Block drain plug repair

[Stevenph]

This week when i went to reinstall my aft drain plug (after a winter of various projects and cleaning/re-painting, etc), i found that the threads in the block had rusted up, and wouldn't happily take the plug. Kicking myself for not returning it as soon as the block was drained...

Sadly, the accessory drive is right in the way of the plug, and so i can't fit a tap in there. I searched and the shortest tap i could find is about two inches, and wont even come close. I think there's about an inch of clearance in there.

Went to remove the accessory drive, to find that the lower bolt below the pump housing is to rusted to even think of moving. Can't even get a vice grip to sit on the rounded bolt head, looks more like a stove bolt now and than a hex head. I could maybe try to force it, but i'd much rather leave well enough alone there.

So my question is - what are my other options? I cleaned the threads well as i could with a wire brush and pb blaster, and got the plug to seat in about an 1/4 inch, but it's slightly crooked and i know is not seated well in the threads. It threads in okay, but not nearly as well as i would like.

I'm thinking of

A - letting it be and keeping an eye on it. The drain hole is fairly plugged up with corrosion from the inside, and only dribbles water when draining, so there likely won't too much pressure in there to worry about. I don't plan on doing any long sails over the next few months, and can just see how it goes, though ultimately i'd like a solution i can trust a little more.

B - JB weld it shut. It only moderately works as a drain plug anyway, and i'm a liveaboard in a climate where i don't winterize (Seattle), so i doubt i'll ever need to fully drain the block. Plus i plan on switching to fresh water cooling within the next year.

Other options?

Thanks,
steve

[67c&ccorv]

I'd bite the bullet and get that accessory drive sorted out...might as well do it now.

Then you can re-tap the drain plug hole properly.

[marthur]

Would a well lubricated steel pipe plug be hard enough to clean out the rust?

[JOHN COOKSON]

Maybe you can find an expansion plug that would work?
Check in Google. I know they come in many different sizes. I don't know how well they work however.

TRUE GRIT

[Stevenph]

I'll give the accessory drive another shot. I'd rather do it right, I'm just scared to start down another rusty path this late in the game. Excuses excuses...

I think I'll try drill out the bolt enough to get a reverse thread extractor in there. The top bolt didn't seem to be installed with excessive torque, hopefully the lower one just needs a little encouragement.

There are only three two bolts, upper and lower from the water pump side, holding the drive on correct? Then the drive should just slide out forward? Anything else I should be prepared for?

[BunnyPlanet169]

First, do no harm VS Mission Creep

I'm all for doing it right, but ask yourself first: "Is the drain plug the only engine thing that's between me and a functional boat?" If that's true, then I would strongly consider fixing the plug only, and waiting till your season ends, or you have a few months free, to sort out the rest.

You can buy a 1/8NPT tap, grind a ring around the shaft at the top of the threads, snap off the shaft, and use the stub with your fingers, then small pliers or a wrench to clean out the hole. Easy fix, $15.00, and you're boating.

Take the drive off and you'll be worried about re-timing the engine/distributor at a minimum, and maybe opening up many more 'worm cans'.

I personally never use a left handed screw extractors. In my experience, they work basically never, and will more likely leave a hardened tool snapped off in the hole you've drilled.

If you must drill something out, go at it slowly, using LEFT HANDED drill bits. Yes, they're real, and they cut counterclockwise. They will not only create a hole, but will often work the bolt out as you get to the larger sizes.

In this case, you ONLY need to take the head of the bolt off! The casting holes are through holes and the accessory will just push away (maybe helped with a punch on the stubs). Maybe you can grind the head off instead.

With the Accessory out, you can attack the stuck bolt with a vise grip on the shaft.

From the pump-side view, there are only two bolts holding the accessory drive, located approx 12:00 and 6:00. You'll want to get the pump out of the way (bolts at 1:00 and 7:00), and there's a third bolt about 3:00 that's just for the castings that can stay in place.

The pump and accessory bolts are usually difficult to access, rusted, recessed, and you'll be working with your head upside down and over the engine.... There is a great extender bolt from MMI for the lower pump which is worth every penny.

