Torque Wrench Buggered!

[SweetBadger 94]

Not having the best of days!!!

 

Firstly I think my master cylinder is fooked, went for a blast today and the pedal went really hard so I couldn't apply the brakes... Scary stuff... This only happens when I brake frequently or pump the pedal. Is there a one way valve that can be replaced or is it a replacement m/c jobbie?

 

Secondly, I got round to putting my re-ground MI crank in today and all was going well, crank spins smoothly, endfloat is 0.1 mm so I decided to torque up the mains properly with my newly bought draper torque wrench... Bad idea! Setting the wench to 54 nm, I started tightening, and the bolts kept turning looked and felt like I was never going to get the wrench to break away. So I set it to its lowest setting 30nm, to make sure it was working properly and it finally broke away on one ofthe main bolts, so assuming it was working properly I continued only to shear a bloody main bolt in the block . Surely this wouldn't happen at 30Nm!? Also it looks like I've stretched the thread on the 2 studs for the middle bearing cap - it goes slightly thinner in diameter where the top thread is!

 

So what do do now, thinking I should probably replace the main bolts now as a matter of course, so anyone have any prices on those, plus the 2 main studs?

 

Now that the rest of the bolt stuck in the block is not under tension what are my chances of getting it out with an easy out? Or should I just take it to a machinist?

 

Thanks,

Alex.

[Anthony 1,003]

Sounds more like a servo problem than a master cylinder one to me.

 

And yes, something definately sounds amiss with that torque wrench as 30Nm isn't very much at all - you should very easily be able to "click" that off without putting hard any effort in.

 

I think the snapped bolt should come out without too much grief since it snapped tightening it up. Drill a hole big enough to use the largest easy-out that you can (trying to keep the swarf from getting into the block) and take it slowly with the easy-out!

[SweetBadger 94]

Sounds more like a servo problem than a master cylinder one to me.

 

And yes, something definately sounds amiss with that torque wrench as 30Nm isn't very much at all - you should very easily be able to "click" that off without putting hard any effort in.

 

I think the snapped bolt should come out without too much grief since it snapped tightening it up. Drill a hole big enough to use the largest easy-out that you can (trying to keep the swarf from getting into the block) and take it slowly with the easy-out!

 

Ok thanks, Anthony, I'll give that a go. Is it possible to get the servo off without having to pull the master cylinder out, that way I wont have to bleed the brake system!

 

Hmm, I might have been a bit hard on the torque wrench, as I did hear a small click , but I was expecting something a bit more obvious, and the instruction manual did say that it would 'break away' which was what I was looking for. I'll give it a more through test tomorrow on something less expensive!

[Guest BrainFluid]

If you kept the receipt for the wrench I'ld go back to the shop and get as much as you can out of them.

 

When you go and pay good money for a torque wrench you would expect it to be 100% considering the whole point of buying one!

 

If you hav'nt got the recipt go and buy another one from the same shop and take the old one back with the new receipt (as long as the old one isnt too battered!).

 

Somthing like this just isnt on in my opinion.

 

Give um What For mrBadger!

[PumaRacing 2]

Ok thanks, Anthony, I'll give that a go. Is it possible to get the servo off without having to pull the master cylinder out, that way I wont have to bleed the brake system!

 

Hmm, I might have been a bit hard on the torque wrench, as I did hear a small click , but I was expecting something a bit more obvious, and the instruction manual did say that it would 'break away' which was what I was looking for. I'll give it a more through test tomorrow on something less expensive!

 

Plonker. That's all a click type torque wrench does do - give a small click. Then it goes past the click stop and you can lean on it as hard as you like. To continue to lean on it until mains bolts break means you don't have much in the way of mechanical sympathy though.

 

To remove the stretched centre studs just lock two nuts together on each stud and apply a spanner to the bottom one. Then fit new ones and new nuts. I routinely remove and refit them when I'm prepping race engines. They only want refitting at about 30 ft lbs - DON'T try and torque them up to the nut torque specification.

 

The broken bolt will just wind out by hand as it isn't under tension anymore.

[Daxed 7]

Be a good idea to have a play with the new wrench in a test situation to get used to the feel of it. Find a nice big, already tight bolt and just get used to what the click off point feels like. At low settings on wrenches that encompass a high range the click off can be fairly discreet and I would suspect that as Puma says you have possibly missed it.

