Dragging front drivers side brakes

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Short Version

Having trouble getting the piston dust boot off.

Any tips?

Also, any opinions on potential benefit of beefing up the pad return springs?

LONG VERSION

My drivers side front wheel is getting hot, and the brakes (Daihatsu Skywing FWD with floating single-pot calipers) seem to be dragging. Jacked up with the wheels off at idle in 2nd gear, that side doesn't rotate. Feeding a bit (not a lot) of brake pressure in to transfer some drive to the stuck side gets it moving, so its not VERY stuck, but its stuck enough to be a problem.

Have already cleaned up the slider pins and pad guides, and swapped the pads side-to-side, to no avail. Its got a new brake hose that side, but I've used PTFE tape on the outer threads of both the brake hose and the bleed nipple. I was pretty careful to avoid it getting into the plumbing and acting as a non-return valve, and opening the bleed nipple doesn't free off the wheel, so I don't THINK that's the problem.

So I reckon I've got to take the caliper apart and clean it up (or replace it, IF available). I've taken it off, but have so far not been able to remove the dust boot, though I may have already damaged it trying.

The Daihatsu G100 manual (Not the same car, Skywing seems to be mostly like a G11, but probably close) says:-

"Detach the cylinder boot set ring and cylinder boot, using a common screwdriver"

which seems to be easier said than done.

Other (non-make specific) sources vary, from the realistic/defeatist "cut away the dust seals" (perhaps implying that it isn't possible to get them out intact, at least on Rovers)

http://www.head2head.free-online.co.uk/Rover/caliper.htm

to the standard-issue insane optimism of "Remove the outer dust seal, too." (Yeh, thanks for that piece of "useful" advice)

http://www.popularmechanics.com/cars/how-to/a3915/4305927/

Eric the Car Guy seems to leave them in place, and just blows the pistons out through them with compressed air.

https://www.youtube.com/watch?v=I4FzXGrSrmU

I don't have compressed air, so my options for removing the piston (whether or not I get the dust boot off first) seem to be:-

(a) Take it to a filling station that has air (rather a lot of them in these parts don't)
(b) Find my old brake hose and hook it up (duct-tape may feature) to a bicycle pump
(c) Put it back on the car and blow it out with the brake pedal.

So, two questions:-

1. Any tips for the disassembly process, especially dust boot removal?
2. Any opinions on improving brake retraction, to avoid dragging brakes?

Eric and several other sources state that piston seal distortion is responsible for pad retraction, though this seems to be controversial.

http://www.ex-500.com/index.php/topic,40153.0.html

My pads have return springs on them, though they don't seem to be very strong. Would replacing or supplementing these be worthwhile?

I think I've seen some mention of this being done in the context of hyper-mile-ing. Can't find it now but havn't looked very hard since I don't think there were any details in the post.
 
option "C" is the safest method IMO, compressed air can create a flying hazard.
Some dust seal designs require piston removal to replace the seal.
Good luck

Smoky
 
Thanks.

I tried "shop air" at a couple of places, but the air guns available didn't have a cone-fitting on the end and I perhaps wasn't getting a good enough seal with plastic wrapped around the nozzle.

Sprayed brake fluid around a lot but didn't budge it. This brake fluid was pretty rusty (despite extensive flushing fairly recently) so it probably isn't very pretty inside.

I'll try it with tape around the nozzle, then try it back on the car. Havn't found my old brake hose yet.

A possible plan D, since there's a lot of air in it now, might be to put it in boiling water, if I can block the brake hose connection, say with a closely fitting bolt/PTFE tape, though the correct thread might be hard to find.

I'd ideally want to be quite a long way away when I did it. There's an open-air BBQ site on campus, with overhanging mango trees, that might have possibilities.

If I use a lot of water, that should help contain any projectiles, opening scene in Saving Private Ryan notwithstanding.
 
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2nd thoughts on plan D, thermal expansion of the trapped air seems unlikely to generate enough pressure (though I havn't done any sums), unless the heat frees things off, which is probably unlikely.

IF I could contrive to get liquid butane into it (also probably unlikely) that might do the trick.
 
You can't just trade in the caliper?

I don't see much point in taking a caliper apart unless new seals are available for it. So you would just rip the dust boot and replace it with the new one from the re-seal kit.
 
Originally Posted By: mk378
You can't just trade in the caliper?

I don't see much point in taking a caliper apart unless new seals are available for it. So you would just rip the dust boot and replace it with the new one from the re-seal kit.


Dunno yet.

In general in Taiwan, most parts (apart from consumables like oil filters) are impossible to source yourself, since there is no DIY, and the trade is a closed shop. You need a contact, like a "friendly" mechanic, though there's likely to be a stiff markup if you're not giving them the work.

This car is old and now very rare, but not a classic, which doesn't help.

I had a private student who was President of Ford Taiwan, who would sometimes pull rank on the Ford Parts Department to get me Daihatsu parts (This would, of course, normally be impossible) , but I've lost touch with him.

