Disaster strikes again..

[JonB]

Hi all

A couple of days ago I discovered a coolant leak at the thermostat housing on my +2. Quick call to Sue for a replacement and I'm out there undoing the bolts, when this happens:

Sheared off bolt head due to rust.

So after a brief interlude of fun, the car is off the road again.

I have tried to use my stud extractor but it cannot get a grip - same with the mole grips. While I consider my options I have put some penetrating oil on it.

I think there are a couple of things left to try. Some heat cool cycles. A special extractor (has opposite thread and you drill the bolt and wind it in, then keep turning) or try to weld a nut to it, then use a socket. As it is part of the precious cylinder head, I need to be very careful.

Thoughts?

Cheers
JonB

[pauljones]

Jon

Heat and freeze spray, plus be VERY carefull.

You could try drilling it out with ever increasing sizes till it breaks the rust seal. Then tap set to clean threads.

Another option. File flats onto it and get a socket on it.

Cut a slot in it to get a long screw driver in it. Use its length for torque.

New head

[RogerFrench]

The first thing I'd recommend is to ditch your easy-out or whatever kind of left-hand thread extractor you have. I have seen many of those broken off in a stud or bolt, making the situation worse.
I have a small Stillson-type wrench which would grip that, but I wouldn't use it straight away.
I'd apply a good penetrating oil, not ordinary WD40. Not sure what's available in UK nowadays, sorry. Then give a few sharp raps with a hammer to the broken-off end, then try to grip and remove, turning one way then the other. Patience is needed!
Heat is great if you can apply it to the end, like with a small jet in a gas welder.
If you definitely cannot find something to grip it, welding a nut is your best bet.

[USA64]

I'd plug that hole for starters. I've had success with Easy-Out but I am also very patient.

[69S4]

Another vote for dropping a nut over it and welding. The heat will help loosen the "stud" and you'll be able to turn it. Even if the weld breaks you'll only be back to square one.

Not been your few months really.

[bitsobrits]

If you go the welding route, you will want to be very thoughtful about how to properly ground the stud if using MIG/TIG welding. Attaching the ground clamp to the alloy head may yield unexpected results.

I would favor the filing of flats to use a small socket combined with localized heat from a propane torch (not enough heat to melt alloy).

[JonB]

Guess I won't be using the "easy out" thing. I've had one snap on me, and success with another, but this is the cylinder head we're talking about so I will be careful.

I have plenty of proper rust penetrating oil (as well as the home made acetone/ATF mix), thanks to the seized front suspension spindle. I've sprayed some around the bolt and left it. Access with a long handled wrench is tricky as it is occluded by higher parts of the engine (the head itself and the brake servo unit).

This all feels so familiar. I tried to weld a nut onto the suspension spindle but it didn't take. Whether that is down to my welder or me I do not know. However, as the cylinder head is aluminium and the bolt steel, I have hopes that it will require less torque to undo. At the point of shear it was pretty well rusted through.

Re: Welding - not sure about the grounding. I can't attach the ground to the stud itself as it is too short. You think perhaps that the contact area between head and stud won't carry the current?

I think I will try filing it first. Maybe with a Dremel... but I need to be careful to take the minimum off it, otherwise it may shear again, nearer to the head. If that happens there will be no choice other than to drill it out.

[JonB]

This is interesting: https://www.youtube.com/watch?v=cUlJ5f2-FcQ

Upshot of it is to connect a charged 12v battery to the end of the stud and the cylinder head, and the current makes the stud get really hot. This breaks down the rust bond and allows you to use a wrench to remove the stud without damage to the aluminium thread.

[vincereynard]

Tell you what Jon - you try it first.

Be very careful with the welding. I've done this before, the heat can alter the bolt to the strength of toffee and all that happens is it shears off flush with the head.

Make a epoxy tunnel around the stud so you can fill it with release agent. Then just leave it alone apart from giving it an occasional sideways tap.

[JonB]

Ha, ha, Vince - sharp as a pin as usual! Nice one!

There is another option if everything fails - drill it out and tap a bigger thread, then fit a reducer.

[JonB]

Hmm, another look at it. I was able to fit a washer and wind a new nut onto it. Should be easy to puddle weld the top of the stud, hopefully without getting it too hot. Need to get some gas though, I'm out. Probably why I couldn't weld the nut to the suspension spindle (could have sworn I heard the gas hissing.. oh well..).

I did try the 12v battery trick but it didn't heat the stud much at all, it just made the wires really hot.

On the plus side, I found a pair of brand new bolts in my spare bolt pack (bought from some eBay seller for too much money, only to find they are UNF and I needed UNC) that are the correct thread / length for when I put it back together.

Meanwhile it is soaking in releasing fluid!

[alan.barker]

I would wedge a nut on the broken part and puddle weld.
If you decide to drill out then first make a drilling jig that will just slide over the broken screw shank.
Then the drilling jig can be clamped in place to guide and keep your twist drill central.
Once drilled out remove jig and use a Helicoil Kit which includes a pilot drill the correct dia for the Helicoil Tap.
This will return it to the original dia and in fact stronger than original.
The Helicoil Kit will come in handy if you have problems with any of the Exhaust Studs stripping
Alan

[JonB]

Oh no, don't mention exhaust studs, Alan! Asking for trouble. I'm afraid to even sneeze in their general direction.

So yes, what about this: I've wound a nut onto it. How about drilling little pilot holes where the thread is and putting in self tappers to wedge the nut into place on the stud? Kid of like the way the rear hub pins work.

Edit: Oooh by the way, you'll perhaps notice from the picture that the cooling system full of water. I thought it had a proper water / anti-freeze mix but nooooo...! So I will put that right toutes suite!

[Mick6186]

In 47 years of working on cars the best broken stud extractor I have ever used is a kit supplied by Snap-On. The kit contains different size drills to suit the stud size. You use the appropriate size bit to drill down the centre of the stud then gently hammer in the supplied correct sized splined octagonal spring steel rod. A special nut slides onto the rod then you simply unscrew the broken stud. I have used this tool to extract some seriously tight/rusted broken studs,
Mick

[JohnP]

there is an excellent stud removal forum here....

https://app.aws.org/forum/topic_show.pl?tid=9543

It even has a useful title so people can search for it.