Daihatsu Skywing - Coke can for brake caliper | Technical matters | Back Room Forum

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Mon 7 Mar 2016 05:53

Daihatsu Skywing - Coke can for brake caliper - edlithgow

SHORT VERSION

Having trouble getting the piston dust boot off.

Any tips?

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. 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)

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)

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

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

So, any tips for the disassembly process, especially dust boot removal?

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Mon 7 Mar 2016 06:59

Daihatsu Skywing - Coke can for brake caliper - gordonbennet

A caliper has to be really badly seized for me to consider stripping it fully, my method is to remove one pad, wedge the edge of a suitable lever in place and pump the brakes till the piston presses against the lever, then peel back one edge of the dust cover to inspect the piston.

If piston acceptable, i feed some proper brake grease onto the piston all the way round (cotton buds work well) and push it home, rinse and repeat several times and see what its like.

Using common sense it might be possible to remove the second pad also and pump the piston further out to lube more of it.

Nine times out of ten if the piston isn't corroded on its sliding edge doing this a few times will free it up nicely.

I also spend a good deal of times thoroughly wire brushing all sliders and grease them thoroughly, not forgetting any locating pins.

This is my standard annual, or if things are working well every other year, brake service regime, something that never gets done at the vast majority of main dealers during whats laughingly called ''servicing'' usually comprising of peering through or from behind the wheel and squirting brake cleaner at the things (where's the roll eyes smiley?), hence why so many brake calipers seize up fully and can require replacement from years 4 to 7.

Its worked well for me, the only caliper i've ever had to replace in all my years was on the Mitsi Outlander we briefly owned which had a full annual main dealer history, and brakes in typical never-been-serviced-once-properly-from-new condition.

If you still want to remove the pistons then i too would just pump them straight out, the dust seal seating groove will be caked in corrosion on the caliper, the seal should remove reasonably well once the piston is out, and you'll find cleaning the seal seat much easier with the piston out the way.

Actually a thought occurs, handn't come up with this before, i wonder what happens to said brake grease if you heat it enough to help it flow round the piston for lubing purpose? i might have an experiment with that meself to see if the lubing job with a semi seized caliper could be made better with a liquid grease...hmm, probably too high a melting point to be practical so would welcome comments.

Edited by gordonbennet on 07/03/2016 at 07:04

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Mon 7 Mar 2016 09:17

Daihatsu Skywing - Coke can for brake caliper - craig-pd130

Actually a thought occurs, handn't come up with this before, i wonder what happens to said brake grease if you heat it enough to help it flow round the piston for lubing purpose? i might have an experiment with that meself to see if the lubing job with a semi seized caliper could be made better with a liquid grease...hmm, probably too high a melting point to be practical so would welcome comments.

The heavy 'red rubber grease' that I use on motorcycle calipers and seals is glutinous stuff, I don't think it would be practical to heat it to try and get it to flow better as it may degrade the grease.

I have heard of people using ACF-50 anti-corrosion lubricant around brake pistons, as it just sprays on, is very good at 'creeping' by capillary action, and is safe on rubber seals etc. But personally I don't like the idea of the stuff potentially mingling with brake fluid with untested effects.

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Mon 7 Mar 2016 09:30

Daihatsu Skywing - Coke can for brake caliper - gordonbennet

Thanks for that, yes i suspect the red grease would change properties once heated enough to liquidise it, keeping it hot enough to inject it under the dust cover would prove to be a challenge even if it didn't affect the grease.

No, i won't be trying any lubes either, other than the correct grease, where it could contaminate brake fluid.

Edited by gordonbennet on 07/03/2016 at 09:40

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Mon 7 Mar 2016 09:52

Daihatsu Skywing - Coke can for brake caliper - edlithgow

Thanks both.

I've taken the caliper off, so I'll try the compressed air method first, though it does seem as if the brake pedal should be simpler, as its designed to do the job.

This car is 30 years old, and in Taiwan, so its seen some neglect, including some from me (I left the brake fluid unchanged for several years)

I'd be surprised if its ever been taken apart before, and I expect its in a bit of a state inside, though it has been flushed several times in the last couple of years.

Its difficult/impossible to find brake grease here, but I did get small tubes of silicone grease, and (red tube) "brake grease" (200 C) last time I was in Japan. The silicone was a lower temp (maybe 130 C, IIR my GF's translation correctly) and maybe too low for "proper" brake grease, though that's what the guy in the motorcycle shop seemed to be saying. Maybe it is "dielectric grease"

I expect the local Taiwanese mechanics use standard lithium grease, which isn't rubber compatible, but perhaps modern cars use synthetic rubber for the seals and you can get away with it.

Since the grease is fairly precious stuff locally, and I'm going to be cleaning up the internals, I won't use it as a disassembly lubricant.

