Exhaust stud bolts again!!

[topradio]

I know this is a topic that's been done to death and I have read most of the threads on the subject and they have made me delay replacing my fast disintegrating exhaust headers. However the time has come to tackle the job & I have some questions before I jump in.

1. What is the best way to remove the bolts from the block reducing the chance of breaking them? I have read that heating up the bolts with an induction heater will help, but wouldn't this just cause the bolt to expand and make the problem worse or does it work because the co-efficient of expansion of aluminium is greater than steel?  

2. I have resigned myself to the fact that some of the bolts will probably break in which case what's the best solution. Should I drill out the old studs and simply re-tap the hole with the same thread, if I do this is there a chance that the new thread will clash with the old one and just cause a mess? Should I drill out the hole oversize and fit a Helicoil insert. On the subject of drilling out the old studs, I can't drill straight for toffee and I did read that somebody used an old header cut down to make a template to keep the drill in the right place. I am thinking of using a second similar template mounted an inch or two above the first as a guide to keep the drill square to the job. Any tips from you guys who have tackled the job and did any body remove all the bolts without them breaking.

3. What headers should I go for, obviously not a stock one as the simply rot. Is there a good quality aftermarket one that will interface to the existing cats keeping the system looking stock from outside. Also should I use SS or even brass bolts to make future maintenance easier.

[map]

47 minutes ago, topradio said:

3. What headers should I go for, obviously not a stock one as the simply rot. Is there a good quality aftermarket one that will interface to the existing cats keeping the system looking stock from outside. Also should I use SS or even brass bolts to make future maintenance easier.

Two parts to this:

Headers - I used CarGraphic - there will be cries of "too expensive, go to eBay" or the like but they survived close on 10 years, year round use and in excess of 80,000miles in that time.  The whole CarGraphic system has been added to my stash as it's still good for further use.  The other, cheaper options have good reports so worth looking into folks' recommendations for them.

Replacement Header Bolts/Nuts - as part of the new engine build I sourced motorsport grade Ti bolts and matched nuts which should avoid the corrosion problem and make future work easier.  This is an upgrade that is often used with 99xTT exhaust refits/upgrades so should be fine on my ol' 986.  As with my approach to Headers there are cheaper approaches and they're valid too. 

[Greenman]

Never done this myself but I remember @Nobbie making some form of guide/template to aid in straight drilling.   I also believe there is a commercially available jig you can buy/rent to help. Hopefully Nobbie will chip in with some advice.

[Boxob]

No experience but from reading:

1 leave it to the professionals; if not then

2 lots of penetrating oil applied over an extended period;

3 tighten first, then back off and repeat;

4 use rattle gun to shock and break seal;

5 heat bolts then shock with ice spray (don't know correct terminology) to break seal (then use 3&4 above);

6 If a bolt shears it might be possible to weld a nut to the remaining bit of bolt;

7 replace bolts with studs and nuts;

8 keep car mobile in case you have to revert to 1!

Whilst the bolts are a known weakness I wasn't aware the headers themselves were an issue. They're often on eBay s/h so not all disintegrate.

 

 

[Nobbie]

First off, I assume you've read the excellent advice on exhaust manifold bolts from @Indi9xx on this thread

I got the cheap eBay SS ones and am very happy with them, the only issues are that on the passenger side you need to protect the P/S pipe with heat wrap as the new headers are bigger. Also I had to remove the rear undertray as the manifolds fouled on it. They also hang slightly lower, so will be the first thing that hits if you ground at the back.

This is the jig I made up to ensure I drilled straight using the cut down manifolds with M8 bushings as spacers which allow M8 bolts to attach it firmly to the head assuming you manage to remove at least two bolts. I also had M7 bushes for when drilling out the bolts as you need a 6.9mm jobber drill to make holes suitable for the M8 tap.

I worried about tapping through the original thread, but it didn't seem to be an issue as the steel seems to have fused with the head. Access is tricky on the end bolts and I had to remove the thermostat housing to drill properly. I made up my own drilling fluid from oil detergent and water and used it regularly to keep the drill temp down.

I wouldn't go straight to helicoils as that leaves you at a bit of a dead end if it goes wrong. Doing it again I would get a MAPP torch to really get some heat into the studs alternated with freeze spray and smacking what's left of the bolt to try and shock it free before attempting to unscrew. I bought a stud extractor, but it was useless. If I had a welder I would have welded a nut to the top of the studs, as it was I dremmeled flats on the side of the bolt shaft and used a spanner. I had to drill out 3 on one side and five on the other including all four at the ends🙁. 

I used standard steel exhaust studs off eBay together with brass nuts. Didn't fancy using SS studs in case I ever needed to drill them out again. The key to this job is to have patience and take it stage by stage without closing off any avenues prematurely such as jumping straight to helicoils.

Let me know if you needed any more info. Good luck.

 

[topradio]

That's all good info guys, its useful to know the sort of problems I am likely to encounter before I start. I have always worked on my own cars and tend to be pretty handy so I'm happy to have a go at this. I have owned my 986 since new and for the first 5 years or so I used an OPC and then for the next 10 a good indi but since then I've done my own servicing and its pretty straightforward if you take it easy and use a logical approach.

