M42 valve cover bolt hole ruined

[MrriS]

I overtightened one of the valve cover bolts on my 318iS's M42 .. My good friend was convinced he was able to fix it .. turns out what he did without me there didn't fix it, but made it worse.

A 7mm drill might clean away enough; 7,5mm will clear away the damaged thread and 8mm will just drill a brand new smooth hole. But if you go out and buy a helicoil set to end up with the correct M6x1 thread, you get a 6,3mm drill with it. I can tell you that a 6,3mm hole wont hit anything let alone the messed up threads..

Soooo, how do i go from a 7,5mm (or 8mm) hole back to M6x1 ?

Any suggestions?

[flybynite]

Try looking for 'Wurth Timesert' you might need the oversize 'big sert'

However as it is only a valve cover, my first port of call would be to thoroughly clean it with brake cleaner let it dry, warm it up with a heat gun/hair dryer and then fill it with some (well mixed) epoxy metal repair. Let it properly cure, drill and tap a new 6mm hole.

Buy a small torque wrench.

If that fails then drill out and timesert/bigsert, nothing lost.

[martauto]

Try looking for 'Wurth Timesert' you might need the oversize 'big sert'

However as it is only a valve cover, my first port of call would be to thoroughly clean it with brake cleaner let it dry, warm it up with a heat gun/hair dryer and then fill it with some (well mixed) epoxy metal repair. Let it properly cure, drill and tap a new 6mm hole.

Buy a small torque wrench.

If that fails then drill out and timesert/bigsert, nothing lost.

What this guy say`s and you can also drill out for a 10mm bolt and saw a bit off and locktight it in place .
Drill and tap for M6
Best if you can use an ally bolt , it makes things a bit easier.

Mart.

[MrriS]

Thanks a million, great advice! I'm still trying (as would anybody i guess?) to find the least invasive solution.. I'll look into the Wurth Helicoils first!

[flybynite]

Thanks a million, great advice! I'm still trying (as would anybody i guess?) to find the least invasive solution.. I'll look into the Wurth Helicoils first!

Just be careful, Time-serts are different to helicoils, one is solid one is a coil. If you ask for a Wurth helicoil you will get confused looks.

Least invasive would be epoxy, drilled and tapped is plenty strong enough for the cam cover.

Or as mart says above make your own insert using end of a bolt, On a cam cover it will work fine. If you are careful and centre the 6mm bit well (go 3,4,5 mm holes first) you may be able to get away with an 8mm alloy bolt. As above use some good threadlock on the 8mm thread to stop it winding out.

[MrriS]

https://www.fittings.space/gtm26-m10x15m-m6x10f there are these aswell, but like you guys (thanks again) also indicate .. making an M10 hole there is last measure

Anyone has a link to a descent brand metal epoxy? Must say it sounds the least invasive solution

[MrriS]

hold up, look what a buddy of mine draged out of the old interweb: https://www.tools2go.nl/Schroefdraad-re ... -x-1-5-dlg

Would you guys use some sort of threadlock? Loctite or something similar? I'm afraid most of those products aren't heat resistant..

might be wort a shot trying this first

[martauto]

Least invasive would be epoxy, drilled and tapped is plenty strong enough for the cam cover.

This sounds the best way to go , like said above, "Plenty strong enough" and very easy to put back if no good too

Mart.

[MrriS]

Just a litlle scared of drilling straight.. I ordered these: https://www.tools2go-uk.com/Threaded-In ... pcs?Lng=en and am hoping that with enough serious loctite (red label?) I can fix things without a drill..

[onthames]

Just a litlle scared of drilling straight.. I ordered these: https://www.tools2go-uk.com/Threaded-In ... pcs?Lng=en and am hoping that with enough serious loctite (red label?) I can fix things without a drill..

You'll be fine. I'd be more worried about getting metal shavings anywhere. I'd stick a vacuum hose next to it when you're drilling and use rags + masking tape everywhere and blow off before removing. I recently used a clark helicoil kit from machine mart on a stripped thread on the timing belt cover. It came with all the tools required but you'll need a holder for the tap: https://www.machinemart.co.uk/c/thread-repair-tools/

[flybynite]

I recently used a clark helicoil kit from machine mart on a stripped thread on the timing belt cover. It came with all the tools required but you'll need a holder for the tap: https://www.machinemart.co.uk/c/thread-repair-tools/

Problem is here the hole is already too big for the Helicoil, you can get big helicoils but the solid time-sert type are far better when oversize.

