snapped thermostat housing bolt

[menostig]

Help. So another routine job goes pear-shaped. One thermostat housing bolt was reluctant but WD40 freed-it and out it came. The other just sheared despite WD40. I've removed the thermostat housing and what I'm left with now is the bottom half of this bolt sticking up out of the inlet manifold by about 1mm. How to fix this ?

cheers
Roger.

[YIIHAA]

Drill a small hole in the bolt then use an extractor, like this
[url]www.machinemart.co.uk/product.asp?p=040213526[/url]

[YIIHAA]

Unless there is enough protruding to get purchase on it with some mole grips. (unlikely if it is really only protruding by 1mm)

[BliarOut]

I would try to rotate it with a dot punch before you start eating away at the metal. Good soaking with WD first, then use a sharp dot punch and a small hammer to turn it. Success will depend on whether it sheared because it was tight against the housing or because it's stuck in the threads.

[menostig]

Thanks !

I know it's impossible to say, but what are the chances I can reuse the thread ? Perhaps I will have to chase/tap/die or something it ?

cheers
Roger.

[BliarOut]

menostig said:

Thanks ! I know it's impossible to say, but what are the chances I can reuse the thread ? Perhaps I will have to chase/tap/die or something it ? cheers Roger.

The dot punch method (if it works) will leave the thread perfectly intact without any damage.

[YIIHAA]

BliarOut said:

The dot punch method (if it works) will leave the thread perfectly intact without any damage.

The extractors should leave the thread intact as well, provided you drill an accurately centered hole and don't dive straight in with the largest ectractor.

[davefiddes]

Hmm. Sounds like the steel bolt and the ali manifold have reacted together. Try putting release oil onto it on a regular basis for several days....but othewise leave it alone. It'll take a while but it will soak down the threads. Then I think you'll have to use a thread extractor. Copperease or similar will make it less likely to happen again.

[BliarOut]

YIIHAA said:

BliarOut said: The dot punch method (if it works) will leave the thread perfectly intact without any damage. The extractors should leave the thread intact as well, provided you drill an accurately centered hole and don't dive straight in with the largest ectractor.

But the dot punch method still leaves you that choice in the event of it not working

Add to that the risk of a poor quality extractor snapping (Not uncommon when you're first using them as they're brittle). Ideally the hole should be tapered too for maximum purchase with the extractor. It may well work, but it's a riskier strategy IMO.

I have a preference for leaving as much of the parent material intact as I can and using an extractor as a last resort. If one breaks you're pretty much committed to the spark erosion route which is a pain.

Good soak with penetrating oil, tap the remainder of the thread gently to shock it and then dot punch it. Another method is to carefully chisel a flat slot and try a screwdriver. Failing that, then reach for the extractor.

[eliot]

It's only on the inlet manifold at the end of the day. Worst case is remove it and get it machined out.

[steve_D]

Whilst the dot punch method will work on a bolt that has sheared due to being overtightened I think in this case it is corroded into the hole.
I would:
1. Flood the remains with WD40.
2. Hit the end of the bolt a few times to attempt to break the seal the corrosion has created.
3. Drill a 2mm hole down the middle of the bolt until it breaks out into the space below the bolt i.e. the bottom of the hole in the housing.
4. Fill that hole with WD40 and leave for a day to soak.
5. Hit it again.
6. Use the 'easyout' extractor already mentioned.
7. If that fails to move it then place a nut over the bit of bolt and weld the bolt to the inside of the nut. Attempt to undo the bolt whilst the whole lot is still hot.

Good luck
Steve

[cortina1]

hello,

I have had similar problems, worked out by letting the stub soak in WD40 overnight and then drilling hole and using left hand screw extractor as mentioned in some of the other mails. the bigger extractor you use will give you more leverage, make your pilot hole a safe size not as to damage the threads by a wonky hole etc and buy some quality extractor to prevent snapping. You could do this method if tapping out with a punch did not work.