Good luck!

[Stevenph]

Good point.

I already have had the distributor and water pump out and haven't set the timing yet, so that wouldn't be added trouble.

I like the idea of shortening the tap, I'll give that a try. I'd considered it but assumed those bits were manufactured to be so hard as to make cutting them near impossible.

[BunnyPlanet169]

I like the idea of shortening the tap, I'll give that a try. I'd considered it but assumed those bits were manufactured to be so hard as to make cutting them near impossible.

Exactly. Use it to your advantage - they're brittle as a result and fracture fairly easily. Grind a ring around the shaft, and then put the tap across two dowels or something so the middle is unsupported. Give it a sharp rap with a hammer and cold chisel on the ring, and it should break neatly in two. The grind introduces a stress point that the fracture will follow. You only really need to nick it like 0.03" deep, but all the way around.

PS: And if you've got the pump off, then drilling/grinding off the head of the other bolt should be easy too! The lower pump bolt is the worst, so that's great!

[67c&ccorv]

I'll give the accessory drive another shot. I'd rather do it right, I'm just scared to start down another rusty path this late in the game. Excuses excuses...

I think I'll try drill out the bolt enough to get a reverse thread extractor in there. The top bolt didn't seem to be installed with excessive torque, hopefully the lower one just needs a little encouragement.

There are only three two bolts, upper and lower from the water pump side, holding the drive on correct? Then the drive should just slide out forward? Anything else I should be prepared for?

Whatever you do don't use one of those!!!

This forum is full of pages of owners using them - breaking them off in the bolt itself - then not being able to drill the bolt out because of the hardened steel so called "easyout" stuck in the middle of the bolt!

[Easy Rider]

Could you cobble together an extension on to the tap, so it could reach the drain hole? Just checked my spare in the garage and there is about a one inch space between the accessory drive unit and the pulley wheel that would give you a direct shot at the plug hole. You might even be able to make a quick, cheap extension out of a short piece of copper pipe squashed on the end to get a bite on the tap. Just go slow with it. Good luck.

[ndutton]

What am I missing?

I don't understand the difficulty. The drain hole is a straight shot from the side otherwise the long nipple wouldn't fit there. Yeah, it's close to the pulley but it's still clear. My 1/8" NPT tap fits perfectly into a 10mm 12 point socket so with a ratchet and extension this should be a cake walk.

[TomG]

I don't understand the difficulty. The drain hole is a straight shot from the side otherwise the long nipple wouldn't fit there. Yeah, it's close to the pulley but it's still clear. My 1/8" NPT tap fits perfectly into a 10mm 12 point socket so with a ratchet and extension this should be a cake walk.

That's exactly what I was wondering. My aft drain hole has a six-inch brass nipple that extends straight off the block. Like Neil says, it's pretty close to the A-drive, but it's a straight shot nonetheless. I was thinking maybe it's an early model/late model difference so I didn't bring it up, but it is definitely a straight shot on my late model.

[Stevenph]

I'm not sure why, but on mine there is no access, the distributor cylinder is directly in front of the plug. No chance of access whatsoever. I'll send a photo when I can.

[Easy Rider]

Steve,
Just checked my spare A4 again and looking at your picture in the first post and compared to my late model your drain plug hole does indeed look like it is further back than mine. The drain plug on mine, and I suspect on all late models, is directly below the bottom bolt on the water jacket and in the center of the 1 inch clearance between the pulley and the distributor. From your picture, yours looks like it is further back toward the rear of the motor and the block casting around the plug looks like it could be a bit different from a late model. Do you have a real early model? IMHO at this stage, I would stay away from attempting to remove the accessory drive. I think I would approach it by shortening the tap described in an earlier post and having a go at it, especially if the distributor is already off. You will need that drain occasionally, even in Seattle, so try to keep it.

[Stevenph]

It's a very early model, no thermostat, early models of all accessories. In great shape for how old is, has lived in fresh water most of its life.