Seems to me its worth a try taking it apart and cleaning it up. If I can't do that without destroying seals, then I'm no worse of.
 
Plan E (extreme variant of plan D)

Harness The Power of The Chip Pan

Put water in it, and drop it in very hot vegetable oil.
 
Originally Posted By: Ducked
1. Any tips for the disassembly process, especially dust boot removal?

Sounds like the caliper is already off the car, which is unfortunate.

You need to remove the piston before you can remove the dust boot.

It is NOT necessary to use compressed air to remove the piston!

Obtain a set of Channellock pliers (or similar). Using the pliers, grab the piston along its edge and UNSCREW the piston from its bore. You're turning and pulling at the same time. There are no actual screw threads, of course; you create the "unscrewing" effect yourself. Once the piston is out, the boot will be trivial to remove.

If the piston is rusty (the usual cause of sticky pistons), it may take some effort to get the piston to rotate; and you don't want to be re-using such a piston anyway.

No idea what your hardware market is like in Taiwan, so I post this image to show you what "Channellock pliers" are:
79fa0246-8cd4-43b4-8898-1e3a599fe4eb_400.jpg


And -- silly question -- wouldn't it be easier to just order a replacement caliper from someplace like Australia?
 
Originally Posted By: Tegger

Sounds like the caliper is already off the car, which is unfortunate.


Easy enough to put it back. Plan C (IIRC) is to do that and push it off using the brake pedal.

Originally Posted By: Tegger

You need to remove the piston before you can remove the dust boot.

It is NOT necessary to use compressed air to remove the piston!



Recommended procedures vary (see first post) but, having tried removing the boot first (as the closest Daihatsu manual I have recommends), I tend to share your opinion on piston-first.

Originally Posted By: Tegger


Obtain a set of Channellock pliers (or similar). Using the pliers, grab the piston along its edge and UNSCREW the piston from its bore. You're turning and pulling at the same time. There are no actual screw threads, of course; you create the "unscrewing" effect yourself. Once the piston is out, the boot will be trivial to remove.



Tried that with mole grips and it didn't work. I have some water-pump pliers (usual British term for the same thing) somewhere so I'll try it with them.

They might give more rotational leverage because of the crank. Thanks for the suggestion.

Originally Posted By: Tegger


If the piston is rusty (the usual cause of sticky pistons), it may take some effort to get the piston to rotate; and you don't want to be re-using such a piston anyway.



Probably I'll end up replacing it, if I can get one, but a short term fix might be required since its due for 6-month inspection pretty soon.

Originally Posted By: Tegger

And -- silly question -- wouldn't it be easier to just order a replacement caliper from someplace like Australia?


Dunno. Shipping charges are probably quite high, but an overseas order might be a (last-resort) option.

Australia specifically doesn't have this car. Its probably the same part as the G11 but I don't know that for a fact.
 
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Originally Posted By: Ducked
a short term fix might be required since its due for 6-month inspection pretty soon.

If you can manage to eject the piston sufficiently, a short-term fix can be obtained by injecting silicone grease under the dust boot, smearing it on the piston surface, then working the piston in-and-out a few times. This will slick-up the piston and may help improve its ability to return home better than it was before. But that will depend on the amount of rust on the piston...

Some automakers (e.g.: Toyota) use lithium-soap grease on the piston rather than silicone. This tends to result in far less corrosion and sticking problems. Why other manufacturers don't do this is a mystery to me.
 
Originally Posted By: Tegger
Originally Posted By: Ducked
a short term fix might be required since its due for 6-month inspection pretty soon.

If you can manage to eject the piston sufficiently, a short-term fix can be obtained by injecting silicone grease under the dust boot, smearing it on the piston surface, then working the piston in-and-out a few times. This will slick-up the piston and may help improve its ability to return home better than it was before. But that will depend on the amount of rust on the piston...

Some automakers (e.g.: Toyota) use lithium-soap grease on the piston rather than silicone. This tends to result in far less corrosion and sticking problems. Why other manufacturers don't do this is a mystery to me.


Thanks for the suggestions.

Its difficult to find any specialist greases here in Taiwan, but I scored some silicone "brake grease" (well, that's what I asked for anyway) in a motorcycle shop on my last-but-one trip to Japan.

Labelling on the tube is all in Japanese, and IIRC (either from translation or from the packaging, which I dont have to hand) the temperature range was a bit low for a brake grease, (might be dielectric grease) but better than nothing.

Last trip I got some "rubber grease". No details available but I'd guess it might be a castor oil base, like the trad "red rubber grease" Castrol makes/made.

I thought standard lithium soap grease wasn't rubber compatible?

With pitted motorcycle forks (which seems a similar problem) I've had some apparent success using aluminium foil as an abrasive, lubed with sunflower oil. Pits get filled with aluminium paste in veg oil, and the veg oil sets (though slowly).

