Thought I would share a quick story regarding something I did that I generally do not recommend - Free handed drilling a broken front engine cover bolt.  Before I jump into it I will say I do not like to mess around when pulling a car apart. I have all sorts of impact and cordless cutting tools, special "secure grip" tools, etc., and techniques I used to get stuff off. My bottom line is I don't want to get bogged down for a length of time with say a broken bolt. 

So... yesterday when I was removing the super nice front engine cover from the running 429 I am parting out, the left lower corner 3/8" water pump bolt that goes thru water pump and front cover to engine snapped off at the head. I thought "OK, That's fine I will  have some bolt shank to grab when I remove the water pump". When I removed the water pump there was a about 1/2" to maybe 5/8" bolt shank exposed and thought "cool, the medium size monkey wrench will probably back that right off". If everything was steel, I would have applied the heat to the bolt 1st, and trying to spray the bolt, which is still 2"+ inside the cover is futile, I went straight for the monkey wrench.  The thing with the monkey wrench is something is going to turn... it will grab what it attaches to. Well the exposed tip turned and broke right off, almost flush with top of front engine cover.  I then thought well maybe the front cover will just slide off the bolt, but with some gentle and then some not so gentle prying, I knew it was seized inside the cover pretty good and really need to drill out or at least weaken the bolt.. and that is where I thought about hollowing it out.

And this is where I did my no-no .. that worked!  It is hard to drill straight free handed and the aluminum covers are like butter if you veer off and hit them with a drill bit .... however, I stared at that broken 3/8" bolt shank and that super nice cover and knew I did not want to wait to get it all off and to a machine shop to have it drilled out, so I took one of my new 1/4" cobalt hard metal drill bits (seen at bottom), loaded it in the DeWalt Cordless drill and placed it up next to the cover and saw it would just barely reach the engine block.  I knew this special drill bit for hardened still bolts would drill straight through the bolt, but knew I needed to be dead on straight. 
After taking a center punch and tapping a center dimple for the drill bit, I took the 1/4" hard metal drill bit and drilled straight thru the center of the bolt, or as best I could, and kept stopping and visualizing the center of the bolt.  The cobalt hard metal bit went thru the hardened bolt pretty fast, and was probably completely thru the center of the bolt in less than 5 minutes.  This made me stop and think about all those times in my youth I had tried to drill thru hardened steel bolts with regular bits only to watch it spin forever and hardly make a dent. For those of you that have used the bits for hardened bolts know the huge difference ... these drill bits are a must if you need to drill thru something like this.

Anyway, after I had gotten to where I thought i was close to the block I stopped, made one last visual line of site look, and plunged the bit the rest of the way. After that, since I had some movement with the front cover as all the other bolts were removed, I gently pried the cover outward and with the bolt hollowed out, it started to slide off the bolt shank. When I removed the front cover I looked at my drilling to make sure I had not damaged anything. While I did not go exactly center thru the bolt I only varied slightly and only ended up close to the edge. I was chuffed that it worked and thought I would share. I wasn't about to let that bolt get the best of me even if it meant breaking my own rule.

Here is the type of drill bit you need in your tool chest if you plan to cut through something harder than wood!

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Good write-up. I feel like I'm constantly dealing with broken bolts no matter how careful I am. I'll definitely be looking for one of those drill bits next time I'm at the hardware store. 

I can remember way back I use to think the Titanium bits were good.. they are basically worthless on hardened steel bolts, and only really good on soft metal, wood, plastics and such. You want to go straight for the Cobalt drill bits for hard steel. I don't even bother with the other types of drill bits now unless they are part of one of those bit sets with Star, Phillips, Allen, etc bits. Speaking of Phillips, I have basically used them for absolutely nothing in terms of new construction the past decade. My entire new house addition floor framing is using T-25 and T-30 Star/Torx screws and HDR power lag screw.  Even for hanging pictures in the house I will use the smaller T15 & T20 long thin screws. As you get older you find out what works and go with it.

Really off topic and a bit of adult humor, when I went to put down the 3/4" sub-floor over the 2x12 floor joists for the floor framing for new addition, I  knew I could use the #8 ring shank nails with my large air impact nailer very quickly, but instead decided I liked the #9 2 3/8" Deckmate T-25 screws I had used for other projects. What I really like about them is they have the knurled shank up top which are spiraled grooves which help pull the screws down in to the wood once the head bottoms out. I couple weeks back went into the house one day after a long session of sub-floor screwing and telling my wife "I do better screwing when my shank is knurled!"  Needless to say she though that was funny and said she would keep that in mind.  So guys, make sure you shanks are knurled and you will screw better! 

Good advice!

As far as keeping a drill square, I have a DeWalt drill with a spirit level that works both vertically and horizontally. I would think other brands offer something similar. It sure helps with keeping the drill square. When drilling horizontally, staying square side to side is not too tricky but the up and down aspect is very difficult without an extra set of eyes so having a little bubble to guide you is a great help.

In this situation, the front of the engine block would have to be plumb for this to be effective.

Ian you last statement nailed it... I am on a slight incline where the car is parked. I think my drill has the level sight but eye'd it and did OK. Just a slight pitch down as I recall. 

I have been using those drill bits and easy outs for many years drilling out bolts with a hand drill on different repairs including my front engine cover and water cross over 

 The Easy outs —-are placed into the hole drilled  in the bolt and allow you to twist the easy out with a wrench ( in the opposite direction the bolt screws in ) and remove the drilled out bolt —-easy !

The front engine covers on our car are a place where it is very easy to be braking a bolt off when trying to remove the cover 

The bolts go deep into the block and are subject to constant heat and cooling that kind of bonds them together 

Do need to use a good deal of caution when working around anything made of aluminum 

It requires a very careful mindset that is acquired from working with that  soft metal 

Many of my Truimph flat track racing motorcycle parts were aluminum that was an education on the subject 

When removing a difficult bolt once it is moving ( cracked ) best to be twisting the bolt right to left as you are removing it to be freeing any debri  located on the thread 

Would an anti seize compound be of any value when reinstalling the front cover for future removal ?

Are there  harder replacement bolts  available that might prevent them from breaking off in the future ?

The front cover bolt braking is a problem many will have to deal with 

Often when the cover is removed there is enough bolt to grab with a vice grips to remove the bolt that way 

It always surprises me how easy a bolt can be removed once you drill it out 


I like the reversible drill bit easy outs. You pick the drill bit end size  based on bolt size and drill into the bolt... setting your reversible drill to counter-clockwise and then inserting the other end of the bit which has a "knurled" end so that when you run the drill, again counter clockwise, it threads into the drilled hole, and turns the bolt out. I just removed a bolt from a water outlet pipe like that the other day. Often works like a charm... but not always. 

Hey..I mentioned Knurled again... it is my term of the day. I think may new saying to counter Tony's "Enjoy" should be "Knurly, Dude!"

I actually think the term E-Z Out is very inaccurate and misleading. "Difficult Out" or "Maybe You'll Get Lucky Out" would be truth in advertising. 

I know they are about the only real option sometimes but seldom are they "E-Z"

Very true ... it depends on if you can get a good bite of the broken bolt/screw, condition of bolt, and other conditions. I've been lucky with them recently. It often requires a bit bigger hole than drill bit end provided, then I slowly let the easy out thread into the hole. The last one with the outlet pipe truly was an easy out.

I think —you have to be a Skate boarder from California to be using ——-Knurly  Dude —in your conversation  LOL !! 


Knurly, Dude!

getting close to the edge was most likely the best end result really.

Good on ya

I thought the same thing... weakened it near the block.



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