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Exhaust Manifold replacement alternative method to drilling

AntonyC

New member
Joined
29 Apr 2019
Messages
24
I wanted to share what worked and what didn't work for me while replacing my exhaust manifold and bolts, and I hope it helps other people taking on this task. My car is a 1999 996 C2.

I have been planning this for quite some time and I researched all the possible forms of attack to remove the exhaust manifold bolts. My plan was to start at least aggressive and work through to most aggressive in the following order:

Prerequisite:

Coat bolt heads in rust remover gel to clean the bolt heads

https://tinyurl.com/y88jta6g
https://tinyurl.com/ycx89umf

Bolt head intact:

1. Penetrating fluid soak and tease out with breaker bar
2. Penetrating fluid soak and impact wrench
3. Penetrating fluid, induction heater, breaker bar
4. Penetrating fluid, freeze release spray, breaker bar

Snapped bolt head

1. stud extractor connected to breaker bar
2. Weld washer and M10 nut and extract with socket and breaker bar
3. Stomski jib and drill

My Bill of Materials for the job:

- Laser stud extractor
- long handle metal picks (remove threads if I had to drill)
- Additional TCT drill bits (stomski only comes with one of each)
- Long TCT drill bits for the end bolts which you won't be able to get straight on using the standard drill bits.
- Stomski jig
- 10pcs Tungsten Carbide Rotary Burrs Set
- Drilling paste
- Nickle anti seize
- High temp Loctite
- Stainless steel studs
- Stainless steel flanged nuts
- Rust remover gel
- Welder (Clarke turbo 150te)
- 0.8 mild steel welding wire
- Welding PPE
- Mini induction heater
- Stainless steel 3 into 1 manifold with gasket kit
- tap and die

Vehicle Prep:

I had the car on axle stands and removed the wheels, if more access is required you can remove bumper etc, but I didn't find this necessary.

What worked and what didn't:

I was hoping for small percentage of the bolts to come out without snapping, this was definitely wishful thinking. All 12 bolts snapped!
I tried all the methods listed above to get the bolt out intact, but nothing seemed to work. I removed the manifolds and I assessed the situation, all the stud were protruding between 4-7mm which meant I have something to work with for the next round of attempted removal! My worst fear would be if they snapped flush, but ill discuss this a bit later.

Using the stud extractor - in short this really did not work for me. It was hard to get a good bit on the stud and if I did, the stud snapped flush to the head.

So, moving on to the next removal method...bring out the welder! I bought this especially for the job. I figured I would have all the options at my disposal, so I didn't have to stop/start the job waiting on tools/parts.

I have no prior welding ability; I have tried once 5 years ago but that was on sheet metal. I have always wanted an excuse to buy one and I researched what I needed for the task. I concluded that I would require a high amp welder so I could get good penetration into the stud and it needed to be gas. I went onto eBay and picked up a Clarke Turbo 150te 2nd hand. It was perfect for the job. I have a classic mini also, so I figured I would get some use on that car in the future. On a side note, make sure you get appropriate PPE when using the welder, without the correct gear you will hurt yourself. I got a good face mask with auto dimmer, so you can see what you're doing prior to welding.

I started on the bench finessing my welding skills by using old bolts and welding washer and then a nut on top of the stud. once I got my skills honed, I unleashed it onto the car.

Welding method:

Before proceeding with welding, make sure you disconnect your battery, otherwise you will wreck your electronics when connecting the welder. Make sure you put the key in and turn the ignition on before disconnecting the battery otherwise the alarm will go off.

Some context: https://www.hagerty.com/media/maintenance-and-tech/welding-on-a-nut-to-remove-a-broken-stud/

Welding puts a lot of heat and current (amps) through the head and bolt, it will break the bond between the threads and the aluminium block. Just remember aluminium shows no sign of heat until it starts to bubble, unlike steel which will glow red.

Welder settings – I used 0.8 mild steel and I had the feed speed lowish and the amps as high as they could go. I wanted to generate as much penetration as possible. Welders vary so do some practises on the work bench first and see what works best for you.