Fortunately as the car is now very much a garage queen I have the time to leave it on stands and go and have as many cups of coffee as I like while contemplating my next move.

@Nobbie that's exactly the sort of jig I had in mind, is it available for hire? 

ps. I've only found that stud extractors make the job 10 times worse.

[Nobbie]

41 minutes ago, topradio said:

That's all good info guys, its useful to know the sort of problems I am likely to encounter before I start. I have always worked on my own cars and tend to be pretty handy so I'm happy to have a go at this. I have owned my 986 since new and for the first 5 years or so I used an OPC and then for the next 10 a good indi but since then I've done my own servicing and its pretty straightforward if you take it easy and use a logical approach.

Fortunately as the car is now very much a garage queen I have the time to leave it on stands and go and have as many cups of coffee as I like while contemplating my next move.

@Nobbie that's exactly the sort of jig I had in mind, is it available for hire? 

ps. I've only found that stud extractors make the job 10 times worse.

Sounds like you've got the right attitude and time to do this. Mine was on axle stands for a couple of weeks as I worked through my options. Happy to lend out the jig for the price of postage. It weighs 2.3kg, so not sure what the best postage option is. If you want I can include the unused helicoils set and M8 tap and then just pay me for the helicoils set if you use it, otherwise just return it it all when you've finished. I would send the 6.9mm drills, but although I only used one for the exhaust studs, both were buggered getting the rear droplinks out😡.

These are what I bought

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F183034379363

and these are the studs/nuts, just realised they are copper not brass. I was a bit worried about pulling the studs out so reasoned the copper would probably give first.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F182290624950

 

[entdgc]

IMHO This is the best read on the topic...

 

[edc]

I've used the eBay manifolds on both my Boxsters. Current car ones been on since 2013. 

[topradio]

Thanks for all the advice guys especially for@entdgc link which I hadn't spotted before - very useful. The car goes for MOT next week so I won't be tackling it until it has a new ticket. Also many thanks to @Nobbie for the generous offer, I'm hopping that by following @Indi9xx tips I won't be doing any drilling but I'll let you know.

I'm also looking at replacing the clutch while I have some of the back end off so I may be back for more advice. I will take some pictures if anybody is interested.

[entdgc]

I would definitely be interested in hearing/seeing how you get on with the manifold bolts as I suspect they may be around the corner for me!

[topradio]

35 minutes ago, entdgc said:

I would definitely be interested in hearing/seeing how you get on with the manifold bolts as I suspect they may be around the corner for me!

I did take a look at them recently and while the manifolds are severely rotten, the bolt heads look to be in surprisingly good condition with only surface rust and the heads are sharp and well defined.  I will be taking my time and using all the tips in your link.

[myfirstboxster]

When i did my manifolds I warmed the engine up and the bolts came out no bother , and i mean warmed the engine , my reasoning was that the aluminium heads would expand faster than the steel bolts , might be a complete load of shyate but it worked for me .   

[½cwt]

On 8/12/2019 at 12:50 PM, myfirstboxster said:

When i did my manifolds I warmed the engine up and the bolts came out no bother , and i mean warmed the engine , my reasoning was that the aluminium heads would expand faster than the steel bolts , might be a complete load of shyate but it worked for me .   

There is a degree of logic to this.  Always better to heat up the female part of a thread to expand it more than the bolt or stud that runs through the centre.  Only if you are trying to heat shock to break corrosion or sealant it the part you apply the heat to a bit less relevant.  Not sure how you'd work out when the heads were warmer than the bolts and it would all equalise pretty quickly I imagine as it is not localised application of heat.

[EXY]

IIRC Revolution use a specialist company to pop in and winkle them out, I suspect the Revolution boys are pretty handy with the spanners so food for thought?

[topradio]

2 minutes ago, EXY said:

IIRC Revolution use a specialist company to pop in and winkle them out, I suspect the Revolution boys are pretty handy with the spanners so food for thought?

Thanks, I have this in my back pocket as a backup plan. What I'm going to do is carefully tackle all the bolts to see how they go and if I really start running into problems I can put it back together while the car is still drivable. The worst case would be to have a disabled car in the garage with no means of moving it. 

[EXY]

17 minutes ago, topradio said:

Thanks, I have this in my back pocket as a backup plan. What I'm going to do is carefully tackle all the bolts to see how they go and if I really start running into problems I can put it back together while the car is still drivable. The worst case would be to have a disabled car in the garage with no means of moving it. 

I would be mildly curious to hear it without an exhaust  

FWIW I didn't break any on our 986 when I removed the manifolds to fit a set of those SS equal length manifolds/headers, have to say I am not a fan of the SS Manifolds.

I have a set of standard manifolds from a MY04 2.7 on ebay if they would be of interest.

https://www.ebay.co.uk/itm/323882799342

https://www.ebay.co.uk/itm/323882799923

Good luck and fingers crossed for you