The Stovebolt Site Forums The Parking Lot Big Bolts Need help with vacuum wiper fitting size . . .

Hello fellow Big Bolters . . . . placed this question in general discussion but am still stymied . . . and having trouble getting photos to show. Hope it shows this time?

My issue: I have replaced the vacuum wiper motor with a 6v electric motor. The thru firewall valve, the 2 ton rear end vacuum control mechanism (1947-1954 Truck Factory Assembly Manual .. Section 5 .. Page 7.00 .. upper left corner) shows a part #3682936 Connector which is an elbow into which a small brass tube is threaded and then the rubber tubing to the wiper motor slides onto that brass tube. While working on a cut down section of that brass tube to use as a plug, it was thrown from my fingers by the wire brush and landed somewhere in that place in the garage where all things small, which are needed, cannot be found!

In essence, I need to find the size of that small brass tube threading so I can plug the hole. It is not a 1/8" npt fitting, tried that. It's smaller. The opening in the elbow shows to be .216" but I cannot get a thread gauge into the hole. The pipe is somewhere between 1/8"npt and a 12-24 screw diameter?!

I'm getting very close to firing up old May-Belle and this open vacuum line is about my last issue. Any help would be greatly appreciated. I would imagine I'm not the only one to have eliminated the wiper vacuum line from a 1951 2-ton model 6100 Chevy truck?

Thanks in advance for your help,
stumpy in Austin

Your thread in GTT has been deleted. Stovebolt.com frowns on posting the same question in multiple forums.

Well, no one in the general truck knew an answer because (apparently) only the Big Bolts have the vacuum control valve?! I hope to receive an answer here!

And just to mention, posting photos is a beach . . . the site gives an outrageously long answer which depends on a video which is not available . . . and then I find an attachment method which is not even mentioned in the how to post photos?!

As in many things I find lately . . . it doesn't have to be this difficult!!

Have you tried a brake line fitting...looks like it's a flare fitting to me. My trucks have a 1/8" npt on the inside side of the check valve...looks like you have a 90* fitting attached to the check valve that converts it to flare.

The reason the general truck guys weren't able to help is the small trucks don't have the vacuum check valve on their firewalls, their wiper vacuum line just goes through a grommet.

To post pictures I do the following;

Click on "Use Full Editor" in the post/reply box.

Then scroll down and and click on "Attachment Manager" in the Post Options section.

Then split your monitor screen with Stovebolt open on one side and your photo file open on the other side.

Click on the photo you want and Drag and Drop the picture over to the Stovebolt side and your done (as long as it's not over sized)!

Hope this helps,

Mike B

Hy 51 2 Ton, what I think I am looking at in your picture is an inverted flare elbow, probably 3/16" tube, but it might be 1/4" tube. I am not sure that they make a "plug" for that fitting, but if you go to your parts store and buy a 3/16" inverted flare nut and a 1/4" inverted flare nut I think one if them should thread into your elbow. I'll look in my books and see if I can find a "plug" in either of those sizes. Okay, the Weatherhead part number for the inverted flare plugs are, 3/16" 131X3, 1/4" 131X4, hope that helps.

Thanks Mike B . . I have tried a 1/8" npt plug and it was too large. The plug measures .320" just below the first thread, so it's much larger. I just thought to try a 1/4-28 bolt and it was also too large. My measurements with a caliper have been between .208 and .212" inside the elbow but it is difficult with the new plastic/insulated firewall liner to even get in there for a measurement.

Thanks 3B . . Although it was about a year ago that I took out the brass tubing, I remember it being straight (or npt) threading, no flare? If only the wire wheel hadn't flung the little piece into oblivion!! I will look up the part numbers for the flare plugs and see what I can order. Many thanks for your finding that info.

Always appreciate the knowledge base here with the Big Bolters!!

Not sure if these will help any but was able to get a light & phone under the dash for a closer pic . . .

Since the outside of the 90d street ell is square and it looks like there is a flare down in there and the hole measures .208 to .212 . . . I'm hoping a 3/16" flare plug will work?!

Wish me luck . . and THANKS guys!!

Have you thought about removing the brass fitting from the check valve and then just plugging that hole or soldering the 90* fitting closed and putting it back in as the plug?

Mike B

Just this afternoon . . . after seeing that the 3/16" weatherhead plug is a 3/8-24 thread . . . I had decided to try to remove the brass 90d ell. Looks like the only alternative at this point. Hope I can get the little booger out of there without any more issues. Will certainly be easier to find a plug or seal it up or retap for a bolt & sealing washer??

Tomorrow is another day . . . today I received my new side glass and setting tape, only to find the tape to be twice the thickness needed for the glass sent! Geeze, ain't nothing simple?!

In the past couple decades my personal mantra has become . . . It just doesn't have to be this difficult!! Seems, yet again, I'm wrong.

Oh, how things look so different in the morning after a good nights sleep rather than in an afternoon after numerous frustrating little issues.

I was able to remove the brass elbow and, low & behold, the 1/8 npt plug fit right into the the valve body. It turned out that once I had the elbow out and away from the firewall interior cover and could easily try . . a 1/4-28 bolt threaded easily into the elbow. As I had recalled, the brass tube was a straight thread. Obviously, now that I have the plug installed, the small piece lost earlier will be found on the floor next to the lathe foot or against the drill press base or . . .??!!

Appreciate your responses guys and wish you the best in your Big Bolt redo, rework, restore projects!!

Cheers,
stumpy in Austin

Glad to hear it all worked out and you can now move on to the next task!

Mike B