Broken drill bit in cylinder head.

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StuInHorwich

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Hi, thanks for reading this first post on LandyZone. I appear to be in a bit too deep for my liking and experience now and would like some advice.

I have come into possession a 1994 Discovery 1 that is need of some TLC. It's history was murky and when I decided to change the spark plugs I twisted one off. A local garage suggested I either replace the head or drill what was left of the spark plug then fit a helicoil. I opted for the latter but while drilling out the plug, increasing the diameter 1mm at a time, the drill jammed and snapped a piece off the end of the bit. I managed to fish a piece out with a magnet on a string but when I started the engine to flush out any swarf the engine clunked. I stopped the engine straight away but now it won't start at all. I fear that there is another piece of drill bit in there that has fallen to the bottom and has now jammed against the crankshaft.

What advice does anyone have for my next move? I'm sure it will now involve taking the head off but what then? Can you access the bottom of the cylinder? What work and costs will be involved putting it all back together again. Is the landy saleable in this state?

All ideas welcome.

Many thanks
 
You'd have a hard time for it the jam the crankshaft unless you have a hole in the piston?

Plus if there was swarf in the cylinder you could have ****ed the bore by running it.

Do you have much mechanical experience? Unless you do sounds like you should quit now! Someone will buy it off you for a small sum
 
:eek::eek::eek::eek::eek:

Dude, that really doesn't sound good.

Firstly, dont start it again.

Presuamably you left the head on the engine when drilling it? That's a big mistake. Engines need to be totally clean inside, even a tiny piece of grit in the cylinder bores can destroy an engine. Filling it with swarf certainly will kill it and pieces of hardended drill bit is even worse.

Also, there's no such thing as flushing swarf out of an engine. There is only microwelding the pistons to the cylinder bores and grinding bits off the pistons, cylinder bores and possibly the valves as well.

The crank isn't the problem. If the engine is seized (which you can test by putting a big spanner or socket and turning it by hand) your problem is in the bores.

Please dont take this the wrong way as I mean no offence, but it sounds like you lack basic mechanical knowledge of engines. I'd say stop messing around with it, and get a mechanic. I think you've already killed the engine, but if it can be saved you'll need someone to take it apart to diagnose what damage has been done.
 
Thanks Martyc and Mundungus. Nope, I'm not very experienced, this is all new for me but learning every minute. I'd been advised to try drilling out the old plug so a helicoil tap could be inserted. This was preferable to removing and replacing the head. (Out of my league.) I was to guard against swarf going in by using grease and any bits would be blown out anyway. I never counted on the drill bit snagging and breaking and now I've ended up with a knackered engine.

I suppose I should just work out whether I'd lose less money by fixing it, then selling a running vehicle, or getting someone to pick it up from my house for next to nowt. It's got some decent bits on it too!
 
StuInHorwich said:
Thanks Martyc and Mundungus. Nope, I'm not very experienced, this is all new for me but learning every minute. I'd been advised to try drilling out the old plug so a helicoil tap could be inserted. This was preferable to removing and replacing the head. (Out of my league.) I was to guard against swarf going in by using grease and any bits would be blown out anyway. I never counted on the drill bit snagging and breaking and now I've ended up with a knackered engine.

I suppose I should just work out whether I'd lose less money by fixing it, then selling a running vehicle, or getting someone to pick it up from my house for next to nowt. It's got some decent bits on it too!
Click to expand...

I would advise breaking it and try and get as much money back as possible.

Or post some pics on here and highest offer wins!
 
StuInHorwich said:
but when I started the engine to flush out any swarf the engine clunked. I stopped the engine straight away but now it won't start at all.
Click to expand...


**** me, no!!

First off, never work drill bit sizes up in 1mm steps, recipe for disaster. You drill a pilot hole the size of the tiny flat bit at the tip of the final size drill then go straight in with that, do not **** about with it, drills were not meant to cut 1mm at a time.

Head should be OFF the engine, you will need a decent drill press/mill to run a drill big enough for a sparkplug helicoil, its a big drill bit.

You now have swarf in there, a bit of drill and maybe a hole in the piston or a bent rod and maybe a valve or two.

The head needs to come off and before anything else is done.
 
I'd have interpreted the advice differently.

You'd been advised to drill it out and fit a helicoil because this is cheaper than replacing the head. Either way the head had to come off I'd have thought.

Even had the drill not broken, risking getting swarf in the cylinder is a bad idea.

Blowing it out implies that the all of the bits of swarf would have to pass through the exhaust valve opening. This runs the risk of damaging the valve and valve seat, or even worse getting stuck and stopping the valve from closing. On many engines, this could cause the piston to hit the valve and break it.

Your first post suggests that you think its possible for the swarf and drill bits to pass by the piston and drop down to the crank. This isn't correct. The whole purpose of the piston and piston rings are to form as close to an air tight seal with the walls of the cylinder bores as possible. And these things are hot and are rubbing together at a rapid rate as the piston goes up and down. The last thing you then want is tiny pieces of metal scraping down the sides (which is where your piece of drill bit probably is). This would scrape chunks out of the bores and/or piston.

As I said before, you really need a mechanic to diagnose the damage. I wouldn't advise taking the head off yourself.
 
lazydog said:
Sorry to be thick but undoing a spark plug from a ali head a sparkplug broke ?
Click to expand...
I have never ever broken the metal part of a spark plug in any kind of cylinder head! sometimes you lose the porcelain but a plug in an alloy head? What kind of treatment has this engine had before the OP got involved? Surely the threads would strip before the plug actually broke?
 
Last edited:
waldershelf said:
I have never ever broken the metal part of a spark plug in any kind of cylinder head! sometimes you lose the poreclain but a plug in an alloy head? What kind of treatment has this engine had before the OP got involved? Surely the threads would strip before the plug actually broke?
Click to expand...
Never done a Ford Ka with ford spark plugs then they nearly always snap.
 
StuInHorwich said:
I'd been advised to try drilling out the old plug so a helicoil tap could be inserted. This was preferable to removing and replacing the head. (Out of my league.)
Click to expand...

If you've got the skill to drill and helicoil a plug thread with the head in-situ then you should have the ability to remove the head and do it on a bench I would say :)
 
oldskool said:
Never done a Ford Ka with ford spark plugs then they nearly always snap.
Click to expand...

ill second that the original glow plugs in astra td's are bastards fer snapping and the ones in transits aswell but a spark plug only once as the last place it got serviced they put the plugs in with an air gun and sheared the fooker off

only thing to do is use a reverse tap pigtail and prey it comes out failing that drill the entire fooker out with the head off and re-tap the plug hole :D:D
 
A garage advising to drill and tap with the head in situ speaks volumes for THEIR technical ability.
I think the expression is - Name and Shame.
 
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