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IanG1
Silverstone


Joined: 08 Jan 2016
Posts: 127



PostPosted: Sun Mar 24, 2019 7:04 pm    Post subject: Broken rear caliper bolt Reply with quote

After sorting my rear brakes out on the drivers side now rebuilt with new disc, pads and handbrake shoes started the near side today. Bottom caliper bolt was a bit tight but breaker bar and working it a bit and it came out. Moved onto the top bolt and again ubber tight but breaker bar cracked it and managed a few very tight turns till it went solid. Got my even longer breaker bar out but snap the head came clean off. I managed to get the caliper off by unplugging the ABS plug and removing the connector to give me enough to get it over the broken bolt. Next tool came out my stud extractor, heated the base of the stud I had left and cranked on the extractor and again it moved half a turn an thought that was it then snap it breaks clean off level with the hub. At this point it was time to walk away and have a brew. I now need to some how remove whats left in the hub by drilling out and helicoil hopefully without the hastle of removing the hub. Anyone had the same problem before and can offer some pointers or advise.
Cheers
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16369
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Sun Mar 24, 2019 7:18 pm    Post subject: Reply with quote

Heating the stud would've made it tighter until it cooled down again. If you can get a drill down the centre around 8mm it will relieve some of the pressure. You've then chance of hammering something in that hole that will get a grip (like a torx bit) and possibly let you unwind it out. Or better still a stud extractor like so:

https://www.toolstation.com/screw-bolt-extractor-set/p51010


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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6783
Location: Brighton


PostPosted: Sun Mar 24, 2019 7:57 pm    Post subject: Reply with quote

If you have a stud extractor snapped off then even i would be looking at removing the hub and sending it to an engineer to sort out .. need some pretty dam good drills to get that out imho .. someone like Alex here is worth his weight in gold sorting this kinda problem .

Its beyond me .. that's for sure .
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James M-S
Suzuka


Joined: 11 Apr 2017
Posts: 1012
Location: Derbyshire

2009 Porsche 997 Carrera 2

PostPosted: Sun Mar 24, 2019 8:06 pm    Post subject: Reply with quote

Sorry to hear this Ian, even more gutting with this weather, Mad

at least it will be properly sorted by the summer. Driving

I’ll ask around for who can fix it locally.
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kurlykris
Indianapolis


Joined: 30 Jun 2014
Posts: 2447
Location: Warwickshire


PostPosted: Sun Mar 24, 2019 8:47 pm    Post subject: Reply with quote

Try and get some penetrating fluid/Plusgas down the threads, keep giving it a bit more every half an hour or so for a few hours, then as Alex says drill a hole down the centre, start off with say 3mm, then keep opening up to about 8mm ( I think it is an M12 thread/stud) then hammer a Torx bit into the hole, more plusgas and gently tease it backwards and forwards and keep adding plusgas, it will come out eventually. You could also try heating the hub with a blowtorch, then cooling it with water, muliple times, keep going with the Plusgas as you do it Thumb

When contemplating jobs like this on my cars I always plan ahead and give all fixings a few doses of plusgas over a few days prior to starting work on the car, obviously you can`t really do that with the caliper bolts due to the length, but it really does make life easier Grin
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wasz
Sepang


Joined: 28 Dec 2012
Posts: 2933


1999 Porsche 996 Carrera 2

PostPosted: Mon Mar 25, 2019 9:11 am    Post subject: Reply with quote

Just whip it off and take it to a local proper engineer (like Alex) and have it mounted in the mill and drilled out / thread cleaned.

You will be out there for hours swearing at it otherwise.

Or just pick one up from a breakers.

e.g. https://www.ebay.co.uk/itm/1999-Porsche-911-996-3-4-Near-Side-Left-Rear-Hub/123461984486?epid=13025362413&hash=item1cbee860e6:g:bIAAAOSwB5lb2du9&frcectupt=true

for £60 not worth faffing.
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James M-S
Suzuka


Joined: 11 Apr 2017
Posts: 1012
Location: Derbyshire

2009 Porsche 997 Carrera 2

PostPosted: Mon Mar 25, 2019 3:57 pm    Post subject: Reply with quote

Agree

Unless you can spark erode/ EDM it out Dont know
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BillCoupe98
Newbie


Joined: 11 Dec 2016
Posts: 28
Location: South West


PostPosted: Mon Mar 25, 2019 7:23 pm    Post subject: Reply with quote

You cant have much thread sticking out the back of the hub mount now. Can you try driling out the centre with some cobalt drills from toolstation, 3 mm, 5mm, 6.5mm and then tap the 6.5mm hole with an 8mm tap, screw a short 8mm allen bolt into the caliper bolt and tighten it into the broken stud so it goes through the hub and falls out the back
 
  
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IanG1
Silverstone


Joined: 08 Jan 2016
Posts: 127



PostPosted: Mon Mar 25, 2019 7:49 pm    Post subject: Reply with quote

Thanks for all the replies, all helpful cheers.
Bit of an update, my biggest fear was drilling central and square as top of broken stud wasn't flat so difficult to centre punch. Decided to make a drill guide by cutting down one of the old bolts the same length as the depth of the caliper mount holes then drilling down the centre of it on a pillar drill so nice and square. I then mounted the caliper back on one fixing and nipped it up and packed a bit of tape around my new guide to take out any play then into the top hole. Used my air drill as its compact and low speed and drilled down the guide with a 3mm drill into the remainder of the snapped bolt. I am now as far as a 5mm drill right through the bolt so not sure whether to try an extractor or to tap it 8mm and try and wind it through as BillCoupe98 suggest, I have heated and cooled and will pick up some plusgas tomorrow as only have wd40 which aint the best for this stuff. So far so good but not rushing it. Worst case I end up with a helicoil or a second hub if it goes pear shaped but never been beaten by a car in over 30 years of spannering and not going to give up without a fight LOL
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16369
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Mon Mar 25, 2019 7:54 pm    Post subject: Reply with quote

thumbsup

Your on the right track.