I might dribble some brake fluid behind the dust boot. Should be fairly penetrative and rubber-friendly.

I'm thinking if I needed more/better lubrication while taking it apart I might try vegetable oil. Wouldn't do long term because it'd glue things up, but it should be rubber friendly and (unlike silicone) it should be possible to clean it off once the thing is apart.

Edited by edlithgow on 07/03/2016 at 09:59

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Mon 7 Mar 2016 10:07

Daihatsu Skywing - Coke can for brake caliper - bathtub tom

Have you tried using a piston retractor tool or G clamp to push the piston back and then using the brake pedal to push it out again?

I find this works in most cases for sticky pistons (but not for those completely seized).

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Tue 8 Mar 2016 01:44

Daihatsu Skywing - Coke can for brake caliper - edlithgow

Piston is out. Might try the G-clamp suggestion for the other side though. I'll probably need one to re-assemble this one anyway.

Compressed air just sprayed rusty brake fluid around, so I cleaned the caliper up a bit with coke-can in a drill chuck (obscurely satisfying, though probably pointless, but I thought the vibration might help a bit) then put it back on the car to blow out with hydraulic pressure. When it was about half way, I eased the boot back over the piston, pushing it back with chopsticks (bit of local colour there).

After the first rather sudden "give" I tried to use...er..short strokes, to minimise the risk of master cylinder seal damage.

A lot of gritty, rusty sludge in the caliper cylinder, but it cleaned up quite well. There was quite a lot of barrel corrosion ahead of the seal, and some light pitting of the corresponding part of the piston, but not much corrosion behind the seal, suggesting the sludge came from elsewhere, presumably master cylinder and/or pipework.

The piston had some black "varnish" stuff adhering, which I'd guess was transferred seal material. I removed most of this, and I suppose it MIGHT have been contributing to the sealing, so maybe it'll leak when I put it back together.

I put silicon grease behind the dust boot, but found it impossible to get the piston back in with the boot in place.

I thought of cutting it and using superglue after assembly, (which I'd already used to patch a hole made when initially trying to remove it), but the silicon grease (which is effectively impossible to remove) would probably have stopped that working.

Having nothing to loose, I tried harder, and was eventually able to loosen the circlip from its bed of heavy corrosion and get the boot off, without causing it much more damage.

Scraped out the boot-groove, but have to do some work now so it'll probably be a while before I try putting it back together.

Pictures tell the story. (WARNING: Not suitable for those with mechanical sympathy, like, say, Germans)

Caliper on first removal.

[url=www.servimg.com/view/18149521/145][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6310.jpg[/img][/url]

Back on car during piston removal with hydraulic pressure, after partial clean-up and failed attempts with compressed air.

[url=www.servimg.com/view/18149521/146][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6311.jpg[/img][/url]

Piston on first removal. Euew!

[url=www.servimg.com/view/18149521/147][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6312.jpg[/img][/url]

Bottom of piston on first removal. Euew! again.

[url=www.servimg.com/view/18149521/148][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6313.jpg[/img][/url]

Sludgy Cylinder Base

[url=www.servimg.com/view/18149521/149][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6410.jpg[/img][/url]

Cylinder Rim Corrosion

[url=www.servimg.com/view/18149521/152][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6413.jpg[/img][/url]

Cleaner Piston

[url=www.servimg.com/view/18149521/150][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6411.jpg[/img][/url]

Dust Boot Out

[url=www.servimg.com/view/18149521/151][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6412.jpg[/img][/url]

Dust Boot Seat Corrosion

[url=www.servimg.com/view/18149521/153][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6414.jpg[/img][/url]

Partly Cleaned Dust Boot Groove (Bore looks rusty but its mostly rust from the seating groove sticking to silicone grease)

[url=www.servimg.com/view/18149521/154][img]i84.servimg.com/u/f84/18/14/95/21/th/img_6415.jpg[/img][/url]

Edited by edlithgow on 08/03/2016 at 01:47

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Tue 8 Mar 2016 17:05

Daihatsu Skywing - Coke can for brake caliper - gordonbennet

You can tell that car hasn't seen road salt, i've seen worse calipers on 6 year old UK cars, especially if they've had annual main dealer non maintenance, in other words peered at.

Hope you can get a seal kit for it, i don't see any reason why you shouldn't be back to a fully functioning caliper, without leaks.

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Wed 9 Mar 2016 02:54

Daihatsu Skywing - Coke can for brake caliper - edlithgow

Hasn't seen road salt, but a previous owner was a surfer, so its pretty rusty by Taiwan standards, though mostly in the hatchback area, where he presumably dumped his salty gear.

I'll try and get a seal kit, but I have some hopes it'll work if I just put it back together.

If the components hadn't been salvagable (which was probably the way to bet) I think it was still worth taking it apart, because its been quite informative. For example:-

(a) Brake flushing has been almost completely ineffective at removing this muck. This suggests that taking the calipers apart should be a periodic maintenance operation on old cars, especially old Taiwanese cars.

