Sheared bolt on 1gm10 yanmar - how to remove?

[Helvic hunter]

I had a small oil leak from my Yanmar engine at the weekend where the seawater pump attaches to the engine block. I duly tightened up the three bolts but must have used too much force on one and it sheared the head of bolt plus approx 6 mm of thread. Did not remove water pump, went for my first sail of the season, no oil leaking yet! What is the best way to remove the remnant of the bolt that is in the engine block?

Regards

Helvic hunter

 

[Nicholas123]

It depends how much thread you have got left protruding,I am not familiar with the engine.
I would remove the pump & file some flats on the stud to fit a spanner.Gently heat the block & let it cool down with a blow lamp a few times to free the stud adding a bit of diesel & letting it soak in over night in the hope that it would penetrate & ease removal.I hope this helps.

 

[Tranona]

Tricky one, that. The (mild steel) bolt goes through the bronze pump housing and a tube in the aluminium front cover then itno the cast iron blcok. Lovely cocktail of metals if the pump leaks! Usually it is the head that goes, not the thread, but think the only way of getting at the threaded bit is to take the whole front cover off. Quite a major task, and you may still have to drill out the remains of the bolt in the crankcase. Are you sure it is the bolt holding the pump in and not the ones holding the front cover onto the pump? The big bolts are (from memory) either M7 or 8 , pretty difficult to break just with a spanner.

 

[Avocet]

Depends what access is like. Is the thickness of the pump flange the 6mm, or is it now 6mm below the surface of the "parent" metal? As it snapped when you were tightening, it might not actually be seized. I'd be inclined to either take the pump off (if that you enable you to get some Mole grips on the end of the projecting part) or if not, try drilling into the back of it and using an "E-Z out" (those coarse left-hand threaded stud extractors). I don't have much faith in them usually, but if the bolt wasn't seized, they could work.

 

[Helvic hunter]

No, it is the M6/M7 bolt that attaches the pump to the engine block, not the 7mm bolt that attaches the plate over the impeller pump. I did not realise that the Al plate can be removed - what is involved in that?

Helvic hunter

 

[Scareyclott]

This site might help you identify the rouge bolt and what it actually holds in

http://www.soverel33.com/Boat/Engine/Forward/Content.html

Some of it is still under construction but there are plenty of usefull diagramms on the bottom of the "General" section

Scott

 

[Tranona]

Depends what access is like. Is the thickness of the pump flange the 6mm, or is it now 6mm below the surface of the "parent" metal? As it snapped when you were tightening, it might not actually be seized. I'd be inclined to either take the pump off (if that you enable you to get some Mole grips on the end of the projecting part) or if not, try drilling into the back of it and using an "E-Z out" (those coarse left-hand threaded stud extractors). I don't have much faith in them usually, but if the bolt wasn't seized, they could work.

Problem, as I explained above is that the threaded bit is not in the casting that the pump is attached to, but goes through a tube about 35mm long into the cast iron crankcase behind. So even if you take the pump off you will not access the thread. That is partly why I asked exactly which bolt it is that is sheared as there are 3 small ones holding the face plate onto the pump housing.

 

[robertj]

dont try any heath robinson methods as if you do have to get expert advice they will charge an arm and a leg to recover the situation.

Buy a set of threaded stud extractors, they are basically a screw taper similar to a tap but with a left hand thread (unscrew to screw in) you drill the stud and then screw in the taper stud/bolt extractor of the right size, when it reaches its maximum you keep turning and the stud will start to extract out.

sorry if thats not explained very well.

bob

 

[robertj]

Depends what access is like. Is the thickness of the pump flange the 6mm, or is it now 6mm below the surface of the "parent" metal? As it snapped when you were tightening, it might not actually be seized. I'd be inclined to either take the pump off (if that you enable you to get some Mole grips on the end of the projecting part) or if not, try drilling into the back of it and using an "E-Z out" (those coarse left-hand threaded stud extractors). I don't have much faith in them usually, but if the bolt wasn't seized, they could work.

lol

didnt see your thread

bob

 

[PuffTheMagicDragon]

If all else fails, there is one method - albeit a savage one - that has never failed.

Get an ordinary arc welder and fit a thickish electrode, around 3mm or so. Set the amps to not very high, take careful aim and then strike the protruding end of the sheared bolt. The aim is not to strike an arc but just to strike the bolt material with the live electrode. Since there is not enough power for an arc the electrode will (should) stick to the bolt and quickly get very hot. At this stage unclip the electrode from the tongs. The heat from the short-circuit will have heated the bolt remnant in its hole, causing it to expand slightly. Let it cool. Bend the remnant of the ruined electrode at right angles and use it like a 'handle' to rotate the bolt.

You do need a good aim and a steady hand but this is not too difficult if you bring the gap down to a few millimetres before making the final prod with the tip. Downside is that it is difficult to avoid getting a flash but this will not be a serious one.

Desperate situations require desperate solutions sometimes. Good luck!

 

[Tranona]

Desperate situations require desperate solutions sometimes. Good luck!

But, he still has to dismantle the whole of the front of the engine, removing the crankshaft pulley, water pump, injector pump, governer, front timing cover to get at the broken bit in the crankcase. If you have ever done it on this engine you will appreciate it is probably an engine out job to deal with it on the bench. (Guess how I know).

 

[PuffTheMagicDragon]

But, he still has to dismantle the whole of the front of the engine, removing the crankshaft pulley, water pump, injector pump, governer, front timing cover to get at the broken bit in the crankcase. If you have ever done it on this engine you will appreciate it is probably an engine out job to deal with it on the bench. (Guess how I know).

No, I have never done it on that engine. I have re-read carefully your posts #3 and #7. If the situation is as you describe so clearly then, yes, I agree that my method would be very difficult to manage on site. My reason for suggesting it was after the recommendations to use Ezy-Out bits - never an 'easy' job on a small diameter, especially when one uses cheap imitations instead of the proper tools.

My mistake. Thanks for your explanation.