WD-40, although not the best at this, is excellent stuff and worth letting it soak in it until you get some plus gas.
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6783
Location: Brighton


PostPosted: Mon Mar 25, 2019 7:56 pm    Post subject: Reply with quote

My hat off to you Sir .. i know my limits and this sort of thing is beyond mine .. and i fix these cars for a living .. sigh .
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IanG1
Silverstone


Joined: 08 Jan 2016
Posts: 127



PostPosted: Mon Mar 25, 2019 8:21 pm    Post subject: Reply with quote

deMort wrote:
My hat off to you Sir .. i know my limits and this sort of thing is beyond mine .. and i fix these cars for a living .. sigh .


LOL cheers pal, I think its from being a tight git who never gives in but also learnt when to walk away and have a brew and think about things, Amazing things can be done in a home garage with a bit of thinking outside the box. It still might go Pete Tong but drilling a hole down the centre was my biggest obstacle, the rest just takes patience. Good job it isn't my daily though
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16369
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Mon Mar 25, 2019 8:56 pm    Post subject: Reply with quote

IanG1 wrote:
Good job it isn't my daily though


I'm sure you could've got by with one caliper bolt in for a couple of days Grin
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Paynewright
Monza


Joined: 17 Apr 2018
Posts: 189
Location: Nr Lutterworth Leics


PostPosted: Mon Mar 25, 2019 9:50 pm    Post subject: Reply with quote

I wouldnt go near it with a screw extractor - they are brittle and the challenge moves up several levels when they snap off in the hub!

I would research the drill size to get within a few thou of the bottom of the bolt threads so you can peel out the remaining thread - this is how the Stomski jig works for exhaust bolts. It might be a random imperial size!

Good work so far!! Well done.

Ian
 
  
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Paynewright
Monza


Joined: 17 Apr 2018
Posts: 189
Location: Nr Lutterworth Leics


PostPosted: Mon Mar 25, 2019 9:56 pm    Post subject: Reply with quote

Just checking an old bolt - 10mm is pretty close to the thread valley diameter - maybe go 9.5 and see how you get on
 
  
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IanG1
Silverstone


Joined: 08 Jan 2016
Posts: 127



PostPosted: Tue Mar 26, 2019 8:35 pm    Post subject: Reply with quote

Well had to bite the bullet and for the sake of sanity I've bought the second hand hub quoted above. It's just not shifting which ever way I try and despite my best efforts my drilling is slightly off centre when viewed from the inner side so will struggle to drill out without damaging the aluminium. For £54 (I got £6 discount at checkout for some reason) delivered it's a no brainer, all the mounting bolts have cracked loose, just got to back off the hub nut and split the ball joints.
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MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7068
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Tue Mar 26, 2019 9:20 pm    Post subject: Reply with quote

It is a pain to have to do that, but given the time and cost it could involve I don't blame you. Fronts are even cheaper than rears for the C2 as there are so many boxster parts around.

MC
 
  
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kurlykris
Indianapolis


Joined: 30 Jun 2014
Posts: 2447
Location: Warwickshire


PostPosted: Tue Mar 26, 2019 10:14 pm    Post subject: Reply with quote

Booooo, so close to getting the end result too Grin

On to the next quandry then, some people say you should replace the caliper bolts every time you remove them due to stretching/stress, the new ones come, apparently, with a coating of retaining compound on them to a: stop them from coming loose and b: stop them siezing in the threads Thumb

Given that Porsche fixings of all kinds seem to be made from Mickey Mouse Metal, I tend to give them a blob of loctite "bearing retainer" when I put them back in, this is a very low strength loctite and will hopefully help stop the thread corrosion and keep moisture out in future Laughing
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16369
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Tue Mar 26, 2019 10:18 pm    Post subject: Reply with quote

My rear caliper bolts have been in and out more times than a groom's holiday tackle on the wedding night. I've never got that 'stretch bolt' thing. Totally pointless.
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kurlykris
Indianapolis


Joined: 30 Jun 2014
Posts: 2447
Location: Warwickshire


PostPosted: Tue Mar 26, 2019 10:29 pm    Post subject: Reply with quote

alex yates wrote:
My rear caliper bolts have been in and out more times than a groom's holiday tackle on the wedding night. I've never got that 'stretch bolt' thing. Totally pointless.


To be fair, it does happen, I obviously have to deal with it in my job quite often on bolts that have been highly stressed for 15-20 years and they simply let go Sad

I think using the old bolts on a cars calipers a couple of times is fine, but I make sure I use a retaining fluid to try and minimise corrosion to make future work less of a pain in the butt Grin

In fact I`m shocked at how bad the fixing bolts on modern Porsche cars are, I`ve never seen anything like it in 30 years of tinkering with cars nooo
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