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Just changed a brake hose on my mk2 golf. I've come to bleed the system but can't open the bleed valve as the nut is rusted. I've tried some penetrating fluid but it does not budge. The nut is begining to become rounded so that a spanner will soon have no grip on it. If I can't open the nut what are my options? Will I have to change the caliper?
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try a bit of carefully applied heat
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Sarb11,
I had one shear off on my Pug 405 some years back. As well as many that have been stubborn. Corrosion can weaken them considerably (and invisibly) so -do not force-!!
Use a decent penetrating fluid like "Plus Gas". Don't use graphite-based stuff if ABS sensors are nearby. Leave it for a few hours (at least). I have heard that a few taps with a small hammer (downwards) on the end of the nipple (akin to tapping a pin into a piece of delicate woodwork) can help. But be errm "gentle"
My other somewhat controversial advice would be to gently heat the surrounding caliper. No, not so it glows red... even gentle heat can free things up in a remarkable way. Some may disagree arguing that this could result in damage to seals (unlikely if gentle heat is used) and bubbles in the brake fluid (not an issue if you are bleeding).
If it is stubborn and will not move at all or shears off, I seem to recall that I drilled the old one out of my Pug (with lots of care)and unscrewed any remains.
Good luck
rg
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If all else fails, there is a heath robinson way around this. I had to resort to this mothod after once crashing a motorbike and sheering off the bleed nipple.
Push the piston out a short distance with some compressed air squirted down the brake pipe coupling. Pour in a quantity of brake fluid and slowly push the piston back until the fluid appears at the hole (imagine you're removing the air from a syringe). Reconnect the brake pipe. Jam a piece of wood between brake pad and brake disc to prevent the piston from moving. Get trusty assistant ready at the brake pedal and bleed the brake caliper by slackening off the brake hose. ie, treat the brake hose coupling as you would use the bleed nipple.
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The techniques above are relevant, but you are likely to need a new caliper. Try motor factors etc before VW though
You can also try taking the caliper off and ejecting the pistons by pressing the pedal before disconnecting the flexible, then taking out (with incredible care)the seals, before taking the caliper down to your local garage to get the nipple red hot with oxyacetylyene, then allowing to cool before trying plusgas, and then getting it red hot again. The advantage with oxyacetylene is that the nipple gets red hot quickly, without heating the aluminium caliper, so that differential expansion can do its best.
eventually, you will probably shear the nipple though. Most are overtightened, and the steel nipple and aluminium caliper are almost impossible to separate.
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DD's tip is the one I always used for years. Works a treat.
Now, I've come across something as good.
You can now buy a banjo fitting that plumbs straight into the feed pipe, and has a nipple on it.
You undo the feed pipe and screw it into the banjo bolt. Then screw the banjo into the caliper. Does exactly the same job as DD's method. Bleeds from above the caliper and below the hose feed.
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excellent idea Sean. Where can I get one of these valves from and how much does it cost? I presume the "banjo fitting" reamains attatched after fitting.
nice one cheers!
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They are made by Goodridge, and probably others, too.
I suggest you try all the usual large motor accessory places as this is a bit more specialised than GSF or Euro Car Parts (maybe not).
Considering that a caliper's £100 to £200 I suppose the banjo bolts are cheap at a fiver. VERY dear for a bolt, though IMHO.
Yes, it stays on forever more.
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Hi,
If you can slacken off the feed pipe going into the caliper, do so and you may be lucky yo expel the air. This is a two person job -whilst the pedal is being depressed you should be able to see the bubbles coming out until clear fluid starts to seep out. Tighten the feed pipe up and hopefully the pressure will be ok. If it is'nt, again undo the feed pipe and gently push the brake pads back, this will have the same effect of expelling the air. whilst doing this and the fluid runs clear, tighten pipe. I've done this before out of desperation and it worked. Failing that a last resort would be to strike the end of the bleed screw a few times not too hard. This may jar it enough for you to free it.
Good luck
--
These are the views of Robin the Technician with 35 years in the trade. I fix, therefore I am...
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As in other replies, try a little gentle heat on the top of the bleed valve or try gently tapping the bleed valve with a small hammer to try to break any corrosion hold. A pair of mole grips whilst trying either of these procedures is a good idea.
pastyman.
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A new caliper from, say, GSF isn't going to be more than about £70, I'm sure.
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Apologies, only just read this one!
Had the same problem a few years ago. Got the old bleed nipple out of the caliper by firstly soaking it in Plus Gas. Then I screwed in a suitably sized Ezi Out stud extractordown the centre. Finally I turned both the nipple with some Mole grips and the stud extractor together and the nipple unscrewed.
HTH
Charles
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Good thinking - the Ezi Out stud also stops the nipple from being
crushed and any deformation of the nipple helps you apply
more torque via the Ezi Out.
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Whilst I have never tried this it has been suggested before....
Weld a nut of suitable size over the the nipple. This will then have a greater diameter with the unworn flats giving a better grip to a suitable socket.
It maybe that that the localised heating also has a beneficial effect. I imagine MIG is preferable as the heating will be very localised, with less risk of colateral damage.
pmh (was peter)
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Clear all the rust.
Hit the screw end-on fairly sharply with a hammer, about hard enough to start to compress the end, but no more.
Find an old ring spanner that is a bit too small, and force it on by tapping a larger socket over it.
Apply the tiniest of anticlockwise force, JUST enough to move the screw, not enough to shear it (easier said than done !).
If it won't move, hit it again while the strain is on.
If you can get it to move the merest fraction, apply more Plus-gas and then leave it for a few hours.
Go back and RETIGHTEN it, then undo it again. Gradually work it backwards and forwards.
It is not guaranteed, but has worked for me on about 7 out of 10 ocasions.
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