Honda-SOHC
Other Stuff => Misc / Open => Topic started by: Lobo on January 19, 2023, 04:03:21 AM
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I’ve my old Kombi on axle stands, replacing the rear drum slave cylinders with new ones; and all brake lines drained down.
Q. What would be required to switch over to DOT 5 Silicon - eg is there a simple flushing product I can use - eg DOT 5 (S) itself? (I have no plans to change out the existing Master Cylinder, or indeed the front disc / caliper seals.)
Ta muchly in anticipation…
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Link >>> http://www.sohc.co.uk/index.php/topic,18973.msg167267.html#msg167267
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I'm guessing your vehicle has no ABS so draining down old fluid & then flushing with 5.0 should be fine.
Start bleeding from the furthest point to the nearest to the master cylinder. If you have a bleeding tool even better. Iirc the old fluid will be heavier than the 5.0.
Personally after using the vehicle for several journeys I would re-bleed a drop and check it for quality. Places like the master cylinder reservoir & brake balancer valves tend to retain some of the old fluid.
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Thanks Trig / Ted… interesting. Tbh, I have been t’internetting the subject in the past couple of hours with the general advice being to not bother due the possibility of incompatible seals, or causing issues due the two fluids ‘clumping’ (my word) and promoting blockages.
So more confused than ever, and given that the Master + front brake seals won’t be renewed I pondering whether to just play safe and stick with DOT 4; carefully topping the Master Cylinder through the access hole in the cab floor under the carpet. Wot could go wrong 😂.
Still happy to hear comments, my mind not fully made up; in case you’re wondering ‘why’ it’s just that 3/5 of the vehicles are now DOT 5 Silicon - ie it’d be nice to standardise.
(Interestingly, due Silicon not being hydroscopic, any included water apparently pools more easily, and towards the bottom of the system - causing worse corrosion issues. So I read.)
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Maybe the dot 5 will require more frequent changes. Interesting to drain it out into jar after a couple of years and see if there’s any water present.
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There can't be pooling as there is no emulsified water if you use 5.0 so where can the water come from? No water to boil off with 5.0. You can use Dot 5.1 as an alternative - I'm guessing it's not humid where you live so if you're worried stick with 5.1.
You can mix 5.1 with anything except 5.0.
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I guess Ted, said water comes from the same place as it does with DOT 4 - ie it just sneaks in there one way or another, accepting of course that DOT 4 is ‘actively’ hydroscopic. And we live right on water, so it is indeed humid at times.
Interestingly Johnny, that ‘precaution’ of more frequent changes with Silicon is indeed mentioned in what I’ve been reading.
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I have DOT 5 silicon in all my old bikes, some have had it in for the past 7 years and have read somewhere that it never needs changing .
DOT 5 is mainly used for classic cars and classic motorcycles. Since they do not run ABS and it is a really good application for these types of vehicles. In addition to this, this type of fluid prevents corrosion and this makes it perfect for bikes intended for long-term storage. So, if you have a classic car or bike, this is the right fluid for you. Though i did disassemble the whole system and cleaned and renewed everything before reassemble. You should always treat brakes as a whole system and after years any rubber parts are on there way out and passed there best ;)
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I guess Ted, said water comes from the same place as it does with DOT 4 - ie it just sneaks in there one way or another, accepting of course that DOT 4 is ‘actively’ hydroscopic. And we live right on water, so it is indeed humid at times.
Interestingly Johnny, that ‘precaution’ of more frequent changes with Silicon is indeed mentioned in what I’ve been reading.
Trying to work out how water might pool with Dot 5.0 fluid.
As you will know with hygroscopic brake fluids the water is absorbed from the atmosphere via the master cylinder venting system - this absorbed water then leads over time to corrosion and under extreme braking can boil in the brake caliper leading to loss of braking performance.
With Dot 5.0 not being hygroscopic the only way I can envisage that water might get into the brake system would be by condensation within the master cylinder top area - a very slow process I would imagine. If water is denser than the Dot 5.0 fluid I guess it could sink over time down the brake lines to the caliper - next time I'm bleeding my brakes I'll check if water sinks or floats in the fluid.
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When starting work on mine the front brake was useless, and after realising fluid had been leaking onto the disc, I replaced seals etc, which didn’t work. I then realised there was slight corrosion in the channel the piston seal sits in, and in the master cylinder bore. Barely noticeable, but I’m guessing minute traces of Dot 4 in those interfaces with the outside air attract water and then slight corrosion takes place over many years. As I couldn’t machine these I bought replacements and all now working very well, with the SBS501HF pads. They squeaked a bit, but I’ve slightly chamfered the leading edges, but also cleaned the disc with Wonder Wheels cleaner which may have helped, and if it has will use it periodically.
