B&S drain plug just screws in, never tightens

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Hi all,

Long time lurker here. Apologies if this has been covered before. If so, please post a link to the thread.

I've got a drain plug on a 6 HP B&S engine that just won't tighten. It has no resistance at all. I screw it in with my fingers and it never stops. I could easily screw it in all the way until it plunks into the oil pan. The plug has no shoulder on it, just a recessed 3/8" drive opening.

I don't recall this being a problem on previous oil changes on this engine, though it's been a few years since the last one.

Should I replace the plug, or can I use something like Loctite Blue 242? And how far should it be screwed in? I'm guessing at flush with the bottom of the block.

Engine model #: 12Q802-0202-B1. Date code: 02120259. I've owned it since new.

Suggestions graciously accepted
 
Find a standard hex head bolt with the same threads. See if that is loose as well. If not, just use the bolt. If it's too long, screw a nut all the way down on it, cut off the excess, then screw the nut off. The nut will clean up the threads on the way off.

You can get the plug some grip by GENTLY peening the threads with a small hammer. That'll help it stay put but it won't do anything for leaking. You'll still need some sealant and/or lok-tite.
 
What is the plug made of? I might be tempted to buy another one if its steel. Weld a slightly larger washer to the back of the plug.
 
Originally Posted By: HangFire
Find a standard hex head bolt with the same threads. See if that is loose as well. If not, just use the bolt. If it's too long, screw a nut all the way down on it, cut off the excess, then screw the nut off. The nut will clean up the threads on the way off.

Good suggestion. I've shortened bolts this way before. Thanks for the reminder.
 
Originally Posted By: spasm3
What is the plug made of? I might be tempted to buy another one if its steel. Weld a slightly larger washer to the back of the plug.

I've no idea, but I suspect that the plug is some sort of steel. Trying a new plug is probably cheaper and faster than learning how to weld...
 
If it's a tapered plug (or was) and has been screwed in past the wrench end then there is no taper left.
 
Quote:
If it's a tapered plug (or was) and has been screwed in past the wrench end then there is no taper left.

Huh. Yeah, that makes sense. If the loss of taper is just on the plug and not also on the threads in the case, then it should be an easy fix.
 
The plug or the block is stripped, after repair tip the lawn mower on its side to drain the oil out of the fill hole.
 
The plug or the block is stripped, after repair tip the lawn mower on its side to drain the oil out of the fill hole.
 
Originally Posted By: SHOZ
If it's a tapered plug (or was) and has been screwed in past the wrench end then there is no taper left.


Most likely.

A reducer bushing can be epoxied into the VERY clean and well-degreased threads, then you'd have the next size smaller thread plug.
 
That plug is a tapered "pipe thread". the threads are slightly smaller on the end and taper slightly larger towards the end with the square drive.
The block is tapped the same way to work with this plug.


Unfortunately, you have a steel pipe plug going into an aluminum block, so if it has been over tightened, it more than likely ruined the threads in the aluminum block.
You could try a new drain plug, but I doubt the steel plug was damaged before the aluminum threads in the block.
You don't have to go nuts tightening these, just snug it with a 3/8 ratchet.

If you can find a reducing fitting at a hardware or plumbing supply store that might work, then you can just use a smaller drain plug inside the bushing.
 
Originally Posted By: cronk
That plug is a tapered "pipe thread". the threads are slightly smaller on the end and taper slightly larger towards the end with the square drive.
The block is tapped the same way to work with this plug.


Unfortunately, you have a steel pipe plug going into an aluminum block, so if it has been over tightened, it more than likely ruined the threads in the aluminum block.
You could try a new drain plug, but I doubt the steel plug was damaged before the aluminum threads in the block.
You don't have to go nuts tightening these, just snug it with a 3/8 ratchet.

If you can find a reducing fitting at a hardware or plumbing supply store that might work, then you can just use a smaller drain plug inside the bushing.

I think that this is the problem. I can see and feel the taper in the plug now that I'm looking for it. Never noticed it before.

There's a small engine shop not far from here that I'll go to tomorrow, to get their take on it. I recall that there were brass inserts to fix stripped spark plug holes back in my air-cooled VW days, so maybe a reducing bushing will be the right way to go.

Thanks, everyone. I'll keep you posted.
 
UPDATE: No go on finding a reducer. I got a 3/8" pipe plug, and while it did snug up, it did not seal. I then went back to using the original drain plug. I cleaned all threads and applied Loctite Blue 242. It seems to be working. I mowed for an hour yesterday and the plug is bone dry today.

Subsequent oil changes will be through the dipstick/fill tube, so I doubt that I'll be touching this plug in the future.

Thanks again for the speedy explanations and suggestions.
 
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