O/S/R Brake Locked On.

Phil the Fluter · 6 Aug 2019

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.

deMort · 6 Aug 2019

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 .

Phil the Fluter · 6 Aug 2019

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.

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

Again, many thanks.

Phil the Fluter · 7 Aug 2019

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?

deMort · 7 Aug 2019

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-Bra...858340&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 .

Phil the Fluter · 7 Aug 2019

Thanks for the speedy reply.

I've ordered the special tool.

Luddite · 8 Aug 2019

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...

Hope this ramble helps in some way... :?:

Phil the Fluter · 8 Aug 2019

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!

Luddite · 8 Aug 2019

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:

Phil the Fluter · 10 Aug 2019

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.

Luddite · 10 Aug 2019

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..

deMort · 10 Aug 2019

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-...MItvXmyMz44wIVyLTtCh1zeAFcEAMYASAAEgL7EPD_BwE

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

Phil the Fluter · 10 Aug 2019

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

https://www.eurocarparts.com/brake-...MItvXmyMz44wIVyLTtCh1zeAFcEAMYASAAEgL7EPD_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 rear

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

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

Luddite · 10 Aug 2019

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.

deMort · 10 Aug 2019

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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