85 928

Broke a bolt off removing my water pump. It's so deep in the hole I have to drill it out.

Any advice ?

I'm using a cobalt bit but it's slow going and I feel like I'm making matters worse.
Good thing I'm not a dentist.

 

My suggestions:

1. Use a dremel with a round cutting bit to make sure your "dimple" is centered to the greatest extent possible.
2. Find a couple of good quality reverse twist drill bits.
3. Start with a smaller bit and work your way up to where you can use an extractor.
4. Heat, let cool, soak with Kroil or other high quality penetrating oil. Repeat.
5. Cross fingers, remove with extractor.

 

Mcr,
you could bolt the old water pump housing back on, put a bushing in the hole that the bolt is associated with and use that to help keep the drill centered in the bolt.Depending on how far off-center the current drill hole is, you might have to find a bit that just fits through the hole in the pump casing and use if to re-center the drill hole. (A larger drill bit is more rigid and less likely to deform).
If you don't have something to use for a bush then the large drill trick would at least get you starting in the bolt center.

Myles

 

Yep and then fix it with a time cert.

 

Great idea. Just tried it but the bolt hole is right by the center. The drill goes in at an angle. So close.

 

You could drill out the water pump hole and use these drill stops to center the drill. Then remount the water pump.

 

It looks to me like the broken bolt is not too deep yet. Before it gets there, what I would do is obtain a hex nut that is fairly large but with about the same size thread or hole as the bolt in question, and then put it in you lathe and counter-sink one side of it almost down to the other side. Then place it over the exposed end of the bolt and with your MIG welder weld the nut to the end of the bolt by "squirting" the wire electrod at a fairly high power down into the opening and weld the nut to the bolt. Then when it cools a little turn the bolt out.

 

I've been in this exact situation. Go to a hardware store and buy a small bushing with an OD equal to the hole size and an ID the drill bit size. Put the drill into the bushing. That will keep the bit centered. Works great. You'll probably have to drill out.the whole broken bolt and destroy the threads in the housing. But then just use a Helicoil. I've used them many times over the years. They are fantastic. Good luck.

This is basically the same as Kevin in Atlanta is saying. But a hardware store should have enough brass bushings to match your needs exactly if the drill stops don't. You could also make your own from a dowel of aluminum, steel, or brass. But you should be able to find the right bushing.

 

Here are a couple of videos you might find useful:

 

^^^Those vids are great, but in reality, doing it on the bench is a huge difference from doing the hole in the front of the engine still in the car.