Coil pack bolts sheared off

[G-996]

So I've now replaced the 9 'non-siezed" coil pack bolts with new ones, using an appropriate anti-sieze paste.

That still leaves the remaining 3 siezed ones to remove. It's probably an engine-out job to get sufficient access, and my Indy Porsche maintainer has suggested getting an engineering shop to remove the stuck bolts using spark erosion. I've googled this to get a basic understanding of how the process works. Does anyone have an experience of using this process to remove siezed bolts from an engine? I had expected them to removed by drilling, retapping and potentially a time sert or helicoil.

 

[mikeeb]

It really shouldn't be more that a drill out/helicoil job

 

[Luddite]

Drilling out can be no easy task, especially when in situ..?

I have seen attempts at drilling steel fixings out of alloy that have gone wrong, even with the unit firmly mounted in a pillar drill and the drill bit moving off centre (flexing) due to the angle left on the sheared bolt....! if the process is continued then the hole is off centre which might not matter in some locations, though in the case of mounting coil packs..?

As for Copperslip, as has been typed it has been proven to work over a period of time in this location, and no one can tyed of it failing to work in the same location over time... Then Copperslip potentially looks better than nothing.. :?:

 

[martin t]

So I've now replaced the 9 'non-siezed" coil pack bolts with new ones, using an appropriate anti-sieze paste.

That still leaves the remaining 3 siezed ones to remove. It's probably an engine-out job to get sufficient access, and my Indy Porsche maintainer has suggested getting an engineering shop to remove the stuck bolts using spark erosion. I've googled this to get a basic understanding of how the process works. Does anyone have an experience of using this process to remove siezed bolts from an engine? I had expected them to removed by drilling, retapping and potentially a time sert or helicoil.

To paraphrase the Indy 'we don't want to do it'

As long as the coil pack is in place and doing it's job, probably best to leave well alone.

If ever you need to drop the engine then that is the time to tackle those 3 siezed bolts. As has been mentioned, if the worst happens the one just drills a slightly larger hole and inserts a helicoil.

This is the one I have used, it is a complete kit https://www.ebay.co.uk/itm/144647317629?hash=item21ada6e87d:g:CZ4AAOSwpr9i0Z9D

And this is a kit with many different sizes but without the drill/tap and insertion tool.
https://www.ebay.co.uk/itm/403780729837?hash=item5e0334fbed:g:zy0AAOSwC~Zi03s8

 

[deMort]

If both coil bolts snapped then there is nothing to retain it .. to be fair though .. the tension of the coil in the tube will hold it in place ..

A story .. we had a car that another garage had refused to remove the bolts as they were seized .. these were stainless steel bolts .. why i must say would you fit stainless into ally with no grease but that's what i had ..

I could feel they were going to snap and got the service advisor to check with the customer before i proceeded .. as he said .. i need new plugs so i don't have a choice ..

11 / 12 snapped .. i changed the plugs and pushed the coils back in .. as far as i know there have been no issues .. 5 out of the six are Not secure .

When it comes to drilling out .. hell i'm no expert here .. my colleague tends to do this but i have tried in the past to drill out a similar fixing .. as you can see from the image .. you have a thin protruding tube the bolt goes into ..

On my attempt .. with very little pressure .. i was letting the drill bit do the work .. this tube split . I couldn't do anything at that point ..

Now whilst some people might be able to drill these out or use spark erosion .. that's more for caliper brake nipples though it is a bit risky .

The reason .. cam covers are matched to the cylinder heads .. whilst you could replace one there is a good chance it will be tight on the cam shafts.. a matched pair for this reason.

just to point out .. if you fit any kind of stainless steel bolt .. you Must grease it .. i learnt the hard way with exhaust flange bolts .. no grease and they just don't come undo again .. it's like the thread has stretched .. probably the plating has broken off causing this but either way .. it don't come undone in one piece .


Copper grease .. it was only since being here i've been told about galvanic corrosion ? copper grease being bad on ally stuff ?

At work we use ally grease and always have from OPC to the Indy i'm now at but this corrosion thing is not something i've ever seen ..

Not uncommon to see caliper bolts covered in it .. i've never seen an issue and indeed .. a grease of any kind is far better than none at all .. none means there's a good chance the bolt won't come out .


Anyways .. copper grease .. i don't use it .. i'm not interested in arguing about its properties .. but i've yet to see an issue from it being used .

One for the metallurgists to argue over i feel .



Short answer .. one bolt will retain a coil so leave it at that ..

 

[Damo996]

What a nightmare, I have a couple that a rounded off which I need to get out at some point to change the plugs.

 

[Pip1968]

I use this instead of copper slip. V high temperature anti seize paste.

https://tygrisindustrial.com/tygris...ygris-nickel-anti-seize-compound-tg8005-500g/

Mark

How does this differ from the Aluminium anti seize paste also on that website - aside from 760 C vs 1420 C ? Is it better for different metals?

Pip

 

[Kersidan]

I use this instead of copper slip. V high temperature anti seize paste.

https://tygrisindustrial.com/tygris...ygris-nickel-anti-seize-compound-tg8005-500g/

Mark

How does this differ from the Aluminium anti seize paste also on that website - aside from 760 C vs 1420 C ? Is it better for different metals?

Pip

I don't know, I went on a recommendation on a forum but also the higher temperature rating seemed in the right direction.

 

[deMort]

There is nothing wrong with using a high temp grease but this is a bit overkill for normal usage ..

Only the cat gets really hot and its operating temp under high load would be in the region of 5-600 degrees C.... it actually melts at around 1000 degrees which is less than this greases rating .

The closest bolts to that would be the flange ones and they would be a couple hundred degrees below that .

You have the tub though and it will last you for many years so that's fine but for anyone else .. i would tend to say .. get the cheaper option .. 760 is plenty enough for the temps reached on these cars .