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Phil the Fluter
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Joined: 10 Mar 2018
Posts: 52



PostPosted: Tue Aug 06, 2019 4:42 pm    Post subject: O/S/R Brake Locked On. Reply with quote

I have a 1987 3.2 Carrera that does almost nothing but sit inside my garage. The only exercise it's had over the past few years is a monthly trip up and down my 20-yard driveway.

Some time ago, I noticed that although it seemed to drive perfectly well on my driveway, it was reluctant to roll under its own weight on a slight slope.

I jacked it up and found that the offside rear wheel is impossible to turn by hand.

Presumably, the caliper pistons are stuck?

I tried to take the pads out in order to try to free the pistons but, before I can remove the pads, I have to tap out the retaining pins. My problem is that I've been told each of the two pins is held in place by a tiny retaining pin but I cannot see anything resembling one of these little pins. I've done this job on a number of other (non-Porsche) cars so I know more or less what sort of thing I'm looking for.

As far as I can see, there is nothing holding the retaining pins in place and I can see no little hole in either pin from which a tiny retaining pin might have been removed at some stage.

I haven't tried tapping them out because, if there is something holding them in place, I don't want to do any damage.

Any advice would be much appreciated.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Tue Aug 06, 2019 7:50 pm    Post subject: Reply with quote

Pictures attached of the two types , and i'm not sure which type you have , either the horse shoe locking pin or the pin with an expandable head .

Basically if no horse shoe then these just knock out with a punch / drift .

You also have the handbrake which might be the issue .. if with pads removed its still tight then obviously it's this .

Bottom image and you just knock them out .
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Phil the Fluter
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Joined: 10 Mar 2018
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PostPosted: Tue Aug 06, 2019 8:27 pm    Post subject: Reply with quote

Thanks, deMort.

The upper pic (with the clips) is what I was expecting but there are no clips.

The bottom pic looks much more like it.

I think I'd prefer to have those little clips. It would make me a lot more confident that the retaining pins weren't going to slide out of the caliper and go bouncing down the road. Surprised

I hope the problem doesn't lie with the handbrake as it seems that's a much more complicated repair job.

Again, many thanks.
 
  
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Phil the Fluter
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Joined: 10 Mar 2018
Posts: 52



PostPosted: Wed Aug 07, 2019 10:48 am    Post subject: Reply with quote

The bottom image (above) was indeed correct.

I have now knocked both retaining pins out but the pads simply will not move when I try to take them out.

The pads can't be stuck to the disc because the wheel will turn when the car is driven in a normal fashion via the engine, even though I can't rotate the wheel at all when I try by hand.

It seems as if the pads are pressing hard enough against the disc to stop me turning the wheel by hand but not hard enough to stop the wheel turning when under engine/gearbox power.

What should I do?
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Wed Aug 07, 2019 7:26 pm    Post subject: Reply with quote

Ok .. a possible seized caliper piston or the pads are jammed in the caliper due to corrosion ..

At work i would be using this ..

https://www.ebay.co.uk/itm/Disc-Brake-Pad-Spreader-Separator-Caliper-Piston-Professional-Car-Hand-Tool/183072440208?epid=10014858340&hash=item2a9ff7bf90:g:AKcAAOSwMgdXyTUs

remove the pins , remove the metal tab that puts pressure on the pads then use this to push back the pads .. just use it behind the metal parts of the pads .. you are trying to push them apart basically and force the caliper piston into the caliper .

If you're lucky then its a case of forcing the pads out ( they have rusted in place ) .. a bit of sanding on the metal edges of the pads then refitting .. ally grease on the metal parts that sit on the caliper .

If unlucky then its a seized piston in the caliper .. either a new or refurb caliper is needed .

The pins like you have never come loose ... trust me so horse shoe clips are not needed .
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Phil the Fluter
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PostPosted: Wed Aug 07, 2019 7:43 pm    Post subject: Reply with quote

Thanks for the speedy reply.