The key to getting a good weld it to have a clean surface, I used a Dremel with a Tungsten Carbide rotary bit to grind and clean the stud surface prior to welding.

I've drawn in paint (apologies for childlike drawing) what worked for me, this was after trying quite a few different methods. If the stud is protruding, I placed a large washer over the stud and welded around the inside circumference of the washer to the stud. This had two benefits; it gets a lot of heat into the stud and it creates a bigger surface area for the nut to be welded onto.

I then added a second washer and followed the same process. I did a few with single washers but when adding a second you really get some heat into the stud. This is what breaks the lock between the bolt thread and the head...lots of heat. After the second washer I put a larger M10 nut on top of the washer and stud and in a circular motion welded the inside of the nut onto the stud. To add some additional strength tacked the washer and nut together as well.

https://tinyurl.com/y8kfx3xz
https://tinyurl.com/y77x38gn

While the nut is cooling, I sprayed some penetrating fluid around the stud, which in theory should via capillary action get sucked up into the threads. I let the nut/stud cool for a couple of minutes and then proceeded to try and undo with a breaker bar and a 6 sided socked (don't use 12 sided). I teased the bolt out by slowly going back and forth adding pressure and releasing it and then adding more penetrating fluid. This sometimes worked first time others it took three to four times to get the bolt out using this method.

What happens when the stud snaps flush or inside the head? This initially worried me, and I thought I would have to resort to drilling if this happened, well I was wrong. Steel weld does not bond to aluminium so you can weld the stud and build up the stud until 10mm proud of the head - see YouTube video: https://youtu.be/cUlJ5f2-FcQ. Let it cool and then proceed with welding the washer and nut method above. This occurred a few times and I was able to successfully remove the stud.
Using the welder, I managed to get all 12 bolts removed from the head, I was pleased with this because I really did not want to drill and risk hitting the water jacket. Plus, I saved myself £350 on the Stomski jig!

Post removal tasks:

After removing the bolts, I chased all the threads with a tap and I clean the mating surface of any debris.

Bolt replacement:

I read some brilliant posts on here regarding bolts vs stud: http://www.911uk.com/viewtopic.php?...ghlight=&sid=90d8e55a23d0f37bc8e0979891bb0383
I won't get into that debate, but I made the decision to go stainless studs with stainless flanged nuts. To prevent the nuts from bonding to the stud I applied some Nickle anti-seize. I secured the studs to the head with high temp Loctite.

Lessons learned:

To list some of the lessons I have learned if I were to complete the task again:
1. Heating the bolt with a mini induction heater will not work, its an aluminium block which essentially is a giant heat sink. You won't get enough heat into the bolt to unlock the threads.
2. Use lots penetrating fluid
3. I wouldn't spend too much time on trying to get the bolts out with heat and penetrating fluid, I wasted a lot of time on this and should have just sheered them all and then moved straight to welding method. This is my personal preference.
4. Freeze release spray was not effective
5. Stud extractor tool didn't work for me.

I really hope this is useful to other people, I wanted to demonstrate there is an alternative to drilling the bolts out. Any questions or advise feel free to message me or comment.

Thanks,

Antony.
 
I had similar misplaced optimism...... 11 snapped :frustrated:

Great write up :thumb:
 
Hi

Thank you for taking the time to write that up. I have done my 993 already, but when I do my 986 I will take your advice and use the welding method.

One question please, how was the welding upside down? I have heard that it can be quite dangerous due to bits of weld falling on you.

All the best

Berni
 
Hi,

Great write up and hats off for having the courage to experiment to find a solution. Being handy has its advantages. :bow:

Do you have any idea about which method (welding or drilling) would be the most time effective? I expect welding... I am just thinking of time in the workshop (since I don't have the skills to follow either method myself if I found myself in this situation). :wink:

Thanks!
 
Excellent informative post, I've pondered all of the options and thought the induction heater would be worth a try, obviously not.