The inserts the OP listed above will work but it will need some high temperature thread lock as they don't swage the insert like the time-sert type thread repairs.

[onthames]

I recently used a clark helicoil kit from machine mart on a stripped thread on the timing belt cover. It came with all the tools required but you'll need a holder for the tap: https://www.machinemart.co.uk/c/thread-repair-tools/

Problem is here the hole is already too big for the Helicoil, you can get big helicoils but the solid time-sert type are far better when oversize.

The inserts the OP listed above will work but it will need some high temperature thread lock as they don't swage the insert like the time-sert type thread repairs.

Ah fair enough.
Just wondering is it possible to just fill the hole with weld and then just retap a hole of the correct size?

[flybynite]

Ah fair enough.
Just wondering is it possible to just fill the hole with weld and then just retap a hole of the correct size?

Possible but you would need someone handy with a TIG and you would need to match the alloy carefully as you will give yourself more trouble if you get it wrong. Guys who do head welding would know but getting an arc down the bottom of a hole isn't the easiest thing to do.

Personally if it is something that needs holding well then I time-sert. If not then I score or tap a light thread to give a key and then epoxy. Nothing fancy just Araldite Metal and get conditions as close to ideal as possible. If it does fail then I drill out again and time-sert.

[MrriS]

The inserts the OP listed above will work but it will need some high temperature thread lock as they don't swage the insert like the time-sert type thread repairs.

Hoping so, i've ordered Loctite 272 (normal loctite is up to 150degrees celsius, and 272 is the high temperature variant). If that fails I will indeed get the metal epoxy and drill as those selftapping wurth inserts aren't that easy available here to my knowledge/findings..

Again, thanks for all the advice guys!!!

[rix313]

Ah fair enough.
Just wondering is it possible to just fill the hole with weld and then just retap a hole of the correct size?

No need to over complicate things.


That does look pretty routed, sometimes mates dhould be mates and leave things alone! With a helicoil you just need to check you have enough material there to be able to tap the hole out to the next size up for the helicoil. It looks like you should do. The next best thing, as suggested by mart is a time-sert which are much more robust and there are different versions (standard and heavy duty) if the hole ends up being too big for a standard one. They also have lockig tabs so it'll never spin out of place. People always do these bolts up too tight sadly. If you have it, I do have a how to on my instagram story highlights for a helicoil repair I did on one of these engines.

[MrriS]

Ah fair enough.
Just wondering is it possible to just fill the hole with weld and then just retap a hole of the correct size?

No need to over complicate things.


That does look pretty routed, sometimes mates dhould be mates and leave things alone! With a helicoil you just need to check you have enough material there to be able to tap the hole out to the next size up for the helicoil. It looks like you should do. The next best thing, as suggested by mart is a time-sert which are much more robust and there are different versions (standard and heavy duty) if the hole ends up being too big for a standard one. They also have lockig tabs so it'll never spin out of place. People always do these bolts up too tight sadly. If you have it, I do have a how to on my instagram story highlights for a helicoil repair I did on one of these engines.

Shoot me a link? always interested!

As it sits now i only just had the time to check of the inserts i bought are big enough ( https://www.tools2go.nl/Schroefdraad-re ... -x-1-5-dlg ) and they are bigger than the molested hole so with the brand new wire taps and some red loctite (couldn't get the 272 sadly wich is more heat resistant) I think it'll work..

Still not shure if i'll remove the intake manifold cause it's sitting in the way of a wire tap tool spinning freely.. sounds like the smart way

Things move slowly, lot's of stuff to do on the only evening (tuesday) i can actually go to my car and work on it.. like today i have a brake job on the daily

[rix313]

The trick I did was use a 1/4 long extension on the back of the tap and you can then turn the handle freely. That or look at at ratchet handle.

https://www.instagram.com/s/aGlnaGxpZ2h ... hare_sheet

[martauto]

The trick I did was use a 1/4 long extension on the back of the tap and you can then turn the handle freely. That or look at at ratchet handle.

https://www.instagram.com/s/aGlnaGxpZ2h ... hare_sheet

Did you break the tag at the bottom of the coil or was there enough thread in the new coil ?

Mart.

[rix313]

Didn't need to in this instance to be honest. The standard bolts have a very short thread on them.