I've ordered the special tool.
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Thu Aug 08, 2019 6:22 am    Post subject: Reply with quote

Phil, you have discovered one of quite a few issues that can arise when machinery is laid up as opposed to being made use of.

Iain, (DeMort) great pics of the components..

Phil, I have suffered similar brake issues though more down to wear and tear such as the calliper dust seals being torn allowing damp and road crud to cause the brake pistons to corrode and thus jam in their bores... When you get your pads out it might be worthwhile to check on those dust seals for tears...

The common problem is that if the pads are worn down considerably the piston is extended further out of it`s bore and if the dust seal is damaged the bright metal surface of the piston can become pitted, and if the piston is forced back into the cylinder the pitting on the piston causes it to stick in it`s bore to some extent... The pressure applied to the brake pedal will overcome the the jamming effect of the corroded piston to allow the brake to operate as such... However it is unlikely that the piston will retract as required when the brake pedal is released causing the pad to remain in contact with the disc, and create a similar situation to the one you are suffering at the moment..?

Of course a similar situation can arise in the circumstances which you describe relative to your lack of use of your 911... there will be inevitable corrosion on the calliper and pads restricting their free movement, add that to the possible situation described for the piston and you can begin to understand why brakes can stick on... perhaps more so when you park the car you put the brakes on to stop it and at that stage the pistons are extended to operate the brake but may or may not retract to any degree and the pads now in contact with the discs, stay in contact with the discs held there by the corrosion build up between the contact areas of the pad to the calliper... and in a worse case corrosion on the pins restricting free movement of the pads on the pins too... Yup laid up brake systems are unlikely to be operating as they should...

Of course if attention is not paid to these simple details and you take to the road ignorant of the possibility that you had a lightly sticking pad or pads, the effect of which you did not actually detect as restricting forward progress and you drive off it may not be long before you suffer brake failure.... the friction created by the rubbing pad(s) can overheat the brake fluid to the extent that it boils, and when you apply the brakes there are none to be had...!!!! You need to be pumping FAST to get a pedal back and derive a measure of braking...

Of course if you are tuning into any of this, then it should be obvious why you should not lay up a car with the handbrake on more so in a damp climate...

Perhaps best to sell me your 911 if you don`t use it Phil, the old thing is dying quietly... Smile

Hope this ramble helps in some way... Question
 
  
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Phil the Fluter
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PostPosted: Thu Aug 08, 2019 6:41 am    Post subject: Reply with quote

Thanks for your input, Luddite.

You make several interesting and very useful points, all of which I shall take on board.

Purely for information purposes, the brake pads are nearly new (in terms of wear) even though they are several years old. On that basis, the pistons won't be poking very far out of their bores.

I bought the car in 1989 with 34,000 miles on the clock.

It now has 52,000 miles on the clock.

It was last on the road in 2007 and in that year it covered just 400 miles.

Why did I drive it so little? Mainly because my partner hated travelling with the top down as it messed up her hair!
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Thu Aug 08, 2019 7:05 am    Post subject: Reply with quote

Phil, I am really pleased that you found some value in my ramble.

I had no right to poke fun at your situation, I bought my old car in 2002 with 8k on the clock put circa 25k miles on it up till 2006 and it did a very few miles over the next few years up to 2014 from then till last month it never turned a wheel, it was not my wife`s hair that caused the lay up but her desire for me to self build a home extension doubling the size of our house to provide all the mod cons that ladies desire big kitchen en suite, sun room, patio and on and on and on...then bring the old part of the house up to similar levels of comfort.... An appointment at a top end hairdresser after every run in your 911 out would be a cheaper and less stressful than that which I was into to keep her ladyship happy... Did I mention the landscaping.... Sad

Hope you get your brakes sorted out... perhaps one of those furry Russian military hats, or a leather flying helmet and goggles as it seems some Morgan drivers are into... Floor
 
  
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Phil the Fluter
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Posts: 52



PostPosted: Sat Aug 10, 2019 1:29 pm    Post subject: Reply with quote

The special tool arrived this morning.

