is the automatic transmission pan drain plug is a 5mm allen or a torx bit? I don't want to use the wrong tool and mess things up.
I understand it takes a good amount of force to break it loose, is this the normal case? Has anyone used a heat gun with good results?
All help is appreciated.

 

It's a Torx. We just did a trans fluid change. Could not get that drain plug out, even with heat. Tried an impact wrench and that didn't work either. Eventually stripped the inside. Ended up removing the pan to drain everything out. Messy, but we got it done.

 

I haven't started yet but expect the same out come ... not looking forward to the mess

 

Just use a breaker bar so you have more leverage. I was able to loosen the bolt and drain the trans pan before removing it. Sometimes I tighten the bolt and then loosen it. You can also spray some penetrating spray on it and let it do its job.

 

did you use allen or torx bit?

 

I think I found the answer ... quoted from MB World "On the 722.6 trans, the drain plug has always been an allen. Size of the allen is either 5 or 6 mm."
Thanks all for your input ... seems reasonable using a torx bit is why so many have rounded the inside and not been able to remove the plug

 

The Allen key does not go in easily and is deep. Make sure the Allen key is fully inserted, or you will strip it even with proper Allen key. It will require a breaker bar to loosen.

 

Thank you for the information ... the more information I have the better ... your help is appreciated

 

Update ... Transmission drain plug is 5mm Allen ... was able to fully seat the allen in the plug and using a 16" breaker bar, that drain plug was not about to give up and break loose ... using heat from a heat gun made no difference ... was not able to get the drain plug out ... next step was to drop the pan and watch the fluid run all over my garage floor ... 5 of the pan bolts easily broke loose, the 6th pan bolt must have been in cahoots with the drain plug ... it was seized and would not move no matter what I did ... retorqued the bolts that did break loose, put away my tools and poured a cup of coffee

I talked with an independent Mercedes shop about 35 mile away ... they assure me they have seen this before and can take care of my problem ... so I will make an appointment and put it into their hands ... all of this just because I was trying to replace a transmission filter at 100k mile service ... I still love these cars

 

I give you credit for trying your best. You made a good decision though. I wouldn't want to snap one of those bolts. Then it becomes a real nightmare!
Best of luck to you!