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Old 23-07-2019, 12:31   #1
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Broke head off bolt.....need advice

Another simple job gone off the rails. This morning I replaced my raw water impeller, the old impeller had lost some bits so I needed to retrieve them. I have always found those bits on the hose side of the cooler, so proceeded to remove the end cap from the cooler assembly. By the way this is a 50 HP Yanmar, 1995, 4JH2E. The end cap is held on by 2 bolts, from the parts manual they are M 8X 25. First bolt I put the wrench on the head comes right off the bolt. I have given the second bolt a tug but am pretty shy now and it seems like it may meet the same fate as the first bolt.
My dilemma, to give perspective we are in Grenada and parts are not quickly accessible.

I am looking for advice on my options

1) I have bought some Liquid Wrench penetrating oil and will attempt to remove second bolt. Should it come out I can remove the end cap exposing the bolt and with vice grips is the bolt likely to come out?

2) The second bolt breaks off, I remove the end cap and remove both bolts with vice grips.

3) I am getting hauled on August the 20th for a bottom job, it is about an hours motoring to get there and they have an on-site diesel mechanic. Does it seem foolish to motor with only one bolt holding the end plate on. If not I could wait until then. I have tested just at anchor and it does not leak at this point.

Bolt question, the manual says the bolts are M 8X 25 plated. Is there anything special about Yanmar bolts? The local Yanmar parts supplier does not have any bolts in stock.

Thanks for any advice Jim
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Old 23-07-2019, 12:41   #2
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Re: Broke head off bolt.....need advice

IS any of the bolt exposed?

1) I would start with penetrating oil. You might need to hit it a few times and wait. The more you use and the longer you wait the better.

2) If you have enough thread exposed use 2 nuts. screw the first one down as far as you can, then screw on the second nut down to the first. Now, using a box wrench, start unscrewing the first nut. It will lock against the second nut and you should be able to back the stud out.

3) If there isn't enough thread to get two nuts on it, try to drill the center of the stud out, then use an Easy Out to try and get it out.
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Old 23-07-2019, 12:46   #3
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Re: Broke head off bolt.....need advice

Yanmar bolts are special.....they’re painted gray.

I’d probably take it all the way apart and back out the bolts with vice grips myself.

M8 isn’t really big, and a little corrosion has likely seized this bolt in there. Too much for the head, but ok for the bolt body to turn.
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Old 23-07-2019, 12:49   #4
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Re: Broke head off bolt.....need advice

Shrew, great tip. If I remove the end cap there will be about 3/8 inch of threads exposed, might just be enough. Thanks
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Old 23-07-2019, 12:52   #5
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Re: Broke head off bolt.....need advice

Sailmonkey, I do have a spray can of Yanmar grey, easy to make the bolts special.
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Old 23-07-2019, 12:59   #6
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Re: Broke head off bolt.....need advice

Quote:
Originally Posted by lovinlifebda View Post
1) I have bought some Liquid Wrench penetrating oil and will attempt to remove second bolt. Should it come out I can remove the end cap exposing the bolt and with vice grips is the bolt likely to come out?

Use penetrating oil on both bolts. Give it time. Apply every hour for a day or two.


You want to rock the bolt back and forth ever so slightly, looser and tighter, until it moves freely. Don't just turn it in one direction.


Will it come out with vise grips? Probably. Maybe not.


Quote:

2) The second bolt breaks off, I remove the end cap and remove both bolts with vice grips.

Apply penetrating oil every hour for a day once the stubs are accessible. Then rock the bolt with the vice grips, don't just turn in one direction.



Quote:
3) I am getting hauled on August the 20th for a bottom job, it is about an hours motoring to get there and they have an on-site diesel mechanic. Does it seem foolish to motor with only one bolt holding the end plate on. If not I could wait until then. I have tested just at anchor and it does not leak at this point.

I wouldn't try it without a plan B. Can you bypass the oil cooler? You might not need it for a relatively brief period of motoring at reduced power.


Quote:

Bolt question, the manual says the bolts are M 8X 25 plated. Is there anything special about Yanmar bolts? The local Yanmar parts supplier does not have any bolts in stock.

They're just like any other M8x25 bolt.
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Old 23-07-2019, 13:02   #7
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Re: Broke head off bolt.....need advice

If you have to end up drilling it make sure you pick up left hand drill bits and extractors. I had this happen with a couple of bolts on my Volvo. Left hand bits were great as they ended up extracting the bolts by themselves eventually.

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Old 23-07-2019, 13:10   #8
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Re: Broke head off bolt.....need advice

Quote:
Originally Posted by lovinlifebda View Post
Another simple job gone off the rails. This morning I replaced my raw water impeller, the old impeller had lost some bits so I needed to retrieve them. I have always found those bits on the hose side of the cooler, so proceeded to remove the end cap from the cooler assembly. By the way this is a 50 HP Yanmar, 1995, 4JH2E. The end cap is held on by 2 bolts, from the parts manual they are M 8X 25. First bolt I put the wrench on the head comes right off the bolt. I have given the second bolt a tug but am pretty shy now and it seems like it may meet the same fate as the first bolt.
My dilemma, to give perspective we are in Grenada and parts are not quickly accessible.

