Exhaust bolt stripped on head!

[Mr Bean]

Shock horror! While diagnosing low temperature gauge reading on my 1988 2.1 DJ WBX my helper noticed a gap under the head of an exhaust bolt on the RH rear cylinder head. He was only supposed to be reading the gauge while I wiggled the wires but I suppose he done me a favour. Anyway having cured the low reading by remaking the connector I moved on the the exhaust bolt:
In theory the bolt should not have been touched since I had the engine rebuilt and re-installed under warranty many moons ago. I have never noticed it loose or had reason to try it for tightness. However a few turns of the bolt met with no resistance revealed what appears to be a stripped thread. Although I guess the bolt could be broken some way down. Hopefully not for obvious reasons...
Assuming a simple stripped thread the obvious choice would appear to be to Helicoil. But surprisingly of all multifariously varied stuff I have done I have never installed a Helicoil!
I can't be the first to suffer this irritating problem so a call for advice:
What thread would it be?
Can it be done in situ?
What tools will be required?
Can I purchase a kit?
Cheers
CS

[itchyfeet]

Standard M8x 1.25 thread
hole is 25mm deep a 2D (16mm long) helicoil is what you need
buy a kit it will come with the right drill, tap and insertion tool ( you may need to buy the 2D length seperate from the kit)
most can be done in situ as long as you remove enough to get the drill in, you always drill metal very slowly so battery drill is needed.
that part of exhaust has to come off obviously because you are drilling bigger than m8
If you have to drill out a stud don't drill too deep

plenty of youtube vids I'm sure on how to tap a thread and install a helicoil if you never did it.

[Mr Bean]

Wow! I didn't think I'd have to saw the head in half!
Only jazeing.
That seems to be all the info I need especially the depth of the hole which could cause problems if overdone. If insufficient access for electric drill I am sure I can rig something up.Thanks for that.
To be honest I have avoided working on the head fixings of the exhaust for just that reason and so it could have been stripped way back when I had the engine rebuilt and installed. Lets hope no more threads strip when disassembling. I have an important trip this weekend and so will not disturb anything until back.
Best regards
CS

[itchyfeet]

youcan buy 90 deg chuck adapters for a drill.

[Dazco]

I had to use one of these the other day for opening an oil way inside a turbine shaft. Great bit of kit. May be possible to hire one

[itchyfeet]

hardly worth hiring one...
http://www.ebay.co.uk/itm/3-8-Right-Ang ... SwnNBXWMfx" onclick="window.open(this.href);return false;

[Mr Bean]

hardly worth hiring one...
http://www.ebay.co.uk/itm/3-8-Right-Ang ... SwnNBXWMfx" onclick="window.open(this.href);return false;

I have one on order. I do have a converted angle grinder but it lacks a certain level of finesse and requires to be operated wearing welding gloves and safety glasses preferably by a third party!
Cheers
CS

[kevcorks]

With regard to removing the remaining bolts I found the best thing is heat. Lots and lots of it!

I've just replaced my exhaust, and was very worried about removing these studs as i've heard horror stories about it.

I started by cleaning anu exposed corrosion off with a wire brush or similar then a liberal coating of penetrating fluid and leave to soak in. You need penetrating releasant, not WD40, something like Unilease (which I used) or Plus Gas.

After this had been left for a while, I kept spraying mine over the course of a couple of hours as I was on with other things, I got the blow torch out. Now these aren't the best for directing heat, an aceteline torch would be better, so just be careful what is around the area and remove/protect anything that could get damaged. I used sheets of tinfoil folded over until it was a stiff sheet, like an A4 cardboard sheet. I used this to place behind where I was aiming to dissipate the heat.

After the bolt was hot, not quite cherry red but almost, I again sprayed the penetrating fluid on liberally. Now the first couple will gas off due to the heat, don't get a lungful, but once the temperature decreases enough the fluid will stay. As the metals have expanded/contracted some of this fluid will be drawn into the threads by capillary action.

After this I used a ratchet and and a shock tap released the nut and I was able to wind out by hand. Some of the nuts will come off and sometimes the stud, but I managed all 8 of mine like this with no trouble at all.

Hope this helps.

Kev

[Mr Bean]

Strangely enough I have bolts and have never really noticed this in my nine years of ownership
Similar process will probably work and my method has been to arc weld over a nut and wiggle with ring spanner. I might consider heating the head of the bolt with my TIG welder set low. I daresay the job will grow in the usual way...
Cheers
CS