Maybe one wheel a year?

(b) Despite the cylinder being full of rusty, gritty sludge, there was surprisingly little local corrosion inside the seal. This suggests it came from elsewhere, presumably the master cylinder and/or pipework. If I was in The Yook I'd be looking to replace the pipes with copper (I have/had an unused flare-tool in the Yook) but I dunno if that'll be possible here.

c) Arising from (a) above, now I know how to do it, I should do the other side (which is so far working OK) as preventative maintenance, BUT considering (b) above, I should work top-down and do the master cylinder next, which is frankly a bit scary.

Decisions, decisions.

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Wed 9 Mar 2016 17:13

Daihatsu Skywing - Coke can for brake caliper - gordonbennet

Master cylinders are usually simple affairs, but i wouldn't take one apart unless i could get a seal kit for it, you only need to snag the very fine edge of one seal refitting it to ruin it.

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Thu 10 Mar 2016 04:45

Daihatsu Skywing - Coke can for brake caliper - edlithgow

Master cylinders are usually simple affairs, but i wouldn't take one apart unless i could get a seal kit for it, you only need to snag the very fine edge of one seal refitting it to ruin it.

Thanks for the advice, and the excuse to put off this job, which I am a bit apprehensive about.

I will try it if/when I can get a seal kit though.

Another vexed, and perhaps controversial question:

I speculate above that local Taiwanese mechanics usually just use general purpose (probably lithium base) grease on brake components, (not unknown, in my experience, with British mechanics either) and that perhaps modern cars use synthetic (eg viton) rubber for the seals so this is OK.

I've heard "somewhere" that this is recommended by Toyota, presumably because lithium grease is a better and more corrosion resistant lubricant, and they know thier seals will stand it.

This car is over 30 years old, so I'd guess its seals might be more vulnerable. The closest Daihatsu manual I have (for the G100) says "rubber grease". but I wonder if the (rather surprising) lack of local corrosion inside the calipers is due to the use of petroleum base grease in the past.

I'm wondering if I should experiment with general purpse lithium grease on re-assembly, IF I can get a seal kit for it in case it doesn't work out.

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Thu 10 Mar 2016 10:01

Daihatsu Skywing - Coke can for brake caliper - Wackyracer

When I bought Viton O rings to repair a diesel fuel pump the company that makes and sells the O rings recommend using silicone grease.

I know alot of the people running diesels on veg oil use viton O rings as it is not affected by the veg oil.

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Thu 10 Mar 2016 11:38

Daihatsu Skywing - Coke can for brake caliper - edlithgow

When I bought Viton O rings to repair a diesel fuel pump the company that makes and sells the O rings recommend using silicone grease.

I know alot of the people running diesels on veg oil use viton O rings as it is not affected by the veg oil.

I find that puzzling on two counts

Firstly, though I don't know the detailed design, I'd expect a fuel pump O ring to be potentially exposed to petroleum-based diesel fuel, which is generally regarded as hostile to rubber.

If it IS so exposed, there wouldn't seem to be much point in protecting it from petroleum-based grease.

Perhaps the silicone grease isn't washed off by diesel and petroleum-based grease is?

Secondly, it was my understanding that vegetable oil was more rubber-friendly than mineral oil. Hence traditional Castrol "red rubber grease" is, I believe, castor oil based.

Edited by edlithgow on 10/03/2016 at 11:41

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Thu 10 Mar 2016 11:57

Daihatsu Skywing - Coke can for brake caliper - Wackyracer

I see what your thinking, usually the O rings fail when used with veg as the fuel pumps are old and cold veg oil is quite thick and places extra pressure on the old O rings. People replace with new Viton as they are better quality than what was fitted in the 1990's.

You could always ask the advice of specialists such as Bigg Red, I've found them to be very helpful and they might tell you what they use during re assembly.

Edit: www.biggred.co.uk/process.php

It seems they use silicone according to this article.

Edited by Wackyracer on 10/03/2016 at 12:04

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Sat 12 Mar 2016 23:54

Daihatsu Skywing - Coke can for brake caliper - edlithgow

Thanks for that. Didn't like the "hand pressure only on re-assembly or something is wrong" bit much. I needed a big G-clamp and a hammer, but I generally have trouble driving things like bearings in straight.

I used "a" silicone (labelling is all in Japanese, so I dunno if it was the correct silicone) when I put it back together yesterday, but that might have been a mistake, since the closest manual I have says "rubber grease" and the surprising lack of piston corrosion suggests it might not have been silicone (which I'm told has poor corrosion resistance) originally.

Couldn't find my rubber grease yesterday (generally disorganised, and in the middle of a house move) but I'll probably use it when I do the other side. An "accidental experiment".

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