I am looking for advice on my options

1) I have bought some Liquid Wrench penetrating oil and will attempt to remove second bolt. Should it come out I can remove the end cap exposing the bolt and with vice grips is the bolt likely to come out?

2) The second bolt breaks off, I remove the end cap and remove both bolts with vice grips.

3) I am getting hauled on August the 20th for a bottom job, it is about an hours motoring to get there and they have an on-site diesel mechanic. Does it seem foolish to motor with only one bolt holding the end plate on. If not I could wait until then. I have tested just at anchor and it does not leak at this point.

Bolt question, the manual says the bolts are M 8X 25 plated. Is there anything special about Yanmar bolts? The local Yanmar parts supplier does not have any bolts in stock.

Thanks for any advice Jim
You run a risk either way:
  • If you don't touch it all it might start leaking with only one bolt. Halfway there is not a good time to have to start dealing with it. You can reduce the risk by sailing as far as possible. Usually Grenada is in a good wind zone.
  • On the other hand if you try to remove the second bolt to get access to the first, and you fail, then you will have a broken motor, not usable at all. If you do tear into it be sure to follow the advice of others in this forum and apply a good penetrating oil, several times over as long as you can. Many people think PB Blaster is the best.
I broke one of these bolts on my Yanmar, at the other end of the heat exchanger. There was no stub to grab with vice grips. I did successfully drill it and use an easy out to remove it. Obviously the hardest part was keeping the drill bit centered in the bolt and not drilling into the aluminum. Start with a small drill then enlarge the hole once it is in the center of the bolt. In another instance I found a broken head bolt which was down inside the head about 1/2 inch. I used a short piece of pipe as a guide for the drill bit. That job was a cinch except for how hard it was to keep metal filings from falling into the hole and getting into the engine.

You'll have to decide after considering the risks
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Old 23-07-2019, 14:28   #9
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Re: Broke head off bolt.....need advice

Assuming you must drill and have good access to the stub, file the end flat at least enough to do a good center punch first. Don't start with a too small drill bit, lest you break it off, compounding the problem. As note, left hand bits are useful. Careful with easy outs, they can also break.

Patience is you BEST friend.
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Old 23-07-2019, 15:18   #10
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Re: Broke head off bolt.....need advice

This video has some great ideas for removing broken bolts.
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Old 23-07-2019, 17:32   #11
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Broke head off bolt.....need advice

Don’t use an easy out on a seized bolt, I learned that 40 years ago, reason is nothing will drill out an easy out, they are hard as diamond.
Vise grip is your best bet, penetrating oil certainly can’t hurt, but may not penetrate due to the corrosion.
Drilling a hole straight thru the middle does relive tension and helps greatly in extraction, left hand bit if you can get them may walk it right out of your lucky. Try to find cobalt bits, use lots of oil and don’t drill fast, lots of pressure, slow speed and lots of cooling oil.
The current bolt, heat the cap and the bolt head with a propane torch a couple of times letting it cool, try the penetrating oil, then the third time or so try rocking it back and forth, tighten a little loosen a little, object is to get to move a little, back and forth, if you get it to move penetrating oil is much more likely to work as you have broken the corrosion seal, so let it soak over night, heat it in the morning and try some more.
Idea of course and this is hard is to try to apply the force that won’t twist the bolt, stop before it gets to that point.
Yeah, it’s hard to tell, been a mechanic my whole life and I still wring some every now and again.

Oh, and if there is enough bolt left and it doesn’t take much, you can turn it into a straight head screw with a Dremel tool or a hack saw, if you do that, use an impact driver.
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Old 23-07-2019, 17:54   #12
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Re: Broke head off bolt.....need advice

Many people use too small an easy out. It should be almost the size of the bolt.
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Old 23-07-2019, 18:20   #13
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Re: Broke head off bolt.....need advice

Take end plate off, thread nuts on stubs, weld them on, wrench them out
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Old 23-07-2019, 20:06   #14
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Re: Broke head off bolt.....need advice

Quote:
Originally Posted by a64pilot View Post
Don’t use an easy out on a seized bolt, I learned that 40 years ago, reason is nothing will drill out an easy out, they are hard as diamond.
Vise grip is your best bet, penetrating oil certainly can’t hurt, but may not penetrate due to the corrosion.
Totally agree about the danger of using an easy out, but if the bolt is flush, or lower, no stub available, you have little choice.

Keep drilling until you can put in an easyout that is almost the size of the bolt.

And for an end cap on a yanmar heat exchanger, even if you damage the threads in the bolt hole, it will still likely hold, or you can drill it bigger and tap it.
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Old 23-07-2019, 20:26   #15
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Re: Broke head off bolt.....need advice

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Originally Posted by HopCar View Post
This video has some great ideas for removing broken bolts.
I've been using the self centering drill bit/pilot hole guides (for hinges) with left handed drill bits for years now, one of the best tricks i have come across for this problem, i've got a set of 7 or 8 different sizes, they make dealing with this real easy........
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