I tried to move the pads back by putting the tips of the lower edges of the plates of the tool behind the upper/metal parts of the pads but the pads wouldn't budge and one of the plates bent in the process.

The lower edges of the plates are some distance from the screw mechanism and so the "lever" effect was considerable and obviously too much for one of the plates.

I then had the bright idea of putting one of the top corners of each plate behind the upper/metal parts of the pads. In that position the lever affect is significantly less – quite small, in fact – and so almost the full force of the screw was applied to the tops of the pads.

That did the trick and the pads moved back enough to relax their grip on the disc.

I then pressed the brake pedal and the pads gripped the disc (as you might expect) but refused to let go of it. I was, in effect, back to square one.

I used the special tool again and eventually managed again to move the pads back a little.

With some effort, I was then able to remove both pads.

With both pads out of the way, I was able to investigate the action of the pistons inside the caliper.

Using a long piece of wood, I pressed the brake pedal while keeping my eye on the pistons: I couldn't budge them.

I then put something between each piston and the disc in order to stop the pistons popping out completely, climbed into the car and I pressed the brake pedal several times with my foot.

Returning to the rear of the car, it was clear that the inboard piston simply wouldn't budge and it appears to be seized rock-solid. The outboard piston did move but, when I used the tool to push it back into its cylinder, it seemed very reluctant to move. I'm not an expert on this subject but I've changed disc pads before (not on a Porsche) and this piston certainly didn't move anywhere near as freely as I would have expected based upon previous experience.

Advice regarding my next step(s) would be appreciated.
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Sat Aug 10, 2019 3:13 pm    Post subject: Reply with quote

GREAT to see you are game to give it a go Phil... I looked at the tool and kinda guessed you might struggle with it...I use far more primitive means..

Off to type something up for you in the hope YOU will resolve the issue... NO great skill required I have confidence that you have what it takes to resolve it yourself with a little more help..

I have used mole grips and a claw hammer, you already have a bit of wood... so we are ok for that at least.. Floor

It takes me a while to think and type at the same time, but at least I can use two fingers.. Grin

Back in a while..
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Sat Aug 10, 2019 3:22 pm    Post subject: Reply with quote

Basically you have a seized caliper piston .. it needs replacing or a strip and refurb .. there are kits available i believe to replace the pistons .. my feeling is perhaps a new caliper would be better .

A quick search for a new caliper and ECP have a 37 % discount this weekend ..

https://www.eurocarparts.com/brake-caliper?gclid=EAIaIQobChMItvXmyMz44wIVyLTtCh1zeAFcEAMYASAAEgL7EPD_BwE

You need to check the details are correct for your car though .
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Phil the Fluter
Trainee


Joined: 10 Mar 2018
Posts: 52



PostPosted: Sat Aug 10, 2019 3:33 pm    Post subject: Reply with quote

deMort wrote:


A quick search for a new caliper and ECP have a 37 % discount this weekend ..

https://www.eurocarparts.com/brake-caliper?gclid=EAIaIQobChMItvXmyMz44wIVyLTtCh1zeAFcEAMYASAAEgL7EPD_BwE



I've checked out their website and a right rear caliper is £349.99 plus a £54.99 surcharge – which they'll keep if my old caliper turns out not to be repairable when I send it to them.

Using the 37% discount reduces the total price to £276.48

Looking around, I've found this one on another site for £175 plus VAT. With delivery, the total price is £221.99

https://www.design911.co.uk/pages/productList.aspx?search=caliper%20rear

However, checking the photo of the caliper, I'm not sure it's got any pistons in it. Surprised

Will you have a look and tell me what you think?

