1948 Cadillac oil pan drain plug

[Bruce Watson]

After having this car for over a year and a half I have only put 500 miles on it so I thought it would be a good idea to change the oil.

The oil pan drain plug was slightly pushed in and the plug was somewhat rounded off. This made it impossible to get a regular socket wrench or even a box end wrench on it. I took it to a local garage thinking they may have a solution. That didn't work. There answer was i should buy a new pan.  I am sure if I was able to get the old plug out a new one would work ok.  If anybody has any idea's of the best way of getting this plug out I would appreciate some input.

Thank you

Bruce

[Otto Skorzeny]

If you can't get a purchase on the rounded off nut, I would remove the pan and tackle it from both sides. You can apply penetrant to both ends of the threads and you'll be lees likely to distort the pan if it's frozen in place.

You can also try spot welding a new nut of any size to the head of the old one if it's steel and not brass.

[Mike Josephic CLC #3877]

I would try heating the drain plug up with a heat gun or even a popane torch
(don't overdo the torch -- if you have gasoline leaks don't use this method!).

Then, use a large size vise grip.  If that doesn't get it to budge then dynamite
may be your only option.  Just kidding -- then pan removal is called for.

I hope the plug is not cross-threaded or stripped.  This is a common problem,
caused by a grease monkey not paying attention to what he's doing.

Mike

[Jim Stamper]

     With access,and a hand grinder I have ground new flats on a rounded off plug, assuming it is big enough. Sometimes just grinding down two sides enough to get a big Cresent type wrench will do it or re-hex it to the next smaller size and put a six point wrench or socket. I use six point sockets or wrenches when ever I can. Better contact and a lot less likelyhood of rounding off the nut or plug flats.

[Steve Passmore]

Bruce, Be very careful of applying heat of any kind to this drain plug, a lot of them were brazed in place and you could melt out the entire boss that its threaded into,   yes, Ive been there, done that
I would remove the pan, tap it back into shape and perhaps you could get a better tool around it. Last resort, drill it out and re thread it.

[bill henry]

I place a big nut over the rounded on and weld together with my MIG and then removal is easy.

[Mike Josephic CLC #3877]

Question -- if applying heat will losen the boss on the pan due to it being brazed in
place --- how do you get around this when (as several have recommended) you weld
another nut onto the drain plug?

Just curious.

Mike

[Mike Simmons 938]

So, a pipe wrench and some elbow grease is not feasable? It's junk now. remove it and get something else that fits correctly.

[Steve Passmore]

Posts: 768





Quote

Question -- if applying heat will losen the boss on the pan due to it being brazed in
place --- how do you get around this when (as several have recommended) you weld
another nut onto the drain plug?
Quote

I second that Mike, Ive done it, That boss wall is very very thin.

[bill henry]

4 quick tacks with a 110 mig wont get it that hot.

[Steve Passmore]

I don't think four quick tacks will hold a big nut of that size when the bolt its tacked to is already stuck, but what do I know?

[bill henry]

Well I have been a machinist for 24 years and this is the prefered method in our shop which serves everything from small hydraulic valves to immense industrial equipment. The key is make a tack let it cool do another let it cool until you fell you have enough. In time you will have a solid weld.

[Steve Passmore]

I didn't know this was a contest I can add a further 23 working years to your total restoring antique cars but thats all academic. I have seen this happen a few times with flathead oil pan drains plugs and have had it happen three times on my own engines, as soon as these engines are placed on the ground or hit something on the road the drain plug gets punched in.  Your idea could work, and I would like to think so for Bruce's sake, but these plug heads are very shallow, when rounded theres hardly anything left of the bolt and the head is the same size as the boss its screwed into, so being right next to it, you can end up welding the bolt to the boss, compounded by being pushed in theres a problem as to whether you could even get to it with the MIG, not to mention that its under the car and the braze is right next to it. If its as damaged as Bruce has said and one automotive garage has refused him I think the pan still needs to come off to weigh up the options and for ease of working on it if nothing else.

[bill henry]

I was not making it a contest in the above post you said " but what do I know" and I was explaining why I believed that this would work. But needless to say I have learned something here.

[Steve Passmore]

Hey bill, I'm intrigued, How do you post a moving picture on your profile?

[bill henry]

I hosted the GIF on photobucket and then linked it to my avatar.

[Bruce Watson]

I can't thank everyone enough for all their idea's & help. I considered the heating of the plug but was concerned  with the possbility of a fire. I have tried the pipe wrench without any luck. After realizing that the plug was never going to be used again I started using a chisel & hammer on the plug & after a short period of time I was able to break it loose. I was able to find a new plug that protruded a little further than the original & it worked like a damm. This saved taking the pan off & with the new plug, which I  tried putting it on & off a few times, everything is back to normal.

Bruce

[Otto Skorzeny]

Always good to hear about a simple cheap fix.