Broken bolt in thermostat housing

[Douglasdzaster]

Definitely going to do something for the man. I’ll find out what he drinks or likes to eat.
The guys at the parts house here saved me a ton by helping me out one day. The next morning I showed up with breakfast.

 

[Pappy]

A Permatex aviation gasket sealer is one of the best out there.
Also, Get a teflon based lubricant for the bolts. Something like Tef-Gel. You will never ever have an issue removing a bolt lubricated with that.
Use this on any bolt that sees salt water. Water pump bolts, gearcase attachment bolts, thermo housing bolts, etc.

 

[RaisedByWolves]

You will get a recess for a screwdriver…., I think you will have no problems unscrewing it.

Thing is, if the bolt is so corroded in there that you snapped the head off of a stainless hex bolt, a screwdriver won’t do any better.

Those parts have become one and only drilling, grinding or melting will get them out.

 

[DaleH]

TIPs for drilling into stainless steels ...

• Have a helper with a spray bottle of water and have them constantly spraying the drill bit ... you will drill thru 3-5X faster!
  ...
• You'll save your drill bit. I only use cobalt drills
  ...
• Also remember that SS work hardens, it doesn't like high speeds (RPMs) and low/light feeds (push or tool advance), so use medium RPMs and push without breaking the bit, you need to cut aggressively - look for chips to break into pieces
  ...
• As with any other drilling effort, make SURE to stop periodically and clear the metal chips - the #1 source of heat and dulling your bit

 

[Pappy]

One more tip on drilling out SS bolts. As Dale mentioned above SS cold work hardens. This means if you hit it with a hammer, bend it, drill it, etc it hardens immediately. SS is a soft metal other wise.
On drilling. First off think about what I just said about the metal. This is why you have to use a hard drill bit such as Cobalt and use a LOT of pressure and a low RPM. You want that bit going through the metal before it hardens ahead of the tool (bit).
As far as the drill bit goes I do not use a small bit first. I use a large bit first! Use a center punch to get a center on the bolt and use the large bit to get a crater formed into the center of the bolt then use a bit that will get you to the bottom of the bolt or however far you want or need to drill. Less bit breakage.

Broken bolt removal and heat.
Almost all of the time you can remove an exposed corroded bolt by heat. What you are doing with the heat is melting the corrosion. It takes a LOT of heat to do this and you do not have a lot of time to work with the bolt when you remove the heat source. This is where most folks run in to trouble. When the heat source is removed the metal casting around the bolt cools rapidly and the corrosion sets up again. You really only have 15-30 seconds to work until you have to apply heat again. You may only get the bolt to move a fraction of a turn at first. Stop.....and apply heat again then resume.
When applying heat you will have to get the casting around the bolt hot enough, EVERY TIME, to burn the paint off the casting plus more..........!!!!
Remember this next time you remove a corroded bolt and you will eventually get pretty good at it.

 

[wmk0002]

There were some GREAT ideas in this YouTube video!

https://www.youtube.com/watch?v=dJfkCj3FWBs

I need some of those lathed out fasteners! Pretty cool.

I have a project Mercury 25 with low compression on one cylinder and I am about to tear it down and see if its scored or if the chrome plating can be salvaged by removing the aluminum transfer. But before I got into that I found that the thermostat cover had a bolt also broken off but it sheared off down in the hole. I am terrible at getting my pilot hole centered but it didnt shear off very deep so I may be able to use a larger drill bit like pappy said and have good results. I probably need to invest in some left handed cobalt bits.

 

[airshot]

Interesting reading on the broken bolts, as a retired toolmaker of 50 years I thought I might add a trick or two of my own. On top of all the ideas posted, I didnt see anyone mention left handed drill bits. I bought a set of these many years back, as they drill they are attempting to loosen and back out the broken screw. The vibration from cutting loosens all but the most stubborn bolts and they typically just grab and unscrew themselves. Left handed drill bit set was one of my better investments in tools. The most difficult part about using them is to remember to run the drill backwards !!!!

 

[RaisedByWolves]

I need some of those lathed out fasteners! Pretty cool.

Turned/bored out/drilled out, “lathed” is not a thing.

Sorry, pet peeve of mine.

 

[RaisedByWolves]

Interesting reading on the broken bolts, as a retired toolmaker of 50 years I thought I might add a trick or two of my own.

Fellow toolmaker here, see pet peeve above. :x

My tip, don’t bother with the spiral flute screw extractors, their junk.

Get a set of proto or proto style extractors and thank me later.

https://www.protoindustrial.com/en/industrial-tools/Proto/Specialty-Tools/Extractors/462d2844-86ec-4bf3-9c71-615db7e14b76_Proto%C2%AE-Screw-Extractors/

Used properly these won’t break and the sharp square cutting edge bites only as hard as you bang it in so it doesn’t expand the bolt threads into the hole further binding it when you turn it.

Another benefit is these are resharpenable if you have access to a belt sander.

 

[airshot]

Thanks but I rarely have to use the extractors, normally the left hand drills take them right out. When the drill gets the bolt hot it usually breaks loose as long as it has plenty of penetrating oil !!!
However your correct, most extractors are junk, my extractor set comes with left hand drills and quality extractors, cant think of the name but they were expensive!! Had that set for 25 years nothing has ever broke!!

 

[C&K]

I've never seen where broken studs or bolts come out of aluminum castings with any consistency by heating. We have exhaust manifold studs break all time in aircraft engine cylinder barrels. When one breaks, put a zip disc in an angle grinder, cut the protruding part of the stud off so it's flush and flat, drill it out and tap it. If you end up ruining the original threads in the hole, loctite a heli coil into it.

 

[airshot]

Dropped it off this morning. He even commended me for not waiting until I broke the bolt off and a drill bit or 2 inside. Just waiting on a phone call. This is the first thing I haven’t done to the boat myself. Drive way sure is looking empty right now.

Smart move, a smart man knows when to let the pros take over !!Let us know how it goes....