Rescuing threads

[KennyN]

When you clear out any damaged / crossed thread with a tap you will be removing metal that had to come from somewhere , that somewhere is from the existing thread therefore weakening it , especially important if it needs to be tightened to 115nm.

How thick is the threaded part (ie how many threads) ?

K

 

[ChrisEdu]

When you clear out any damaged / crossed thread with a tap you will be removing metal that had to come from somewhere , that somewhere is from the existing thread therefore weakening it , especially important if it needs to be tightened to 115nm.

How thick is the threaded part (ie how many threads) ?

K

Not sure how many, but 35mm long and a 1.5mm pitch.

 

[KennyN]

Not sure how many, but 35mm long and a 1.5mm pitch.

Not the actual bolt , the part it screws into ?

K

PS - Is this the front or rear we are working on , as you mentioned caliper carrier but if it is the rear the caliper bolts straight onto the hub - AFAIK

 

[ChrisEdu]

Not the actual bolt , the part it screws into ?

K

PS - Is this the front or rear we are working on , as you mentioned caliper carrier but if it is the rear the caliper bolts straight onto the hub - AFAIK

It's the rear OS. From what I have read, it bolts onto a knuckle?

 

[KennyN]

Is it one of the holes (with the bolts) that is causing the problems (pic 3)?

If so , they look like part of the rear hub.

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If you are clearing out the hole with a tap from the rear just make sure it goes in nice and straight as you dont want to worsen the issue. If the hub needs to come off to repair the thread then i would just get a used hub and fit that instead then you know the caliper fitment is "factory".

K

 

[Will]

I fear the OP would struggle with replacing the whole hub though? Might be time to call in some help if the threads have had it

 

[ChrisEdu]

Is it one of the holes (with the bolts) that is causing the problems (pic 3)?

If so , they look like part of the rear hub.

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If you are clearing out the hole with a tap from the rear just make sure it goes in nice and straight as you dont want to worsen the issue. If the hub needs to come off to repair the thread then i would just get a used hub and fit that instead then you know the caliper fitment is "factory".

K

Yeah, that's it, and pic 3 shows the bolts.
I had considered getting the part, but it looks a bit awkward to change.

 

[AW8]

I have done fluids & pads before, however, anything with significant mileage or years under the belt can bite back.....especially for me & when considering my limited ability & tools.

I will put my hands up to shying away from anything that might involve siezed sheared or failed nuts/bolts & fastenings.

Respect for OP for having a go.

Good luck

 

[KennyN]

Yeah, that's it, and pic 3 shows the bolts.
I had considered getting the part, but it looks a bit awkward to change.

It also looks expensive , if you are purchasing new.

First things first , clear out your hole and try and refit the caliper with the new bolts - if the torque wrench clicks at 115nm then you have had a result , if the thread strips then you can take it from there.

Try and use a proper wrench when using your tap as it will be easier to keep it "square" , also use some form of cutting compound if you can. Where in the UK are you as there maybe someone close who can assist with tools / materials / advice etc.

Even using a thread repair kit properly may involve removing the hub , if that is the case then i would just get a used hub from eBay and fit that along with a new bearing as a preventative measure.

K

 

[ChrisEdu]

It also looks expensive , if you are purchasing new.

First things first , clear out your hole and try and refit the caliper with the new bolts - if the torque wrench clicks at 115nm then you have had a result , if the thread strips then you can take it from there.

Try and use a proper wrench when using your tap as it will be easier to keep it "square" , also use some form of cutting compound if you can. Where in the UK are you as there maybe someone close who can assist with tools / materials / advice etc.

Even using a thread repair kit properly may involve removing the hub , if that is the case then i would just get a used hub from eBay and fit that along with a new bearing as a preventative measure.

K

I'm in West Sussex, down by the sea.

 

[a111r]

I'd use one of the old bolts as a tap to clean up the thread first, after dremmelling two equi-spaced thin slots down it, to accommodate the removed debris. I'd also use a light oil with it.
This method won't cause any damage, which tapping might, if you're new to it.