Last edited by Phil the Fluter on Sat Aug 10, 2019 3:46 pm; edited 2 times in total
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Sat Aug 10, 2019 3:45 pm    Post subject: Reply with quote

OK OK so here is a possible stone age way of resolving the issue at least to some degree, though bound to be frowned upon by Mr Porsche..(-:

You at least can get the pads out so the gizmo did what was asked of it, though looking at the design it seems to be more useful to push good condition pistons back into their bores having removed worn down pads, as opposed to trying to force stuck pads/piston combination away from a disc..? you made it work for you so whats more to want...?

Working on old cars requires a bit of lateral thinking which you have...(-:The claw hammer or the vice grips are tools that I have used to spread seized pistons/pads away from the disc... though as you can remove the pads no need to go into that..?

The problem as it stands at the moment is that one of the pistons is stuck in it`s bore.... Not entirely unexpected... With the other pad left in place, it is a simple matter of using the brake pedal to break the bond that the other piston has in it`s bore... however the amount of pressure you may have to apply to the pedal to free it, will cause the disc to be deflected to some degree by the piston that can move.... thus to stop this from happening it would be ideal if you can find something to fit between the calliper and the disc to inhibit at least some of that movement though taking care not to inhibit the stuck piston from moving when you apply pressure... As you have noted it seems less than ideal to pop the piston right out of it`s bore, so if you can avoid that...Great.

Yup, for sure you will be testing the whole system for weak points when you try to force that piston out, which is no bad thing, better to find out that rusty brake pipe was incapable of holding pressure NOW as opposed to finding out when braking in an emergency... Perhaps another possibility is that an old flexible hose could expand and fail... or seals in any cylinder.... but the latter would seem rather unlikely..(-:

Let us know how you get on, and if my stone age methods work for you we can carry on in the same vain if you like

Happy to bow out if any real expert determines you should act differently..

Good luck.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Sat Aug 10, 2019 3:47 pm    Post subject: Reply with quote

I've never heard of a caliper being sold without pistons before so i think it's just that they are black and not seen on the small picture .

You could always email them to check but i'm pretty sure it will be complete .

That seems a far better price than ECP !

EDIT .. there is also a discount code at the top of the page !
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Sat Aug 10, 2019 3:59 pm    Post subject: Reply with quote

While I was typing had not noted that Iain had joined in.... of course a reconditioned calliper is a far better repair process.

I shall bale out of the conversation other than to suggest..

Hope if you go that route you can free off the brake pipe,, wire brush and a spray with WD40 or similar, a few times before you try and if you are going that route best buy a proper brake spanner to give you the best chance of not damaging the brake nut if it is as tight as might be expected..?

Good luck. Thumb
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Sat Aug 10, 2019 4:28 pm    Post subject: Reply with quote

There's nothing wrong with a repair as you suggested , an airline down the nipple hole will often push out a piston ...

It will probably have a corroded bore though .. there is the cost of parts and indeed what tools you have at home... as a replacement caliper is not that expensive in the great scheme of things then that is what i went with.

It's just my opinion though and everyone should suggest what they think as i'm not keen on the posts where it is just me and the Op .. i don't know everything as i often say !
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Phil the Fluter
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PostPosted: Sat Aug 10, 2019 4:46 pm    Post subject: Reply with quote

Luddite wrote:

With the other pad left in place, it is a simple matter of using the brake pedal to break the bond that the other piston has in it`s bore... however the amount of pressure you may have to apply to the pedal to free it, will cause the disc to be deflected to some degree by the piston that can move.... thus to stop this from happening it would be ideal if you can find something to fit between the calliper and the disc to inhibit at least some of that movement though taking care not to inhibit the stuck piston from moving when you apply pressure.


Hi Luddite,

Thanks for the suggestion – I've just tried it.

