Broken bolt question

[windshear77]

1985 Mercruiser 140 4 cyl. Engine. Tried to replace the manifold end cap and broke the first bolt. I was thinking manifold bolts would be tough, but I guess the part being so old it was frozen. See photo. Do I need to get a bolt in it right away or can it wait until next Spring to drill it out? Any advice on getting out the other three bolts?
Thx.

 

[Scott06]

Heat them/ the manifold with a torch. Try a left hand drill bit on the broken one after u heat it

 

[harringtondav]

^^^ Same. Heat, and lots of it. Impact driver works best. I start with a hammer driven hand impact driver. If that doesn't work, use an air impact wrench. Best solution for extracting any stubs (from senior forum members) is to weld a nut onto the stub and wrench it off, immediately. The weld heat will overcome any thread resistance.

 

[nola mike]

See if you can get the other 3 out and remove the cap. You may have enough of a stub to get some vise grips on.

 

[Bondo]

Tried to replace the manifold end cap and broke the first bolt.
or can it wait until next Spring to drill it out?

Ayuh,...... Welcome Aboard,........ Why were you replacin' the end-cap,..??

If ya wait til next year, the problem will be worse, 'n probably leakin' water all over the alternator, which is never good,.....

 

[Rick Stephens]

Now that it's broken, you gotta fix it or suffer other issues as Bondo articulated. Being a welder, I almost always think in terms of at least applying a bit of heat or some sort of molten condition of metal. So forgive me for having a one track mind.

Getting the other three bolts out would be easiest with a lot of heat in a short period of time on the head of the bolts. You can use propane, although oxy-acetylene is faster, but has the potential to get to the excess side where metal structure changes. What we are trying to accomplish is to expand the bolt by heating it inside the relatively cooler cast manifold which isn't going to expand as much, then let it cool and shrink back before going at it with an impact wrench. Same when we weld a nut to the end of the broken bolt, this quickly ups the temperature of the bolt inside the cool cast iron manifold, expanding it and breaking up the rust, after it cools the bolt with a nut on it usually comes right out. I use a MIG welder to do this. Can be done with a stick welder or a TIG but is a lot more difficult. With a MIG, point, shoot, remove the bolt. I've even welded a larger nut to the head of a stuck bolt to get even higher heat application directly to the stuck bolt. And a bigger socket to apply torque to.

I do that way before choosing to drill and 'easy' out a bolt. But drilling something is always anathema to a welder.

 

[windshear77]

Thanks for the replies. I'm replacing it because the nipple for the water hose is pretty far gone/ rusted through. I dont' have much equipment so probably go with a propane torch and a reverse drill bit and/or hammer driven hand impact driver.

 

[windshear77]

Torched it, PB Blasted it, reverse drilled it, then Irwin screw extractor broke inside the hole I drilled in the bolt. Any ideas on what do at this point?

 

[kenny nunez]

The suggestions are all good and work. However the smaller the bolt the more difficult. The bottom line here is to really give some thought to replace the manifold before it leaks internally and ruins the engine.
If the replacement cover is exactly shaped like the original It looks like there is enough room on the cap next to the broken bolt to drill and tap another hole. 17/64” bit for a 5/16” x 18. By using a socket head bolt there should be enough room on the flat area of the cover. Cast iron is easy to thread so just take your time and use tapping oil.