Suggestions for repairing drain plug - PeachParts Mercedes-Benz Forum

Bajaman · #1 01-15-2008, 12:18 PM

I guess this isn't really diesel related, but this is the only area I ever visit. Anyway I'm getting ready to install a 4spd manual in my TD as the slushbox decided to go south. As I was looking things over, I noticed that some idiot used a chisel to remove the drain plug rather than getting a 14 mm hex drive. In the process, they mangled the plug so bad, that I couldn't get the hex drive in without cleaning up the damage done. Once I finally got the plug out, I found that It has been seriously cross-threaded, and the threads are completely unusable. So, down to the real question. What are some suggestions of how to repair this. Currently, I'm thinking about tapping it to a 1" or 3/4" pipe, but there isn't a lot of material there. If I got real desperate, I could try to tig in a new bung... Let's hear some ideas
bb

jshadows · #2 01-15-2008, 02:25 PM

are you talking about the lower oil pan then? I assume it's not the tranny since you're removing that.

If lower oil pan, just find someone who's tearing down an engine for good and get the oil pan. I'd have one for you, but it's in New Orleans and I'm about 4000 miles away from there right now.

Bajaman · #3 01-15-2008, 02:29 PM

No, it is the tranny. I'm talking about the four speed that I'm putting in. The main housing is one piece and its aluminum, thus the stripped, messed up threads.
bb

xtreme barton · #4 01-15-2008, 02:59 PM

cant you just tap in new larger threads ?

jshadows · #5 01-15-2008, 03:02 PM

Quote:

Originally Posted by xtreme barton

cant you just tap in new larger threads ?

that would be my thought too. Might be worth taking it to a reputable machine shop to have a look..especially if you have limited material to give it bite.

rs899 · #6 01-15-2008, 03:09 PM

Retapping would be best, but since there's no pressure in there, that leaves room for some creativity. You may be able to find one of those rubber plugs that are used to repair freeze plugs on engine blocks. or perhaps one of those rubber plugs the boyz at Jiffy Lube use when they punch a hole in your slushbox pan to change the ATF....

As long as you check whatever you use periodically and it is secure enough to NOT catastrophically fail ( but just leak a bit)....

How about something as simple as a toggle bolt with a rubber disc backed up by a plate keeping it tight?

Rick

Bajaman · #7 01-15-2008, 04:41 PM

The rubber plug is a thought, but I hesitate to put something flimsy in... I'll have to compare it to standard pipe sizes tonight. I know I have access to a 1" pipe tap, not sure about 3/4.

Bajaman · #8 01-15-2008, 04:44 PM

Fine threads are definitely better, but availability really bites. I would have to special order a tap and bolt. Does sound better than pipe threads though.

Diesel911 · #9 01-15-2008, 04:41 PM

Rather than using a pipe tap you could use a regular National Fine tap of the closest over size and use a bolt with a copper waser and for good measure a little silicone sealent. The benifit of this is that 3/4 and 1 inch pipe taps have big threads the cut deep into that thin metal and because they are tapered will enlarge the hole even more and then when tightened put alot of outward pressure on the metal around the hole. The National Fine threads and the fact that the hole would not be cut tappered when tapping would preserve a lot more of the origional metal. Also for alot of aluminum parts regular rubbing alcohol works well as a tapping fluid.
Another way: Clean and degrease the cross threaded area. Get a new hex plug; clean and degrease the threads to to thee bare metal. Use JB weld or another epoxey that is rated for temperatures above 200 degrees and screw the plug in tight; let it harden (I believe it must be 60 degrees or above to cure correctly.) After it is hardened drill and tap out the hex plug for a smaller american NPT pipe plug.