Having digested your caveats and with the pads still removed, I put the special tool into the caliper with the plates sufficiently far apart that they would allow both pistons some movement without either piston being able to pop out fully or exert any pressure on the disc (as any moving piston would simply press on the plate of the tool which, in turn, could not contact the disc because the other plate would stop it moving far enough to do so).

However, the seized piston simply didn't budge after several very firm presses on the brake pedal.

As for the other piston, it did move as far as the plate would allow it but to get it to retract again took a lot of pressure via the special tool.

This "only just movable" piston will press the pad against the disc when the brake pedal is pressed but, when the pedal is released, the braking effect of that pad continues – as the piston simply won't retract.

Whatever is affecting the movement those two pistons is affecting them very badly indeed.

What a life! Rolling Eyes
 
  
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Phil the Fluter
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Joined: 10 Mar 2018
Posts: 52



PostPosted: Sat Aug 10, 2019 5:02 pm    Post subject: Reply with quote

deMort wrote:
I've never heard of a caliper being sold without pistons before so i think it's just that they are black and not seen on the small picture .

You could always email them to check but i'm pretty sure it will be complete .



Thanks, deMort,

I've just emailed them to make sure their caliper is a straightforward replacement for the one I'm taking off.

Regardless of how this repair progresses, I must say I'm very grateful indeed for the helpful advice received from you and Luddite.

I really do appreciate it.

Thumb
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Sat Aug 10, 2019 7:38 pm    Post subject: Reply with quote

Iain, we operate in different worlds, well at least as far as work in the garage goes...(-: I feel that I know the kind of good hearted guy you are and believe me I have learned so much from your posts... THANKS.

I have never bought a new calliper and have brought many an old abandoned banger back to life that has lain for many a year.... However there is no arguing that a fitting a reconditioned calliper is the simpler and most effective option, but to me that requires little skill and perhaps more importantly no real need to learn about and thus understand the system and it`s likely failings.

Sure any garage business has to repair as quickly and efficiently as possible, and unit replacement is the way to go..there is no time to strip a rusty calliper down and clean it up in the hope that it will work for a while at least.... but it might not work at all... time wasted for a less than guaranteed outcome...definately not the way to go for a garage.

Me..? I was repairing my old cars a pound at a time, so if there was any chance I could repair something by stripping it down to find out how it worked, and reassemble it, then that was the way to go, sure I broke a few things trying to strip or repair them but boy did I learn a lot in the process.... That was long before the easy money or plastic debt days...Thus a measure of attitude towards self reliance was a pre-requsite and more so if I wanted to run sports cars and m/cycles on my budget..

As ever I have a story (-: ... A few years back Porsche 911 SC Sport pal who had stored his car for a while and is handy with tools, sent off his front callipers for repair/replacement, got them back all nicely painted, fitted them and bled the system, the brake pedal was seemingly as spongy as it was before he sent them off for overhaul... He sent them back as faulty, they were tested as being OK and sent back, he refitted them... same outcome.. he called me in frustration... rolling around the ground... I clamped off each of the flexibles till the pedal went hard when pressed as opposed to spongy... Just as in the case of Phils rear calliper, one of the pistons was siezed, though the other was free to operate... the spongy feel was not air in the brakes but the disc being pushed to one side by the operational piston/brake pad and the disc springing back when the pedal was released.. the disc could be seen flexing when the pedal was pressed... He just did not want to believe that could be the issue... shrug! Even on the test drive he agreed the brakes were "better" but surely that could not have been the issue...!!!

I very much doubt the calliper bores will be corroded unless the car has gone swimming, the pressure seal stops water entering the area of the bore, though VERY old brake fluid can contain a degree of water and could perhaps cause a bore to become rusted...? Though I bet Iain has seen hundreds more callipers than I..

The more usual scenario I have come across is that the piston gets corroded, if of the chrome plated type, though these days it seems they use better quality materials or perhaps machining can produce smoother piston surfaces in times past..?