With electrolytic cleaning and careful flatting with a slip-stone, I think this technique might be improved.

Soldering might also have possibilities, but I havn't tried it.

I have tried Araldite (fast, couldn't get slow-setting) and super glue but couldn't get anywhere with either of them.
 
Originally Posted By: Ducked
Last trip I got some "rubber grease". No details available but I'd guess it might be a castor oil base, like the trad "red rubber grease" Castrol makes/made.

That could work. All you'd need is something that's compatible with your polymers and is slippery.

Originally Posted By: Ducked
I thought standard lithium soap grease wasn't rubber compatible?

Depends on how you formulate your polymers, no?

Another silly question: Rather than trying to DIY what appears to be unDIY-able, why don't you just let a garage replace the caliper? Wouldn't that be a lot faster and easier?
 
Originally Posted By: Tegger


Originally Posted By: Ducked
I thought standard lithium soap grease wasn't rubber compatible?



Depends on how you formulate your polymers, no?


Probably. But I don't formulate the polymers.

Originally Posted By: Tegger


Another silly question: Rather than trying to DIY what appears to be unDIY-able, why don't you just let a garage replace the caliper? Wouldn't that be a lot faster and easier?


Defeatist talk, and would involve finding a garage here that I would trust to do a brake job.

But it may come to that.
 
Had another go with air, this time with pvc tape around the air gun nozzle

No dice.

Cleaned-up the caliper a bit with coke-can in a drill. Cleaning per-se fairly pointless but I had a faint hope that the vibration would loosen things up a bit.

Couldn't find my water-pump pliers, so put it back on the car for Plan C (brake pedal). Dribbled some fluid past the dust boot, bled and flushed with a syringe (in-and-out cycling of about 20 mls stirred up a fair bit of rust but it had probably already been loosened by the shop air.)

Now about half-extended but it still wont move with mole grips. Will need to find my opened bottle of brake fluid (or buy more) before I can push it further with the brake pedal.

Or find my water pump pliers and try them.

Using the brake pedal to do what it is designed to do was a lot easier and less messy than the standard recommended method,(air) which didn't work.

Go figure.
 
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OTOH, I MIGHT have damaged the master cylinder seals, either through back-pressure generated by the syringe (an alleged flaw of this method) or due to excess pedal travel as the piston let go.

Then I'd not be so smug.
 
Originally Posted By: Ducked
Dribbled some fluid past the dust boot,

What? One does not add fluid through the dust boot.

I don't think you should be doing mechanical work on your car.
 
Originally Posted By: Tegger
Originally Posted By: Ducked
Dribbled some fluid past the dust boot,

What? One does not add fluid through the dust boot.



One might, if one considered that brake fluid was a penetrating lubricant, and one had need of some penetrating lubricant in that location.

One might consider this a variant on the advice one had received to apply grease (perhaps more effective, but much more difficult to get to where it might count), in that location.

Or one might not, because one had never heard of anyone else doing it.

Depends on who one is, really.
 
Originally Posted By: Ducked
Originally Posted By: Tegger
Originally Posted By: Ducked
Dribbled some fluid past the dust boot,

What? One does not add fluid through the dust boot.

One might, if one considered that brake fluid was a penetrating lubricant, and one had need of some penetrating lubricant in that location.

Were brake fluid a penetrating lubricant, would one not have this problem with a sticky piston in the first place?
 
Originally Posted By: Tegger
Originally Posted By: Ducked
Originally Posted By: Tegger
Originally Posted By: Ducked
Dribbled some fluid past the dust boot,

What? One does not add fluid through the dust boot.

One might, if one considered that brake fluid was a penetrating lubricant, and one had need of some penetrating lubricant in that location.

Were brake fluid a penetrating lubricant, would one not have this problem with a sticky piston in the first place?


Too hypothetical for me mate. AFAIK there was no brake fluid ahead of the seal before I put it there, because the seal was still, like, sealing.

Now there is.

Dunno if its done any good (the main resistance is probably rust behind the seal, and it won't have made any difference to that) but I can't see why it would do any harm.
 
Originally Posted By: Ducked
AFAIK there was no brake fluid ahead of the seal before I put it there, because the seal was still, like, sealing.

I think that doesn't say much for any alleged penetrative properties of brake fluid. If brake fluid had penetrative properties, would it not have been present on the outside of the hydraulic seal if rust were present? Or is this thought also too hypothetical?

Originally Posted By: Ducked
Dunno if its done any good (the main resistance is probably rust behind the seal,

Rust on the piston itself. Rust on the bore will have little to no effect. THIS is what sticks-up a piston:
01.jpg


You can go on a voyage of discovery for yourself and see if your piston is similarly decorated.

Originally Posted By: Ducked
I can't see why it would do any harm.

No harm, but it did make an ineffectual mess for you, which silicone grease (or red rubber-grease) would not have done.
 
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