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oil drain plug
#1
Hello,

      Have a 73 Vert with 351 C.  Have owned the car for 5 years and have always noticed that the oil drain plug was a little difficult to reinstall, felt slightly cross threaded. Most recently, it seemed worse and I really had to work with the plug to get it back in.  I torqued to specs and noticed the other day that it is leaking just a little. Seem to remember using a replacement oil plug back in the 70's that was a little larger and sort of cut new threads in the pan and then had a smaller drain plug inside of it. 

       Any suggestions on how to correct this ?  Could I cut new threads in the pan ? Someone suggested getting a brand new drain plug and trying that to see if it corrects the threads in the pan.  Thanks very much !

steve
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#2
The plastic washer should be the sealing point not the threads. The threads pull the plug tight against the plastic washer to seal it.


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David
[+] 1 user Likes Carolina_Mountain_Mustangs's post
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#3
The problem with the oversize self-threading drain plugs is in getting them started straight so the flange is parallel to the pan, so the gasket fits flush against the pan.

Someone likely got yours cross threaded and the last time you installed it it followed the cross threads. It seems like it's always easier to get a nut or bolt started in the cross-threads than the straight ones. If they were crossed, it weakens the straight threads, so it's easy to strip them.

There's a repair kit with guides, a little expensive, but more likely to get the job done right:
https://www.toolsid.com/lisle/lisle-oil-...9535357969

There's also one that require welding a new bung on the outside of the pan:
https://www.macsautoparts.com/ford_mercu...50c22bbe3b

The oversized ones are still available, as well as a rubber screw in plug on a toggle bolt.

The best way, but not easiest, that I've found is to weld or braze a nut on the inside of the pan, after tightening it to the pan with a bolt.



“If you can't explain it simply, you don't understand it well enough.”
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#4
Several years ago, I took my Mustang to a local oil change shop (the last time I took my car to an oil change shop) and the "monkey" underneath stripped the plug threads in the pan. They had their mechanic re-tap it with a metric thread (15mm?) and installed a new plug with a steel and rubber sealing washer. That held up until I had to have the motor rebuilt when a new insert was welded in. I still used the steel and rubber washer as I have found that far superior to the plastic one. No leaks whatsoever.
Geoff.

I learn something new every day!
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#5
(09-25-2019, 07:52 AM)Stanglover Wrote: Several years ago, I took my Mustang to a local oil change shop (the last time I took my car to an oil change shop) and the "monkey" underneath stripped the plug threads in the pan. They had their mechanic re-tap it with a metric thread (15mm?) and installed a new plug with a steel and rubber sealing washer. That held up until I had to have the motor rebuilt when a new insert was welded in. I still used the steel and rubber washer as I have found that far superior to the plastic one. No leaks whatsoever.
Geoff.
Thanks to all for the info.  Appreciate it !
steve
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#6
(09-25-2019, 01:32 PM)naa10104 Wrote:
(09-25-2019, 07:52 AM)Stanglover Wrote: Several years ago, I took my Mustang to a local oil change shop (the last time I took my car to an oil change shop) and the "monkey" underneath stripped the plug threads in the pan. They had their mechanic re-tap it with a metric thread (15mm?) and installed a new plug with a steel and rubber sealing washer. That held up until I had to have the motor rebuilt when a new insert was welded in. I still used the steel and rubber washer as I have found that far superior to the plastic one. No leaks whatsoever.
Geoff.
Thanks to all for the info.  Appreciate it !
steve
 I tried to find a pic of the sealing washer I have, but none I found were exactly the same and I don't have a spare. However if you can picture it in your mind, it is sort of a castellated steel washer with a rubber center molded in. Hope that makes sense. If you can't find anything like that there are other steel/rubber ones listed for oil plug washers.

I learn something new every day!
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#7
You can also use a copper washer, and most auto parts stores have these in various sizes. That's what I used in all of my classic vehicles. They are also re-usable for a number of oil changes.

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http://midlifeharness.com

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#8
(09-25-2019, 06:10 PM)midlife Wrote: You can also use a copper washer, and most auto parts stores have these in various sizes.  That's what I used in all of my classic vehicles.  They are also re-usable for a number of oil changes.
 True, but I feel that if the thread is already stressed, the pressure to seal a copper or even plastic washer might be too great and eventually do more damage. The rubber one I describe also is reusable for a couple of changes at least. 
Just my thought on it.
Geoff.

I learn something new every day!
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