Read this:  kukko bolt extractors.pdf

Gedore 8551-1 8551-2 8551 3 8551 4 8551 5 8551 6 8551 7 8551 8
  M 3 - M 6 M 6 - M 8 M 8 - M 11 M 11 - M 14 M 14 - M 18 M 18 - M 24 M 24 - M 33 M 33 - M 45
Wrench size (mm) 2,7 2,8 4,9 7,0 9,0 12,0 14,5 18,0
Length (mm) 50 57 65 70 80 85 95 100
Weight (g) 4 9 13 30 50 100 150 290
Drill (mm) 1,8 2,6 3,7 5,5 7,0 10,3 13,7 18,6
Part number 8551-1 8551-2 8551 3  8551 4  8551 5 8551 6 8551 7 8551 8
EAN mumber 4010886675847 4010886675854 4010886675861 4010886675878 4010886675885 4010886675908 4010886675915 4010886675939
Code number 6758490 6758570 6758650 6758730 6758810 6759030 6759110 6759380
Screw outside diam AF 1/8-1/4 1/4-5/16  5/16-7/16  7/16-9/16 9/16-3/4 3/4-1 1-1.3/8 1.3/8-1.3/4 
Screw outside diam mm M 3 - M 6 M 6 - M 8 M 8 - M 11 M 11 - M 14 M 14 - M 18 M 18 - M 24 M 24 - M 33 M 33 - M 45



Hey Jay:

I saw this old post, I just broke the bottom H20 pump bolt (!), should I be concerned about the depth of the thread for that bolt. How deep can I drill?

Your solution of drill and tap with next size bolt is a good one.


Dave Petry 1984 Euro 928S

You can drill to the depth of the original hole without any trouble. Get a drill bit that fits the nearest good hole and mark this depth with masking tape or a collar. Then transfer that to the correct size drill bit and make your new pilot hole. You have to be REAL careful not to stray off of the existing bolt. Use a dremel to make a nice flat spot and then make a sharp center punch on the flat. Then start with really small bits and work up. If you do that right you might even get the bolt out before making a mess. Brad Orr (wonder what happened to him lately) suggested doing these steps with a series of left handed drill bits and the act of doing it might just kick the slug out. I had made a big mess before that suggestion so that wasn't an option for me.

Good Luck!!!!! Drill straight in!!!!!!

Jay Kempf


At 03:15 PM 11/11/01 -0500, Jay wrote:
> Brad Orr (wonder what happened to him lately) suggested doing these steps with a series of left handed drill bits and the act of doing it might just kick the slug out.

Indeed I did. Left hand bits are THE answer for this problem. If done properly, they offer the absolute highest potential of removing the
broken fastener and leaving the original female threads intact. I have had to do this literally hundreds of times over too many years.
Dave, if you haven't attempted surgery yet and want more specifics let me know.

Brad Orr



Just take the undoing of the bolts really easy and slow. If there is any feeling of unusual tightness, try undo a little, then tighten a little, back and forth, gently, slowly, no rush....
This will frequently get a corroded bolt out with minimum risk of breakage.
Maybe a tap inwards on the head with a small hammer will also help to break the grip of the corrosion - just a few light taps, some penetrating spray wont hurt either.

I had one of my water pump bolts break off, leaving about 3/8" sticking out of the block. A few sprays of WD40, tap with a hammer, do something else, tap again, grab with vise grips, and out it came.

Before fitting new pump, clean all the threads with a plug tap, also CAREFULLY, slowly, with lubrication - you don't want to break a tap off in there, they are HARD!
Good luck,
83 S


The key to centering on a bolt is using a small pilot drill first -  much less than an 1/8 inch. The hole in the pump is much too large to  allow for centering such a small drill. A bushing made of harder metal inserted into the water pump bolt hole should be accurate enough to center the drill. The guide if long enough would also guarantee the  correct angle. The guide could also be used for a center punch to  start the pilot drill. The trick in drilling out any broken bolt is getting the pilot hole centered.

You were lucky to get the bolt out that was broken. Often the threads  fuse and the resistance is more than the strength of the bolt itself.
In these cases an easy out is useless and the only chance is drilling the thing out.

A three drill regimen is probably the best. A very small drill for a  pilot, a bigger drill to accommodate an easy out and the third drill the size required by a tap. Re-tapping the hole is not a perfect solution but probably good enough for most cases. Only one bushing
should be needed as once the pilot is straight the rest of the drills  should track, but additional bushing would only improve the job.

Finally, I find a 90 degree offset air drill the easiest to use in  these cases. It is small, light, fast and can be adjusted for speed by
varying air pressure.

Dan the Pod Guy
Portia's Parts


An improvement is to use a left-hand drill bit for the second and third tries. It is surprising how often the broken bolt will back itself out.

Harbor Freight strikes again!

Wally Plumley
928 Specialists

At 01:15 AM 3/11/2005, Dan Brindle wrote:
>I have heard of left handed monkey wrenches but not drills.

Not common, but available - Harbor Freight has a set.



You are only partially correct on the use of cold to loosen the bolts - indeed, the aluminum has a higher contraction coefficient than steel, and the aluminum will shrink more than the steel. When that happens, however, the bolt hole gets LARGER, not smaller - which is why they come out relatively easily.