When can you do mine? :lol:
 
Hi

One solution is to take the car to a specialist who removes bolts/studs for a living. There are several out there with extensive reputations. Cost is approx 180 - 200 when I last enquired.

Berni
 
berni29 said:
Hi

Thank you for taking the time to write that up. I have done my 993 already, but when I do my 986 I will take your advice and use the welding method.

One question please, how was the welding upside down? I have heard that it can be quite dangerous due to bits of weld falling on you.

All the best

Berni

Welding on your back you have to protect yourself against any hot debris, i didn't take any risks and used a overalls, my neck covered, welding mask, welding apron and long gloves. As my welding improved, the debris decreased. I was using shielding gas so if you went gasless then i don't know if it would be a bit more messy. I'm sure someone with more experience could answer the question. Just take it slow and do a bit at a time, and build your confidence. The only issue i had was a sore neck and tired arms!
 
GBinSWE said:
Hi,

Great write up and hats off for having the courage to experiment to find a solution. Being handy has its advantages. :bow:

Do you have any idea about which method (welding or drilling) would be the most time effective? I expect welding... I am just thinking of time in the workshop (since I don't have the skills to follow either method myself if I found myself in this situation). :wink:

Thanks!

Thanks, I'm in the opinion drilling is a last resort because of the associated risks if it goes wrong, i wasn't doing as a time saver.

If i were to do it a second time i would would say welding would be marginally quicker, but its probably much of a much-ness. If you're getting it done professionally i would let the technician advise on what they are most confident doing.

I realise i did not really answer your question but i hope it helps.
 
jezgreen911 said:
I had similar misplaced optimism...... 11 snapped :frustrated:

Great write up :thumb:

When all 12 snapped I did have a moment asking myself why i started this job against most peoples advise!

But it was a great learning exercise and the sound of the new manifold definitely makes it worth it!!
 
I know you explored a few different techniques but how long did it take you to remove each manifold?
 
Having done plenty of welding under cars in the past I can attest to it being both difficult and dangerous, with small bits of molten metal burning through clothes and skin no matter how well covered up you are.

When I did my manifold bolts, 10 out of 12 snapped. A stud extractor turned out to just be a way of snapping the studs off flush with the head. I hired a Stomski jig from a fellow forumite for a very reasonable sum and drilled out all the studs and it took two full days, on my back on the drive in the rain. Miserable.
I used new stainless studs and stainless K-nuts (all metal lock nuts to withstand the heat).

If I did this job in the future and was on a budget I wouldn't do anything differently. If I wasn't strapped for cash thenI would happily pay my local professional welder to do the method described by the OP. I reckon they would charge in the region of £200, but they are unusually good on price.
 
Very interesting, would be good to see some pics of the studs you extracted after welding the washers and nuts on to. I'm looking for an excuse to get a welder so maybe this will be it?
 
This reminds me why my manifolds have been in a box in the roof-space for the past three years!
 
Well done!

I'm either going to have to get someone to do this or tackle it myself at some point in the next year or so. I've never had much luck drilling sheared bolts even with left handed cobalt bits. I find the drill goes off centre as often as it works which causes a major issue in aluminium.

I can weld (MIG) well enough but working on such an expensive engine does make me nervous.

I wonder if it's a good approach to take the view all WILL shear so just grind the rusty remains clean and weld an oversized nut on straight off?
 
Great thread, thanks for taking the time to compile all the info and pics. :thumb:

I've been having similar fun and games with my 996 Turbo recently.

The rust had actually corroded right through one of the actuator rods leaving behind just a mess and a non-functioning turbo. (pic 1).

Taking the actuator off simply involves removing 2x 10mm hex head bolts. Only the corrosion has welded them in.

Could get an impact gun on one, which made short work of it, but the second one just would not give up for love nor money. Eventually ended up grinding the head off. Pic 2 is what was left - should be the screwthread of the bolt, is actually just a corroded mess.

Pic 3 are my manifold bolts, which may need to come off to replace the turbo. :(

8kIFWjN.jpg

JETYRAc.jpg

rjkM5U5.jpg
 

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