Serious problem with dogbone mount...

[greesha]

Ok a photo first.

OK as you can clearly see my THS dogbone has snapped. Middle bolt is missing. I have undone all the bolts. Thread is gone in the hole that has missing bolt. I have seriously no idea what to do now... I have heard something about helicoil but i have absolutely no idea how to do that and which one to use :/


What type/size bolt should be used for that? Maybe there is still some thread left on top if i use slightly longer bolt?

Please need advice. Thanks

 

[Ronin225]

Bolt will probably be M10 or M12
Helicoil kits allow you to drill out knackered hole ( as long as sufficient material ) larger then tap new hole larger and insert helicoil. This looks a bit like a spring, the outer thread grips on the new thread you tap and the bolts thread matches the internal one
However due to the strains on these mounts i wouldnt recommend it
How bad is the thread? no way of retapping and getting a new bolt?
You did use loctite on the bolt when installed?

 

[greesha]

No i haven't used loctite when i was installing that one. I did use all to correct torque on the bolts.

I guess its time for a WALK to screwfix to find a new bolt.

Ronin im sorry but don't understand what do you mean by "retapping". Could you make it a bit simplier for me please?

Thanks for advice

 

[Ronin225]

If the thread is not too damaged you can run the tap ( this cuts the thread) back down the hole, this cleans the threads and forms the back into proper pitch, etc.
However if the threads are completely stripped there will not be enough material to allow torqueing up
If you do get a bolt from DIY place only use it temporarily, the bolts you need are stretch bolts, so upto torque then 1/4 of a turn more
Some loctite or thread lock would have probably stopped the bolt working loose and damaging threads whilst coming out

 

[foxes]

Is it a 'Tap' key that he requires?

 

[greesha]

Im just going to visit my mechanic tomorrow. But i guess i cant really drive a car without a dogbone ... :/

 

[ashley600]

I thought helicoil was meant to be stronger than the original thread. I ripped out the threads on the engine mounts on my trackbike Fitting crash mushrooms and got a much firmer fixing after the heilcoil.

 

[dholdi]

Imho a helicoil would be ok in this application.
The forces on the bolt are at 90 degrees to the axis of the bolt so they arnt trying to pull the bolt out of its fixing.
Pity you dont live a bit nearer, Ive got a load of helicoil kits in my garage from when I used to work for a proper engineering company ( sadly hardly any left nowadays )

 

[Ronin225]

The choice to not use a helicoil is a personal one, i dont think they are that good and not had the best experiences using them
But i do use them at work as a last resort, in one of the few engineering companies left, tis true an industry hard hit in the uk

 

[dholdi]

Yep, know what you mean, they are a last resort repair solution but in my experience they have been fine. I dont think I would like to use them on a critical component where the forces act in line with the axis of the bolt and would be trying to pull the bolt directly out of the thread. In this case though he doesnt really have any viable alternatives, mig/ tig welding, redrilling and tapping to the original size would be pretty tricky in situ. Tapping out to the next size up would mean the bolt wouldnt go through the mount. If theres enough meat around the hole then an insert with the correct id thread could be made but again this would be tricky in situ.
Who do you work for down there ? My sister lives in that area. I served my time with English Electric / GEC here in Preston, home of the Lightning / Canbera / Eurostar - now a retail park and warehouse

 

[ibizacupra]

get it helicoiled-simples

 

[andycupra]

how strong and reliable are helicoils.. someone had there sump plug helicoiled on another thread, seems this failed.. and apparently the garage said it might not work.

Surely if dont properly its pretty strong?

 

[LEE69]

You can heli-coil caliper brackets when they get stripped.

 

[greesha]

OK i found a local mobile helicoiler. Will give him a ring tomorrow.

Anyone can give some idea of a price tag for this service?

 

[dholdi]

Well in an ideal location it shouldnt take long, redrill hole to helicoil tapping size, cut new thread with helicoil tap, insert insert, rebolt up your bracket. However I guess he will be working on your drive under the car on axle stands and he will have to come out to you in his van. I would guess at £60-120.
Personally, I would do it for mates for nowt and anyone else a few beer tokens, but I'm not making my living doing it.

 

[greesha]

Guys i know that the bolt is M10X70mm but what is the thread size? 1.0 1.25 1.5 ? How to check that if i have that bolt that needs to fit into that?

Sorry for daft questions guys.

I dont know which helicoil repair set to buy.

Helicoil would have to be about 35 - 40mm as that much goes inside the engine block (but i have to check that properly)

Or maybe somebody knows some cheap helicoil mobile service around Slough ?

Thanks

first quote: 100 pounds, and the car has to be at some garage as they dont it for private customers :/

 

[andycupra]

The cost involved in getting it helicoiled seems pricey enough that getting a new mount is just as cost effective?
saying that i dont know how much the dogbone mount is..

*** edit***
so they are £50-60???
so surely a replacement is the way to go?

 

[greesha]

Yes Andy mount is not a problem. Problem is that you have to use a 70mm bolt which goes though the mount and then inside the engine block. And there is no thread now in that hole in engine block so i just cant screw it in. I need to make a new thread inside the engine block.

helicoil repair kit M10X1.5 (which i suspect it is) costs 20 pounds on ebay.

EDIT: Btw i found the way how to measure the thread size. I can check it when i will be home

 

[andycupra]

aha, silly me i didnt appreciate the thread was on the engine block, (wouldnt take much thought to realise this)
helicoil would appear the way to go.

 

[Redrat]

Heli-coil

Hi Greesha,
Make sure that the thread insert kit ( heli-coil is a brand name) comes complete with a tap. You will also need a tap - wrench to hold the tap in to do the job correctly, also use some cutting/ thread compound, grease will do as a last resort. Be very careful when "tapping" the new thread, make sure that the tap is square (straight) when starting to tap the hole. once started, for every two turns of the tap in, make 1/2 turn out (backwards) to help break the swarf and ease the tapping. Once done completely clean the new threads before attempting to fit the thread-insert. Be very careful when fitting the insert, wind it in slowly as doing it too fast can sometimes result in the insert jumping a thread ( which means that You need to pull it out with a pair of pliers, then try again with a new insert. Take Your time & all should go OK, Hope this helps Good Luck.

PS: Thread-inserts are not always a last resort, they are used commonly in Alloy components where strength & High torques are required, I use them regularly in My Job, if fitted correctly they are far stronger than threading straight into alloy.