My first time WP/TB job and I 'only' broke 1 bolt! Now I have to remove it. In all the post I've read so far, most people don't have much luck drilling the bolt out. I've tried it with broken bolts on R/C airplane engines a few times and once it even worked. My plan of attack on this is: soak it in PB Blaster (done); spray it with 'freeze-off" (done); PB Blaster again; heat the bolt with the propane torch; try acetone/ATF; freeze it again with dry ice this time; soak with acetone/ATF again, then the vice grips. If the vice-grips don't work, maybe I can heat the bolt up and pound a nut driver socket on it and turn it with that (?) If it comes down that I absolutely have to drill it out, I think I'll go like this: Go to my local R/C shop and get some brass tubing that fits snug on a 6mm bolt, then get the next 2 smaller size tubing to nest inside the 6mm~ I.D tubing. Make a drill centering jig long enough that I can't drill through the end of the bolt by silver soldering the tubing together and cutting to the right length. I have left-handed drills and a battery drill that can run slow. I'll grind the end flat with my Dremel before I start. I REALLY don't want to chew up the WP gasket surface much less the block. The bolt I broke is in the web area between the cylinder head passage and the impeller area. (see picture) One post I read here seemed to indicate that seeing as the bolts are torqued to just 11 ft/Lb, they mostly hold the water pump in place, (?) so one missing bolt is not a big deal. It just serves as a pin to help locate the gasket. (??) As the broken bolt in not on the perimeter of the pump, will it being broken affect the operation of the pump or is it 'Porsche (over)Engineering' at work(?) Help on this is greatly appreciated.

 

You do want to remove it and replace it. I do not subscribe to the theory that since there are many bolts with low torque, missing one won't be a problem.
I went through this too, but my broken one was in the top center, and difficult to get to. You need to create a jig, so that you drill straight. Be careful of ovalling the hole. I did that, and it created more problems (all fixed now however).
Here's my experience: https://rennlist.com/forums/928-foru...t-or-stud.html

 

get a welder,
fit a nut over the bolt and weld it ,
then unscrew it.

NOTE this works well as the welding heat makes the block expand.
The welding wont stick to aluminum.

when heating the block make sure the coolant has been drained out ,
as it will prevent the heat from expanding the block.

If your using a torch you want to use a MAPP gas ,
its the yellow cylinder it heats hotter faster, compared to propane

 

The other thing to note, from the thread I linked to, if you drill out the screw, as Greg Brown said, it is critical that you get all of the old screw threads out as well. So long as the hole isn't dmaged, you may want to chase it with a tap, just to make sure.
Keep a steady hand and you'll be fine!

 

there are a lot of 928s running around missing a water pump bolt.....not that it is right. Some "professional" mechanics doing a job at flat rate book time do take short cuts especially when they know the car owner will never see it...

 

nice mod on the block water pump impeller surface..... who did that for you ?? what a great idea someone had here with that mod... wasn't that greg brown's idea?

 

I hate to confess that my engine has a new WP itted by the PO, but also a broken stud. Engine is out of he car or one years now. Should I? I like to classify this as "don't fix it if it isn't broken". But in fact it is broken!

 

That's why I like to do all work myself. Especially in Thailand.

 

with the engine out, there is no good reason not to address it properly.

 

A few years ago we kicked around the idea of having a drill plate, a piece of metal with holes drilled to line up with each hole. Then fit a drill bushing (hardened steel) in the hole over the broken bolt to keep the drill lined up perfectly. The bolts are 6mm, so it might be tough to find the perfect drill bushing with 1-1.5mm walls through the hole.

If you are replacing the water pump anyway, you won't mind drilling the casting to hold a proper drill bushing.

 

Sorry to mislead, but that pic IS from Greg Brown's repair post that I had on hand. My problem looks like this. I'm SOOOO glad the water pump didn't chew up the block when the bearing failed.

 

Sounds like a plan. to 50/50 acetone/atf. Highly recommended by them as are highly respected. Maybe CO2 from a cylinder instead of dry ice, just b/c of its immediacy and "pointability."

 

All you said to do + firm tapping on the end eventually got mine loose.
jp 83 Euro S AT 56k

 

Thanks for all the help. I welded a nut on the end and it came out easily.

 

Glad it worked I suggest top use Loctite non setting PTFE pipe thread sealant on your new WP bolts this will keep the bolts from corroding in the block