Rounded off bolt.

Hello All;

Just been doing the back brakes on my golf convertible, one side went really well, no problems. Just gone to do the other side, and managed to round off one of the bolts holding the wheel cylinder to the back plate.       I even had a really good fitting 5mm hex bit, but it still managed to round off. I think the metal was a little too rusty.  

So any ideas on best way of getting it out before I go and attempt it tomorrow?? Access is very resteicted, so I can't drill it out very easily, so I'm hoping for another suggestion if anyone's got any?  

Cheers

Mike.

It likely that the bolt has collected mud and crap inside the recess where the socket goes so get a small screwdriver and see if you can dig it out then gently tap the hex socket in with a hammer and give that a try, if that doesnt work try a hammer and chisel

I've managed to shift rounded off bolts with mole grips before. You need to clean off the bolt head and surrounding area well (wire brush on a drill), use loads of penetrating fluid (Plus Gas, or whatever), and really SQUEEZE the grips onto the bolt. If that doesn't work then you can get sockets that grip the flats of the bolt rather than the edges. I've also welded a nut to the top of a rounded bolt before after grinding the head back to clean metal. The combination of heat plus fresh (non-rounded) edges usually means a socket will undo it. However, given brake fluid is mega-inflammable, I wouldn't advise it in this case (!). Another option is cutting the head off the bolt with a junior hacksaw / hacksaw blade. If all else fails why not take the backplate off with cylinder still attached - then you can really give it some stick !
Good luck with it,
Mark

Hi there,

You could try instead of a hex socket, a spline socket of equivalent size, maybe slightly bigger. When you have one, try and tap/knock it in to the hex recess. I have had sucess with this method in the past after taking the edges off a hex hole.
Spline fittings are double hex fittings and quite often used on moderncars. In fact they are used to hold the front drive shaft flanges on the mk1/2 etc.
dont forget WD40 though or maybe a little heat from a blow torch to help free things off.

Hope this helps.

I used a spline tool on a rounded hex and it worked perfectly and the spline tool is normally still usable after doing this

I had exactly the same problem on my brother's Polo, I needed to replace the wheel cylinder because the bleed nipple sheared off when I was bleeding the brakes.

I took the drum off and drilled the hex bolts out from that side, it butchered all the threads on the wheel cylinder also but as I was changing it anyway it didn't matter. Just make sure you dont drill the back plate!

This is the easiest method of removal if the hex bold head is really knackered. The metal of the wheel cylinder is relatively soft so drills quite easily.

Cheers,

Ross

did it in the end by removing the backplate and drilled the head off the bolt. I didn't realise how easily it came off, only 4 bolts holding it and the rear axle on, they don't even look that strong considoring the whole of the weight of the car is on them!!