Rescuing threads

[ChrisEdu]

Thought I'd start a separate thread for this query, as it is almost certainly not purely applicable to my current issue.

As some of you might know, I have been having a bit of a mare trying to do my O/S brake. First it was a pig to remove, then I needed a new caliper carrier, and now to the latest issue.

When I was removing it, I noticed that the bolts seemed much more difficult to remove than on any of the other brakes. However, I persevered and, with some patience, got them out. Then, eventually, I was in a positio0n to refit the caliper. This is where the latest pro0blem has now struck.

The top caliper bolt is extremely stiff when trying to get it back in. The bottom one went in relatively easily, but didn't want to torque fully to the prescribed 115Nm. Today, I collected some new bolts from the MB dealership to have another try. The only thing is, I'm rather concerned that maybe there's an issue with the thread on the inside? If so, what would be the best course of action?

I believe the bolts used for the fixing are M12 x 1.5 x 35mm, going by the new ones. One video I saw suggested putting some slots into an old bolt and using it to try to clean the internal thread. Is this sensible? Would getting a suitable tap and tie be the way to go, re-cutting the internal thread?

What do the collective sages of the forum think?

 

[Y3CHR]

Hi Chris,

You could try tapping out the thread, another option if that fails is to fit Helicoils.

 

[ChrisEdu]

Hi Chris,

You could try tapping out the thread, another option if that fails is to fit Helicoils.

Would helicoils be safe / recommended on brake calipers?

 

[Y3CHR]

Would helicoils be safe / recommended on brake calipers?

Perfectly safe buddy, you get different rated helicoils depending on the application.

 

[KennyN]

Normally if a thread has been crossed / damaged then tapping it out will only weaken whatever thread is remaining meaning you will struggle to achieve the correct torque without stripping it completely.

I dont fancy helicoils on any part of the braking system , depending on how many threads are present.

If it is M12 x 1.5 then that is metric fine so a tap may not be readily available from the usual outlets.

Excuse my ignorance , is it the thread on the caliper or thread on the carrier ?

K

 

[ivan1983]

I ended up tapping the threads on the brake callipers on my w140.

I think a combination of age, corrosion, torque and heat warpes the threads somewhat.

As your just refreshing an existing thread it will require very little effort as long as its well lubricated

 

[ChrisEdu]

I ended up tapping the threads on the brake callipers on my w140.

I think a combination of age, corrosion, torque and heat warpes the threads somewhat.

As your just refreshing an existing thread it will require very little effort as long as its well lubricated

I guess I could try this, then if it bu££ers it up even more, try the helicoils.

 

[pmcgsmurf]

They are usually 1.5 threads.
I'd get a tap and clean them with this.

A mate recently had exactly the same problem you are having, when we took the carrier to the workshop to do the threads it took ages to get them clean and the stuff coming out was black and horrible. I reckon it was something used at the factory from new.

 

[ivan1983]

They are usually 1.5 threads.
I'd get a tap and clean them with this.

A mate recently had exactly the same problem you are having, when we took the carrier to the workshop to do the threads it took ages to get them clean and the stuff coming out was black and horrible. I reckon it was something used at the factory from new.

Thread lock that has gone through a lot of heat cycles?

 

[pmcgsmurf]

Thread lock that has gone through a lot of heat cycles?

Possibly.

 

[clk320x]

This thread reminds me why I don’t DIY
Best of luck Chris hope you sort it soon

 

[ChrisEdu]

This thread reminds me why I don’t DIY
Best of luck Chris hope you sort it soon

Reminds me why I wish I was healthy enough to work, so I could pay somebody else to do it.
Added to that, I have been in so much pain lately, which this isn't helping. Woke last night in agony from my left arm.

 

[clk320x]

Reminds me why I wish I was healthy enough to work, so I could pay somebody else to do it.
Added to that, I have been in so much pain lately, which this isn't helping. Woke last night in agony from my left arm.

I meant no disrespect Chris, just some lighthearted banter. I’ve no idea of your personal situation. Hope things get better for you soon pal.

 

[ChrisEdu]

I meant no disrespect Chris, just some lighthearted banter. I’ve no idea of your personal situation. Hope things get better for you soon pal.

None taken, I was just saying.

Anyhow, just ordered a set of three taps and a die M12 x 1.5, so I'll wait for them to arrive before I go trying to put the bolts in, as I don't really want to ruin the new bolts from the outset.

 

[MrGreedy]

I agree with all the comments about giving this a go with a tap to chase the thread out. I've done this loads of times on various bolt holes. You'll easily know if the thread is naff in my experience as the tap and new bolt will obviously move in the thread, whereas the tap especially should be secure. Also, you shouldn't be removing much/virtually no metal when you chase the thread out. If it's cutting metal out, it's a sign something has been damaged.

 

[AMGeed]

46 minutes too late
I have an M12 1.5mm tap I could have posted to you.
I used it once to tap a stripped M12 wheel bolt thread on my first W210 .

If you still need it, PM me or post here.

 

[ChrisEdu]

46 minutes too late
I have an M12 1.5mm tap I could have posted to you.
I used it once to tap a stripped M12 wheel bolt thread on my first W210 .

If you still need it, PM me or post here.

D'oh! Thanks for the offer anyway.
The way things are going, it's going to be a race between getting my car finished vs my wife getting her back from the local garage, hopefully with the dpf issue fixed.
It comes to something when the only working car in the household is your teenager's 17yr old Focus!

 

[AMGeed]

^ You'll get there Chris. These snags are meant to try us.

 

[Will]

You can get special taps for cleaning threads out, rather than the type used for cutting new threads into drilled holes.

I’ve got a set similar to this:

Craftsman 40 Pc. Tap and Die Set Master Rethreader Part # 52105 Made USA for sale online | eBay

Find many great new & used options and get the best deals for Craftsman 40 Pc. Tap and Die Set Master Rethreader Part # 52105 Made USA at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

Ideal for cleaning out old thread lock, grease, light corrosion etc.

Have to say though, depending on how bad the thread is damaged you may well be better off with a helicoil (or time sert) etc. Unless it’s just old threadlock or similar you’ll just be tapping into damaged metal and it will be unlikely to give you a secure fit for the new bolt. Is this thread into alloy or steel?

 

[Will]

Just read the first post again:

The bottom one went in relatively easily, but didn't want to torque fully to the prescribed 115Nm.

Sounds too late for re-tapping I’m afraid. You’d be better off replacing the hub or getting someone to help you if you’re not experienced with drilling and tapping and inserting helicoils etc. You really need some kind of jig to centre the drill bit and get the new thread straight, otherwise the caliper will never bolt up properly.