The reason I have found for piston corrosion or pitting is usually that the dust seal has failed and water/crud can access the polished surface of the piston, more so if the pads are worn and more of the pistons surface is exposed to the crud..

Another problem arises if the now slightly pitted piston is forced back into the bore in order to fit new pads, what are the chances the pitted piston will operate freely enough to release all pressure on the pad.... perhaps creating problems of a slightly dragging brake or indeed sticking on..

The other issue resulting from a damaged dust seal, can be that the area of the bore in the calliper to the outside of the seal corrodes due to the same crud entering that could have damaged the piston... and as such can grip the piston slightly adding to the degree of resistance to the piston retracting normally...? To attend to this the piston requires to be removed and the rust cut back, emery paper can achieve that.

Strange as it may seem I have in the last few weeks got round to fixing the same issue on my old and now rarely used Ford p/up truck... intermittently sticking front brake... removed the pads, extended the pistons as far as I dare, pushed back the dust covers and polished the few pits found on the pistons with fine steel wool... blew away any residue, and gave things a squirt of WD40 and pushed the pistons right back in and then back out again quite a few times to excercsise the pistons, then fitted 28 quids worth of new pads....obviously cleaned the interface area betwix pads and calliper and hit the pins with a file to clean the rust off a bit of copperslip and the job done.... Pity I am scrapping the old thing in a few months... it helped build the extension I am sitting in typing at the moment...(-:

For sure a garage would have fitted a new Calliper and I would have paid out more than the old thing was worth...perhaps.

Phil I only type this to provide alternatives for those who may not have the cash to buy new kit and like me want to understand how stuff works..(-:

Be very sure that you have that car well supported slide the wheel under if you do not have blocks or similar because if you are removing the calliper the holding bolts may be very tight. and require a fair degree of leverage to shift them.... the last thing needed is for the car to drop to the ground and worse still with any part of you under it...

So Phil, you will end up with one reconditioned calliper out of four working as new... New pads pins and springs... perhaps....brake balance...? The reality is that there will be rather a lot of bits`n bobs that could probably do with being replaced with new, as opposed to one calliper.... perhaps flexy hoses or metal brake pipes... but how far do we go... at least you have been in there and hopefully had a look around....and now decided to strip and clean all the brakes...now that you are an expert on calliper replacement..(-:

Do buy the proper brake pipe spanner if you do not already have one, if you get the brake pipe nut out... GREAT, but usually crud gets trapped betwixt the nut and the pipe and sometimes corrosion starts there temporarily bonding the pipe to the nut and even if the nuts threads are not siezed, when you begin to unscrew it, the pipe may well twist and if you continue it will twist and break... New brake pipe required.... However IF you have wire brushed the assembly and sprayed with the stuff of your choice be sure you have also sprayed in between the nut and the pipe.... when trying to unscrew it if it seems to want to twist tap the pipe a few times spray it again and turn the nut back and forward a tiny bit while doing so to encourage the bond to brake.... good luck with that.. It could affect your costs if you damage the nut to make it impossible to screw out, thus requiring the brake "specialist" to drill it out and clean up the threads, the same goes for the bleed nipple, so again it might be worth hitting it with the wire brush and spray a few times allowing it to soak a bit before putting a tight fitting ring spanner or socket on it and trying to coax it out.... again if you mess that up, you give the brake guys a harder task and reduce the value if any to them of your old calliper...?

With both of the above proven to be free, then you are handing them a calliper with a sized piston.... perhaps they can say as a result it is not worth reconditioning or charge extra... So it may just be worth making sure it will come out by following the suggested stone age procedure.... Sure Iain, an air line can be used if there is a compressor available but in this case it seems simpler to just use the braking system (?) and in so doing testing it`s pressure holding capabilities by showing up any weaknesses should they exist...?

Hope this might help someone somewhere sometime if not you Phil.... Iain/DeMort is the expert in this area, I am just one who ever preferred muck around in a bid to be to be self reliant if possible...
 
  
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