Edit: I've just seen that you mentioned this in the OP.

 

[ChrisEdu]

I'd use one of the old bolts as a tap to clean up the thread first, after dremmelling two equi-spaced thin slots down it, to accommodate the removed debris. I'd also use a light oil with it.
This method won't cause any damage, which tapping might, if you're new to it.

Edit: I've just seen that you mentioned this in the OP.

Yeah, 'twas in a YouTube video with a Merc dude.

 

[ChrisEdu]

Hoping to have another go at this either Friday, or the weekend. If things don't go well, and it becomes a case of needing to replace the hub unit, or wave some other magic wand, does anybody know of a reliable mobile mechanic that would cover my area? I say mobile, as I'm thinking the car won't be safe to drive on just three brakes!?

 

[AW8]

Tou say your area is "West Sussex down by the Sea".......I am sure that you know his covers approx 50 miles of coastline (from Emsworth to Shoreham).... Mechanics anywhere from Portsmouth to Brighton might be suitable depending on where you are.

Some may travel from fixed garage workshops to assist..........at a price. Sadly some mechanics are reluctant to assist folk who d.i.y. & come unstuck

I don't know any "mobile mechanics" but a better rough idea of location & acceptable hourly rate may be useful.

 

[ChrisEdu]

Tou say your area is "West Sussex down by the Sea".......I am sure that you know his covers approx 50 miles of coastline (from Emsworth to Shoreham).... Mechanics anywhere from Portsmouth to Brighton might be suitable depending on where you are.

Some may travel from fixed garage workshops to assist..........at a price. Sadly some mechanics are reluctant to assist folk who d.i.y. & come unstuck

I don't know any "mobile mechanics" but a better rough idea of location & acceptable hourly rate may be useful.

Just outside Worthing.

 

[AW8]

Just outside Worthing.

Maybe someone on her can make a recommendation.

I will private message you also.

 

[ChrisEdu]

I know a mechanic in West Worthing who has done "friends and family" work me in the past....He doesn't do mobile work. No idea if he is skilled in thread rescue work.

If to the east of Worthing AJ Roberston in Hove has done work on cars for me before. Alan used to run the business...Proper old school mechanic & honest. He tends to do a lot of work on analogue Mercs & BMW's... I cant speak for him but I suspect he would likely want car taken/conveyed to his workshop.

I have spoken to Dave at R&G Lancing before re a gearbox flush on a Range Rover.....he seemed a decent honest chap & was linked to someone on a range rover forum iirc.

If you are west of Worthing Terry at Spencer St Garage Bognor is a genuinely skilled guy...prior taught by his father who used to rebuild tractor engines & do complex engine rebuild work.

Over the years I have only given repeat business to decent honest & honest folk. Sure some of them are characters, but I prefer competent characters over BS or smoked glass & mirrors.

Al folk I have mentioned are decent but likely to be quite direct if messed about or haggled with on 1st outing. If they cant help they may be able to signpost you.

HTH

Thanks for that. I have the number for the guy the garage are using to sort sheared bolts on my wife's car, so will see what he says. If he can't help, I'll look into your suggestions.

 

[ChrisEdu]

I have an engineer coming on Friday to rectify the bolt holes. He is used by the local garage, so has plenty of experience. Rather than using helicoils, he uses a tubular insert that becomes permanently secured to the part being repaired, rather than potentially coming out like a helicoil. So, hopefully, I should have the W211 back in action by Saturday.
His estimate, for the two holes is circa £100, so not a cheap fix, but on balance easier, and likely cheaper, than replacing the knuckle, which would involve taking everything apart.

 

[AW8]

If it makes you feel any better....it is not un-common for some garages/mechanics to out source such remedial work to someone experienced at doing this.

 

[ChrisEdu]

If it makes you feel any better....it is not un-common for some garages/mechanics to out source such remedial work to someone experienced at doing this.

I actually feel better knowing an engineer, used to working to tight tolerances will be doing it, rather than somebody that thinks it's good enough at half a mm.