Cobra Oil Pan Stripped Drain Plug Hole

[SHELB66]

Turns out the drain plug hole on my '66 Hertz aluminum oil pan is stripped.  Looks as if this isn't a new issue as the plug that was in there is a self-threading one (see pic).  It always dripped a bit and I thought replacing the old nylon washer would help.  The situation is worse as there are just not enough threads remaining.  I have a temporary plug in there now which works just fine.  What's the preferred permanent fix short of removing the pan.  I'm leaning towards a self-tapping piggyback unit.  Thoughts?

Craig R.

[Bob Gaines]

My thoughts are to not waste your time with a temporary fix. This time of year is typically the best time  to take your car out of service to do a fix. These chores always seem to come at a less then ideal time.

[SHELB66]

Thanks, Bob!  The temporary fix is so that I can drive it down to the shop that I deal with.  It's due for an alignment and I will get the pan fixed at the same time.  This will probably be after Thanksgiving.  I was just looking for feedback on repair methods.

Craig R.

[6R07mi]

" The temporary fix is so that I can drive it down to the shop that I deal with.  ..... and I will get the pan fixed at the same time."

just wondering what the intended "fix" is?  Helicoil or TIG weld up the hole and re-tap??

jim p

[trotrof1]

Weld up the aperture, drill, retap. Professionally completed you cant see any repair.

[Bob Gaines]

Weld up the aperture, drill, retap. Professionally completed you cant see any repair.

+1

[SHELB66]

The temporary fix is in place.  The permanent fix that I am considering is a piggyback unit shown in the photo.  The outer bolt is used to rethread the pan while the inner bolt is the new drain plug.  The use of a helicoil is also a possibility.  Obviously welding the opening closed then drilling and tapping is ideal but I'm trying to avoid pan removal.

Craig R.

[Bob Gaines]

The temporary fix is in place.  The permanent fix that I am considering is a piggyback unit shown in the photo.  The outer bolt is used to rethread the pan while the inner bolt is the new drain plug.  The use of a helicoil is also a possibility.  Obviously welding the opening closed then drilling and tapping is ideal but I'm trying to avoid pan removal.

Craig R.

Helicoil would also require pan removal to safely insure that metal shavings from the installation process from contaminating the inside of the oil pan .
Fixing it right is more trouble but your band aid piggyback fix will be very visible to anyone looking under the car. Based on your past posts about assemblyline type details I get the impression that you will not be satisfied with that band aid fix as permanent .Best of luck what ever you decide.

[deathsled]

If it were me I would send the whole pan over to Shelby Parts and Restoration and have it professionally restored. They probably would line the pan with something as well, as it is my understanding that the aluminum in these pans is very porous.

[shelbydoug]

I don't remember the size of the original plug but I would think that there is an oversize plug that will work without taking the pan off.

You are going to have very little metal filings involved and they can be flushed out by running oil through the pan.


As far as the pans leaking due to porosity? I don't think anyone would be able to tell the difference of where they leak from to begin with but it is more common then not that they will leak through the mounting flange and the bolt holes.

As far as lining the pan internally, I'd want to see the procedure and what the lining material is. Cast aluminum is not a friendly medium to apply witch doctor solutions to. You can't even weld on it dependably.

I think that is something to stay away from.

[s2ms]

Did mine almost 10 years ago without removing the pan using a Keensert, sort of a helicoil on steriods. You can significantly minimize metal filings by coating the drill bit and tap with grease which will trap most of them. Only drill and tap slowly over short distances then backout, clean the grease with filings off, repeat until done. Then I did exactly as Doug suggests and ran a few quarts of thin oil, 0W-20 I think, through the pan before installing the Keensert. IIRC, also did an oil change shortly after.

[SHELB66]

        "I don't remember the size of the original plug but I would think that there is an oversize plug that will work without taking the pan off."

This is basically what the piggyback unit is.  They come in various sizes.  You won't be removing the bolt that makes the new threads each time you do an oil change.  That's a good thing as the drain plug hole is already compromised having been threaded three times (original, 2nd time by a previous owner, and now).  To drain the oil one just remove the drain plug that is within the bolt that is threaded into the pan.

Craig R.

[kram350]

Once you get it repaired just a suggestion,  use a stat-o-seal gasket on the plug. Also wrap the plug a few times with teflon tape.

[rhjanes]

This is for daily drivers and other non-original cars.  I've been using Fumoto valves for years. 
https://www.fumotousa.com

Their latest are an improved design where you can rotate the valve prior to the final tightening on initial installation.  After that, a clip, flip the valve open and the oil drains.  It does drain slower than the plug because the Fumoto valve restricts the flow.  No more removing the plug.  I rotate tires when I change the oil on the daily drivers so I loosen all wheel nuts, jack up the front corner, start draining, jack stand that front end and go about rotating all four tires.  When I'm half done, the oil has drained, flip the valve shut, wipe up, reposition the drain pan and remove the oil filter.  Continue the last two tires and then install the new filter, one last check before lowering the car and filling with oil.  I can do it all in an hour (except maybe the F250) and have not removed a drain plug in years on the drivers.  The two classic Mustangs still have drain plugs but the 2008 GT convertible has a valve on it.

If you go Fumoto, get the locking clip with it. 

[deathsled]

I don't remember the size of the original plug but I would think that there is an oversize plug that will work without taking the pan off.

You are going to have very little metal filings involved and they can be flushed out by running oil through the pan.


As far as the pans leaking due to porosity? I don't think anyone would be able to tell the difference of where they leak from to begin with but it is more common then not that they will leak through the mounting flange and the bolt holes.

As far as lining the pan internally, I'd want to see the procedure and what the lining material is. Cast aluminum is not a friendly medium to apply witch doctor solutions to. You can't even weld on it dependably.

I think that is something to stay away from.

Here is where I first learned about coating an aluminum pan.
https://www.saacforum.com/index.php?topic=13417.msg111356#msg111356