 

Whilst practising get used to what each setting feels like in terms of just how hard you are pushing to get a torque of 20, 30, 40 ..etc N/m. This then gives you an expectation of when the wrench will click at any desired setting.

 

Other option to consider funds providing is to buy another torque wrench to add to what I assume is your ½ drive one. Get a 3/8 drive model with a much lower maximum say 50N/m and this will give a far more positive and noticeable click off at lower settings. Nice to have but not really necessary if you get used to the big wrench.

 

The brake problem sounds far more worrying. The brake pedal goes solid (as if the brakes were fully applied) but the brakes arent on, is that right? Anthony, what makes you think thats a servo problem? Bleeding the brakes sounds like its going to be a very minor inconvenience compared to sorting this.

[gti_al 1]

I had this happen with a new torque wrench minutes before i was going to attack the headbolts! I thought i would make sure it was working properly on a wheel nut, and even set at 10nm i couldn't make the thing click...

 

Maybe check it next to one that is known to work properly?

[SweetBadger 94]

Plonker. That's all a click type torque wrench does do - give a small click. Then it goes past the click stop and you can lean on it as hard as you like. To continue to lean on it until mains bolts break means you don't have much in the way of mechanical sympathy though.

 

Harsh but fair! Yep was totally my fault, going back to it now it's obvious where the click is , oh well no real harm done in the end, I got the bolt out using an easy out with no drama. As for not having much mechanical sympathy, although it was a daft thing to do, in my defence I've never worked with a 0.5m lever or with bolts of this size and so when comparing the relative force I was applying to the wrench with the force I normally have to apply with my quite small socket set, it seemed feasible at the time that I was applying the correct torque... Now I know how to use the wrench and have got a feel for it I won't be making that mistake again, and I'd advise anyone using a torqe wrench for the first time to hae a try on something un-important, as Daxed says get a feel for it before making a mess of things like I did!

 

The brake problem sounds far more worrying. The brake pedal goes solid (as if the brakes were fully applied) but the brakes arent on, is that right? Anthony, what makes you think thats a servo problem? Bleeding the brakes sounds like its going to be a very minor inconvenience compared to sorting this.

 

I think Anthony's probably right with the servo diagnosis, to clarify the pedal goes solid at the top of the stroke, just like when you pump the pedal when the engines not on and there's no vacuum assist. So it's fine for normal driving, but as soon as I start really using the brakes and pumping the pedal more the problem shows itself. Obviously I won't be doing much driving untill I sort this, but is there any way of disabling the servo altogether, untill I can get a suitable replacement, or find the cause of the problem?

[jackherer 543]

but is there any way of disabling the servo altogether, untill I can get a suitable replacement, or find the cause of the problem?

 

just disconnect the air hose to the inlet and block the inlet so there are no leaks.

[pugrallye 0]

its not a cheapo torque wrench is it? they are known to be dodgy anyway, if youe using a 1/2" drive wrench to do big end bolts, chances are even if the scale says 30nm it wont really register that low, use small wrench for small jobs!

If you pull off the cap itself, shouldnt really need easyouts to get snapped bolt out, as they normally shear at head, so should be relatively loose in there

Edited February 12, 2006 by pugrallye

[SweetBadger 94]

its not a cheapo torque wrench is it? they are known to be dodgy anyway, if youe using a 1/2" drive wrench to do big end bolts, chances are even if the scale says 30nm it wont really register that low, use small wrench for small jobs!

If you pull off the cap itself, shouldnt really need easyouts to get snapped bolt out, as they normally shear at head, so should be relatively loose in there

 

It's a fairly cheap draper wrench, but was reviewed (some magazine artical I found on the web) and tested to be accurate, best value etc... Wish it had sheared off at the head, it sheared just above where the thread started so I had to whip the crank, shells etc... out and use an easy out. The crank's back in now and I'll go order the bolts and studs from pug, I think pug is the only place you can get them from, probably take a week or so to get them, right pain in the arse!

 

A handy tip for anyone who finds themselves having to do something like this is to keep a strong magnet handy to trap the swarf as it comes off the drill, makes for a lot less cleaning after!