Topic: leaking petcock


fordmerc    -- 01-21-2018 @ 11:09 AM
  radiator drain petcock leaks - slowly - maybe 2 ml. a day or less. I removed it and polished the inner surfaces with polishing compound, to no avail.
Testing: air bubbles leak out at around 3 psi pressure!
Yes, I know the system isn't pressurized, and it leaks with the car just sitting there.
Any suggestions for a fix? My petcock is not reproduced; available replacements just won't look right.


trjford8    -- 01-21-2018 @ 11:26 AM
  Are the air bubbles coming out around the threads where it screws into the radiator or leaking around the center shaft.


fordmerc    -- 01-21-2018 @ 12:55 PM
  air bubbles from around the center shaft at both top and bottom -unfortunately


supereal    -- 01-21-2018 @ 1:36 PM
  C&G shows the proper petcock as 48-8115. The are not cheap at about $25.You can see it in the online catalog www.cgfordparts.com They work on a taper tensioned by a spring on the end of the shaft. You may be able to stop the leak by installing a stronger spring after removing the cotter pin on the shaft. If that doesn't work, a dose of Barr's Leakes will do it. Anti freeze lowers the surface tension of the coolant allowing leaks.


fordmerc    -- 01-21-2018 @ 2:38 PM
  I have been unable to find "40-8115" which the Ford Chassis Parts manual says is appropriate for my car. Unfortunately, the body of "48-8115" does not look like mine. If all else fails I can install the latter. My petcock operates as you describe and at reassembly after polishing surfaces it seemed to have a pretty strong spring, but I will try to find a stronger spring. I'll also try Barr's Leaks.


Drbrown    -- 01-21-2018 @ 9:45 PM
  Can you post a photo ? I have several 1930-1940 vintage my Dad saved.


40 Coupe    -- 01-22-2018 @ 5:01 AM
  I have had the same problem. I have used valve lapping compound to try and restore a seal but it did not work. I replaced the bottom spring with a heavier one and also used new washers. Still leaks at the stem. It seems that Ford went to a very different petcock in 35-36 but later years use the same petcock (38, 39, 40, 41, Passenger and commercial) Not sure if Southside Obsolete has any of the 40- style. Maybe American Parts in KY?? may have some NOS.


fordmerc    -- 01-22-2018 @ 6:18 AM
  The image posted by 40Coupe is identical to mine, although cleaner. I used polishing compound to try to restore seal with nice cosmetic result on the inside but it obviously didn't solve my problem. I will try again.
If Drbrown has one like it, send me a PM. Otherwise I fear I will have to surrender this bit of authenticity . A continued search to the other sources listed will be done.

This message was edited by fordmerc on 1-22-18 @ 6:23 AM


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