown, Amigo ! :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Barker - Dayton, OH on Friday, December 09, 2016 - 04:45 pm:

Rich - Permatex makes a fuel rated sealant. This is what I use and have had no problems and no leaks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham on Friday, December 09, 2016 - 05:13 pm:

Mark, Dave, thanks for the replies, I'm in need of "updating" !!
Dave, I think the permatex product would be preferable to thread sealing tapes . . .


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie Dill in Stamford, CT on Friday, December 09, 2016 - 06:23 pm:

I did a very thorough clean off of the bulb today. All around, and all the way to the bottom of the tank. Used a little lacquer thinner as well. My hope is that there's nothing there tomorrow, or if there is, I'll be able to see where it's coming from.

Worst case, it's a VERY slow leak. I'm going to get the car put back together and running first, then might take on the fuel bulb issue after that.

Bottom's up. Today I re-attached the oil pan inspection plate, cleaned out the head bolt threads. Pretty confident I'm ready to reinstall the head. Once that's done I think I can fire her up and see what happens.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Friday, December 09, 2016 - 10:02 pm:

Charlie, what seems a small leak can be much more. The gas evaporates as it escapes, hence the smell. If things are wet, you have more than a slow leak.

Hope this helps.
Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham on Friday, December 09, 2016 - 10:09 pm:

Heck, a model T just ain't normal if it ain't leakin' - still, gas leaks are a little more worrisome than water and oil. I have the same thing going on, Charlie, that's why I'm paying close attention here ! PS - that gasoline smell is why the Indians called 'em "skunk wagons" !! ; > )


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charles Weisgerber- Vancouver WA. on Friday, December 09, 2016 - 10:39 pm:

Charlie, I had the same problem with my sediment bowl. I ended up taking the bowl off and doing a simple rebuild.

Took it all apart and cleaned everything.

Lapped the main shut-off valve and drain petcock valve surfaces with Time Saver (yellow)

Installed a new filter screen, as mine had a big hole in it.

Installed new lead gasket

Sealed all threaded areas on assembly.

I did this about a year and a half ago and everything is still dry.


Top of pagePrevious messageNext messageBottom of page Link to this message  By keith g barrier Savannah Tn. on Saturday, December 10, 2016 - 06:15 am:

With cast iron it is possible to have a porous casting, just a thought. KGB


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie Dill in Stamford, CT on Saturday, December 10, 2016 - 09:15 am:

I'm enjoying the various projects I'm undertaking on my Model T. Learning a ton. I'm sure at some point in the next month or two, I'll drain the tank and do a rebuild. I'll have to read up on lapping. Not something I'm familiar with - sounds like it's basically a resurfacing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Corey Walker, Brownsboro TX on Saturday, December 10, 2016 - 12:11 pm:

Just a suggestion, I'd clean that tank now. If there is anything in there it's going to end up in that sediment bowl and you'll have to take it apart again to get it out. I bought a tank on eBay, cleaned it out and drove fine for a long time. One day I guess the ethanol broke more stuff loose. I had to drive about 3 miles home in low because of fuel starvation. I removed the sediment bowl and it was full of stuff, sediment I guess. I took the tank off, screwed an old spark plug in the bottom, filled it part way with vinegar, water and B.B.'s, tied it on the back of my truck for a while and drove around. I probably should have used some sealer or something but I haven't had any more problems.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Sunday, December 11, 2016 - 11:03 pm:

Not sure you all have the luxury of an air supply but since my shop has half inch black iron pipe air supply with quick disconnects I just made up a test fixture out of some odd pipe fittings and a male air quick connect fittings so I could then screw the sediment bowl assembly into the female end of a standard 1/2" pipe union that I could then plug into my air supply at a regulator tap point. I took a piece of scrap gas line and crimped it flat and soldered it shut for good measure and then set the regulator for a pretty low air pressure and simply squirted soapy water all over the sediment assembly and started looking for bubbles. I found all of the leaks both big and small and then only had two possible places after that which was the 1/2" pipe thread fitting of the sediment bulb into the tank bottom and the gas line which is very easy to seal using a short piece of neoprene hose instead of the ferrule so that the hose crush seals the gas line super snug yet lets it move a bit which keeps it from breaking. The regulated air supply keeps things under control and when you don't have any more bubbles the leaks are fixed. I also found that it works best to check the main sediment shut off lever at 2 positions (on and off). If you prefer you can also put an air hose between the main supply and the shutoff sediment bulb being tested and place the whole thing into a bucket of water and look for bubbles that way. If you use too high of a pressure you will force leaks in places that the liquid will not leak but using air shows you all of the leaks that you have and where they are in short order.

I have also used a similar setup to look for intake manifold leaks in an aluminum intake that had some holes welded up.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed in California on Monday, December 12, 2016 - 07:09 am:

Put some fuel system leak detecting dye in the tank, use a black light to find the leak.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie Dill in Stamford, CT on Monday, December 12, 2016 - 07:39 am:

I took a close look yesterday after having wiped it clean and dry. No leak coming from tank to bulb connection. Appears to be coming from the level of the shut off valve. Can't say which side. I think there is some capillary action moving the fuel sideways in that area.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan B on Monday, December 12, 2016 - 09:14 am:

Charlie,

Once you figure out the source of your leak and are able to repair it, consider using EZ Turn fuel lube on the threaded and valve surfaces.. It is the absolute best product for this application.

Over the summer I did a complete overhaul of the fuel system and used it on all the fittings upon reassembly. Months later, it remains bone dry and the best part is that the fuel shutoff handle at the sediment bulb and on the shutoff I installed at the carb are much easier to turn.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Monday, December 12, 2016 - 09:18 am:

Charlie

That is where the weeps develop, at the taper shut off. Have found a good method of closing, when you have a known good shut off that you lapped in and it works well with a new spring to hold it in position.

After opening or closing the little lever, give the end of the lever, in-line with the valve, a small 'tap' with a little hammer or tool, to 'set' the shut off valve inside the iron bulb.

That usually stops any weeps, but still allows the valve to open or close again when needed.

This method works on any type petcock valve too, like the oil cocks and radiator cock.


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