I couldn't get the drain plug out.

Image Unavailable, Please Login Image Unavailable, Please Login So I got my car up on a lift today to do some fluid changes. Oil and antifreeze went off with out a problem. I then tried to remove the drain plug on the rear differential. I haven't changed the differential oil since I've owned the car. I have checked the fluid level using the fill plug. I used a 1 5/8 socket which was a nice tight fit. I used a 3/4" ratchet on the socket. Even with the big ratchet I couldn't get the plug to budge. I elected to not use any additional force because I didn't want to break anything. I figure I can either take the rear cover off or use a small electric pump to suck the old oil out.

Anyone have any idea on why I couldn't get the plug out?

 

Was the plug ever changed out? Might have been replaced with one of a different material. Dis-similar metals can gall, particularly on threads.

 

I use the correct sized socket , which is a 41 or 46mm, can't remember which. Then my 1/2" drive air impact has no problem loosening the drain plug.

 

Image Unavailable, Please Login Image Unavailable, Please Login If you can chisel out the washer, the pressure will be relieved and the plug will come out. On my 246 Dino we had the same issue. We also had to use a chisel to turn the plug by chiseling a groove in the plug. It looked ugly but it came out.

Using a impact wrench stripped the plug in my case.

 

Applying heat often helps. e.g. from a hot air gun. Percussion with a hammer sometimes helps to loosen things up. This is why impact tools work so well.

And if you had unlimited funds, you could buy one of those Mini-ductor Venom tools

http://www.theinductor.com/induction-heating-products/mini-ductor/models/md-venom

 

True an impact force is more apt than brute force, to break a fastener free. When an impact guns is a bad choice (galling threads), the hand held impact drivers that you rap with a hammer work well. Particularly in dissimilar metal situations. For those, I also apply wintergreen oil, which is a terrific penetrant and corrosion breaker.

Thanks for that tip @Qavion. Looks just the ticket for releasing thread-locker.

 

It is just tight. I have never seen a dissimilar metal issue with stuff immersed in oil.

 

But sometimes the oil dries out. A better insurance policy is silicone tape on the threads when installed to minimize the galling.

 

Never x2 on an oil drain plug! Add oil drain plug is not a water system pipe fitting that uses teflon tape.

 

Looks like a brass plug with aluminum alloy housing and maybe copper washer. If you used a 3/4" drive on it already and no budge then proceed carefully. If your socket was not a steel impact socket then buy one. They are very thick and fit tightly. Use some heat on the aluminum with a MAPP gas torch and maybe some freeze spray on the plug to break the tension. Apply some PB blaster as well and let sit. Hit it with an impact at low reverse setting. Hold the gun straight and firmly. If no movement then stop and dig out the washer as suggested and repeat the process. Go slow. If you feel spooked then have a mechanic with lots of experience take a look.

 

Socket wrench breaker bar and maybe even a galvanized pipe on the end of the breaker bar it will come out. Start the car get the engine to operating temperature it will help as well. I once had a Mercedes diesel and you could not get the glow plugs out when the engine was cold but when the engine was at normal operating temperature they came out just like a spark plug.

 

Good point! The old thermal expansion of metals thing!

Probably safer as the first attempt rather than the breaker bar thing in case the extra torque causes the threads to get damaged which in turn may cause the extra step (and hassle) of repair tapping and possibly getting a new sized plug that won't leak. I hate corrosion!

 

Like Streetsurfer said, use a good-quality hand-held impact with a dead-blow hammer.

In any case, when you put it back together, use anti-seize compound and of course a torque wrench. Go a little less than the torque specs, because the anti-seize reduces friction in the threads and thus increases axial force.

 

Thanks everyone for the info. I just put the car away for the winter so I have 6 months to get it done.

 

There is no need to use any sort of tape nor sealant on an oil drain plug with a crush washer that has been properly torqued.

 

Could you share what the subject car is with those of us who can't guess from a drain plug photo?

 

Yes, 1975 365 GT4 2+2.

 

Ha, I was at the North Pole on Monday...went to the Pagoda...bleh.

 

No to this!!!

 

This usually occurs when the crush washer is reused. This is also the main cause of damaged threads. Proper torque specs and sealing of these is based on a new copper crush washer. Generally a used washer will leak and they are then tightened further to seal the leak. It is the main reason I stock a large selection of Heli-coil kits for these old pans as a great deal of them need repairing when they arrive.

 

Windsock is right on the money: the crush washer work-hardens when reused, meaning it can't deform enough to seal.

An old temporary fix if you did not have a Heli-coil handy was to use a spark-plug washer as that had a crush zone. Good luck finding one today, as they are mostly tapered threads,

 

You heat up the old washer, let it anneal, and then re-use it. Only if there is no new one anywhere close to a mile radius of course.

 

Just visiting? Perhaps looking for some northern lights?

 

On business Jim, but had a fun time. Got a selfie with old St Nick...

 

Brian gave the correct answer in post 3. I always do it that way. Reinstall with new washer and a 1/2 inch ratchet.

Lets not get analysis paralysis over this. Plugs tightened on a copper washer always take far more torque to remove than to install.