Plastic Radiator Petcock Fix - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 5 (permalink) Old 01-28-2010, 03:37 PM Thread Starter
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Plastic Radiator Petcock Fix

Anyone with a late model Ford car or truck from the early 80's till probably now has no doubt experienced this problem with the plastic radiator tanks.

The petcock valve screws into the tank and seals on a rubber gasket. The first or second time that you unscrew the valve to either replace the coolant or service the engine, the valve will not seal properly again. The problem is that the threads on both the valve and the radiator tank strip easily and you now have a leak. You could buy a new radiator, but I have found an easier, cheaper and reliable way to permanently fix this problem.

Here is the valve in it's native state:

Once the valve is un-screwed, the threads are usually stripped and the valve will no longer seal:

Here you can see the hole that the water drains through at the top of the photo:

I use an expanding rubber plug to seal the main hole in the radiator. A plug that will fit a 1"-1 1/8" hole works perfect. When you turn the nut on the plug, the rubber expands and seals the hole:

The plug is placed in the radiator and tightened until snug:

A short piece of 3/8" hose, a 3/8" bolt and a couple of clamps will seal the drain hole:

The hose is placed on the nipple, and everything is tightened down. The next time you need to drain the coolant, you can remove the rubber hose to drain:

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Last edited by F15Falcon; 01-31-2010 at 07:16 PM.
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post #2 of 5 (permalink) Old 02-01-2010, 05:11 PM
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Re: Plastic Radiator Petcock Fix

now that is a money saver there! Sweet!

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post #3 of 5 (permalink) Old 02-02-2010, 02:08 PM
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Re: Plastic Radiator Petcock Fix

Sweet idea.
I did that for a oil pan plug once.
Holds to this day.

Rich Sr.

Last edited by ixtlan; 02-02-2010 at 02:19 PM.
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post #4 of 5 (permalink) Old 08-10-2014, 02:52 PM
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Question Re: Plastic Radiator Petcock Fix

i have my 89 taurus gl wagon sitting at home depot and the petcock and the insert it threads into blew out on the highway so i found this thread (after 3 days of research lol) and i have done this fix but i cannot figure out how to keep the plug in the hole while tightening it keeps pushing itself out when i snug it need tip or something thanks
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post #5 of 5 (permalink) Old 08-11-2014, 12:26 AM
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Re: Plastic Radiator Petcock Fix

The plug is rubber molded around what is equivalent to a washer with a stud on it. When you tighten the nut, it pulls the washer towards the nut, expanding the rubber between them. Check your plug for excess rubber on the end. Remove any of it you can so the plug will seat deeper and try again. Perhaps Tommy (the original poster) had a different and shorter plug brand.

If all else fails, I have seen two other methods used. One is to set a freeze plug in with RTV or epoxy, although that's permanent, and future draining would be by removing the lower radiator hose. The other is a slightly over-sized bolt or screw that will re-thread into the old thread hole, with an O-ring or faucet washer under the bolt head. Use whatever works for you. Good luck, and let us know what you come up with.


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