Radiator petcock leaks

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5 WoodenWheels
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Radiator petcock leaks

Post by 5 WoodenWheels » Tue May 17, 2022 4:08 am

Pretty good leak, I lose about a half gallon over the course of a week with car parked. Drip drip drip. Is the petcock replaceable? Rest of the radiator is in good shape. ‘23 Touring and hot weather around the corner. Thanks for any help. Gerrit


Allan
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Re: Radiator petcock leaks

Post by Allan » Tue May 17, 2022 4:27 am

It's the same petcock used on the pan. Perhaps replace it with an oily one from an old pan. It just screws in on a tapered thread. A bit of sealant around the thread may help.

Hope this helps.
Allan from down under.


Professor Fate
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Re: Radiator petcock leaks

Post by Professor Fate » Tue May 17, 2022 4:30 am

https://www.modeltford.com/item/3079RE.aspx

Back the old one out slowly using pliers or an adjustable wrench. Go easy.... Don't want to break anything. Wrap some white Teflon tape on the threads of the new one before u install it.
Sometimes rust will collect at the petcock enough to stop the leak as driving season goes forward. Use a 3 inch piece of coathanger to jab thru the open petcock to get it to drain when you need to drain coolant or distiled water... I've had a leaker for years that usually quits once rust clogs up the petcock.... part of the cars personality at this point. I keep intending on changing it but never seem to get around to it.
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Topic author
5 WoodenWheels
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Re: Radiator petcock leaks

Post by 5 WoodenWheels » Tue May 17, 2022 5:13 am

Thanks for the replies. I should have clarified that it’s leaking from the petcock itself, where you’d normally drain the coolant. I’ve tried fiddling with the screw to see if there’s a “sweet spot” that would stop the drip but to no avail. From the info you’ve provided it sounds like I can try a new one or at least a good old one. Thanks again. Gerrit in Maryland.


John kuehn
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Re: Radiator petcock leaks

Post by John kuehn » Tue May 17, 2022 9:08 am

The same petcock is used for the radiator drain, oil pan, and the sediment bowl drain.
I realized that years ago and when going to swap meets started to pick them up going through old car junk boxes people gather up and put on trailers to sell. I found lots of them that way and I’ll bet others have to.


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Re: Radiator petcock leaks

Post by Russ_Furstnow » Tue May 17, 2022 9:24 am

I have used toothpaste to "lap" the petcock body and the tapered shaft with success. You need to remove the cotter key, spring and small washer from the tapered shaft and then clean the petcock parts thoroughly. Place a small amount of toothpaste on the tapered shaft and insert it into the petcock body and turn the shaft back and forth. When finished lapping the parts, clean the toothpaste from the parts. Before reassembly, stretch the spring slightly. Assemble the petcock and check out the results. I've had good luck with this process. I hope this helps, Russ Furstnow


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Re: Radiator petcock leaks

Post by jiminbartow » Tue May 17, 2022 2:17 pm

The petcock spring applies tension the keep the tapered shaft pulled tight against the housing. Over time the tension of the spring can loosen. You might stop the leak if you dismantle the petcock and pull the spring apart a little so there is more tension on the spring to seat the shaft more tightly in the housing. A little grease on the shaft before reassembly may help to create a better seal. Jim Patrick


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Re: Radiator petcock leaks

Post by Guardian1fox2 » Tue May 17, 2022 7:00 pm

This might sound dumb, but my petcock leaks like a sieve as well. I took a rubber nipple, that you would put over a vacuum port on a carburetor; and it fit perfectly on the end of it and solved the leaking lol. You can get a pack of various sizes from local store for like $3. Band aid of course.


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Re: Radiator petcock leaks

Post by Allan » Tue May 17, 2022 7:09 pm

Gerrit, you mention fiddling with a "screw". Do you mean trying to screw the tap handle? If there is a screw, the petcock may be an early one. In about 1913 the tapered shut-off was changed to have a spring, washer and split pin to hold it in place, the spring being fitted to keep tension on the unit and the taper fully engaged. When the early taps wore on the taper, there was nothing to keep the taper firmly engaged, so they do leak with wear, and can even vibrate open. I had this happen on my 1912 Van on a pan tap. Fortunately, it opened up over a bump just before a planned stop, and the oil trail alerted me to the problem before any damage was done.

Allan from down under.


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Re: Radiator petcock leaks

Post by jiminbartow » Tue May 17, 2022 7:26 pm

As Russ recommends, it would be a good idea to lap the tapered male shaft to the tapered female interior housing just like valves are lapped to the tapered exhaust and intake ports using a lapping compound to rid the surfaces of scratches that might allow leakages. It should not require much to restore new surfaces to brass parts. Jim Patrick


Topic author
5 WoodenWheels
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Re: Radiator petcock leaks

Post by 5 WoodenWheels » Tue May 17, 2022 10:46 pm

Thanks for the suggestions. The “screw” I referred to is the thumbscrew you turn to open or shut off the flow. I’m fairly new to antique cars but it looks like a standard part common to the model T. The car is keeping me on my toes with water leaks—first I eliminated the add-on water pump from the previous owner because it REALLY leaked, and now I’m down to one leak from the petcock. Guess I’m out of warranty with all this but at least it gives me a chance to know my car. Thanks for all the help, I’ll keep you posted. Gerrit

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