Those leaky lower-hose drain petcocks!

B

Bobs29ModelA

Senior Member
I recently made the mistake of replacing an old lower hose drain petcock on my car, only to find that the new replacement was leaking (as in a slow drip) a couple of days later. I gave it a while to see if maybe it would stop on its own, but it didn't. I then replaced it with yet another new one, only to have the exact same thing happen again. In both cases, I'd purchased the more expensive "US-made" unit, instead of the cheaper Chinese-made unit. Needless to say, I'm very disappointed with all this, especially with the prospect of losing coolant a second time, while trying to put-in a 3rd new valve... with still no guarantee that it would be any better than the first two replacements.

Anybody have the same experience, and/or, come up with a more reliable replacement for these things? I'm now considering just putting a tapered brass plug in there and calling it quits!
 
I wonder if it could be lapped in like a fuel valve.
For lapping, I use rottenstone powder mixed to a paste with paraffin oil. It is VERY fine grit. Works super for polishing nickel plating also. Pumice stone powder is the next coarser grit. Available at most paint or hardware stores.---Bill W.
 
Following recommendations here on the barn, I gave the original brass valve a 40 - 50 turns with fine valve lapping compound. No leaks in the two months since then.
 
Don't you also need to make sure the thing that turns is "seated" in the body of the valve? In otherwords the spring on it may not hold the turn **** tight enough to get a good seal. May help to lightly tap the **** in on the latch end of this ****. (My terms or out in left field but you may get the idea of what I am trying to say)
 
seems like it may be leaking from the pipe if you are using an original pipe and a new petcock. i bought a new pipe and petcock from brattons never had any problem
 
Had a similar experience -- appeared to be a new leaking petcock -- installed another "new" petcock -- still leaked -- thoroughly investigated with flashlight & found pinhole leaking in joint between metal tube & female threads of petcock -- soldered pinhole -- no more leaks -- could have installed 100 "new" petcocks & "all" would have appeared to leak -- with moving light reflection, flashlights help to "see" sources of all types of water leaks.
 
Go to a hardware store and buy a small brass valve to fit the thread but ask for a "ball" valve style they do not leak last for years, Have a great day Gord, B by the bay
 
I must be lucky..I have restored original petcocks,, about a dozen or so over the years with no leaks. I was told long time ago lapping with tooth paste so that's what i use on all ..even gas filter bowls... Now i am knocking on wood!!!!:rolleyes:
 
I think if I remember correctly there's a nut and spring on the back of the valve...i believe if you try tightining the nut a little it may stop the leak. It would be worth a try if you don't want to take it off again. If it dosen't work you can always take it off and lap it in. If I'm wrong about the nut and spring, I appoligize. Haven't looked at mine in a while.
 
FYI, it is a brand-new lower pipe, with new petcocks being installed on it. A very close inspection shows it to be leaking only from inside the actual drain hole in the valve, and not from the threaded area or from the pipe. I, too, had also put teflon tape on these pieces prior to installing them, and the threaded portion seems to be nice and dry.

I may do one of many things... first, I could try removing it and "lapping" it, as suggested... or, I could remove it and put a simple threaded brass plug in there... or, I could remove it, and install a brass adapter that provides a larger threaded opening, and then install a "modern" (as in from the muscle-car era) shut-off valve, which I happen to have in-stock, and have also never had any leakage problems from. Doing the latter might also help to resolve another problem I've noticed... that when you do drain these things, they're so high up that it gets coolant all over the steering linkage, among other parts. Perhaps adding an adapter, which would lower where the drain actually pours out, might make it easier to use than if I stick with the original design?
 
Same issue here, in fact Sunday I plan to pull the pipe and replace it with a stainless one with a new (and hopefully leak free) valve. Its time to change my antifreeze anyway but when I put the drip tray under the car I figured it would catch oil, not the antifreeze that drips down the engine pan. The valve worked fine when I first got it, until I used it once, then I could never get it to seal again.
 
Unfortunately, I'd tossed the original one, because it was kinda crusty when I first got the car... although, to be fair, it didn't leak, from what I could see!

I thought I was being a smart car-owner by replacing the lower pipe with a new stainless-steel one, along with a new valve. Silly me.
 
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