I just bought 250ml of ECB Dot 5 which I will not use, as I don’t want to do the full clean/rebuild (if the above is correct re the ‘interfaces’) which would need all old fluid cleaning off seals etc. (I got it for a good price £15.75 inc postage if anyone wants it for that!)
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Thanks all… very informative.
Trig, all brake seals (Master, front callipers, rear slaves) are <3 yo and not on their way out (I assume). Honestly, I’ve had enough monkey’ing around under her; I finish each day grimy and aching - getting too old for this malarkey. = don’t wanna dismantle the braking system. So… do ya reckon I could comprehensively flush the system with DOT 5 Silicon, and perhaps repeat in a month - would that do the trick?
I can’t afford ‘fails’ - the car has zero useful engine braking, and regularly comes down the local ‘mountain’ with engine @ max revs and brakes being ridden fairly hard (when she had 4x drums it was even more exciting with the burning smells). I’m awfully aware there’s no plan B at such times - fairly nail biting 😂.
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To answer the otiginal question, no I wouldn't change over as noted with original system still in place.
The risk is small, but you don't know the outcome, and none can state that clearly. That's for using the pre-used front end system and flushing the dot 4 out.
Don't know if there's enough upside in going to dot 5 to make it worthwhile, but each case is going to be different for each owner.
It's really just the corrosion potential as far as I understand it, none of the other properties seem to be large enough to hold sway really.
Current popular projection would have it that dot4 is so unstable as to be useless, that's just not the case and proven over so many years.
The bicycle world is absolutely stark staring nuts over this stuff, with plenty of opinions seeming to spill out of that sphere.
They have mineral oil as well in the equation, the exponents of which suggest anyone using dot 4 will die :) its amplified out of all proportion, and with many transferring that thinking to other vehicles. Those two are definitely, absolutely incompatible for interest.
Reading about one recently on mtb forum, Aus based car truck technician, got a test kit for checking water ingress and boiling point in brake fluuds, banging on to his father about having 9 year old dot 4 in his Toyota truck, thought he maybe at risk of dying ;D partly a joke in his writing, tested that fluid and surprised to find water inclusion very low, with boiling point well above minimum threshold.
As Ted notes, it's the arrangement around mastercylinder and how that is vented that gives the only scope for water ingress in practical terms. Decent system design will help with long term performance.
Converted systems dot 4 to dot 5 can scavenge any existing moisture of systrm if not going from dry assembly. Ending up at tge calioer ultimately. Specific gravity of most oils is lower than water.
Also the mtb crowd routinely seem to jet wash their calipers etc at about 50 trillion psi and may risk getting water past the piston seals that way. It wont ordinarily get through there in systems well maintained and not subject to external pressure.
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Lobo is the system servo assisted just out of interest?
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Lobo is the system servo assisted just out of interest?
With that disc front brake upgrade it should have some sort of pedal booster set up I would have thought.
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Lobo is the system servo assisted just out of interest?
With that disc front brake upgrade it should have some sort of pedal booster set up I would have thought.
Thats more dependent on mc and caliper bore sizes that should have bought more pure brake power in absolute terms.
The downhill scenario demands more cooling capacity than shear brake torque, that's normally through vented disc route. Can't see what's there in photo.
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Nope, no servo assist, and yep, whilst I haven’t, I do reckon I could lock the front brakes with effort.
I too was coming to the conclusion that it isn’t worth it, purely on the safety concern of ‘the unknown’ … coupled to the fact that the stopping power is minimal at best - in modern traffic there’s little room for error. Given that realistically, there is indeed little on-going maintenance with DOT 4; I should perhaps stay here.
Trig, the car indeed is a Classic, but realistically a genuine work horse, and used daily. I’m not overly precious about her; more than once I’ve had to go into the books to check the allowable axle loads 😂.
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Simon, is it a single bore mastercylinder pushing into whole system back and front too ?
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Yep Nige, single bore / dual reservoirs isolating front & rear brakes.
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Dot 5.1 is a synthetic based fluid developed for ABS systems for the small price difference I've gone to 5.1 on both our cars the bikes 5.0.
A lot is down to personal choice a good branded Dot4 is probably better than a cheap 5.1.
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I do think currently uninformed opinion demonising dot4 is giving a big skew to these things out on the great wide interweb.
All of them will work reliably and we sensible types on here can see the pros and cons of each in relatively serene surroundings :)
They really are nuts about it in cycles, but they do use something that could be of interest Simon. The use of syringes to dispense fluid is routine. That may offer you a very convenient access and fill option for your mastercylinder location as they are routinely using a pipe, sometimes with a little clamp to hold fluid while moving it about for convenient non drip use.
"Bleed kit" for Sram/Avid or Hope brakes which use Dot 4 / 5.1 fluids generally would have the appropriate seals for this application. they are not usually of any great cost.
Most of the others use mineral oil, a la Citröen system of old.
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Thanks to all who have contributed here; I do of course use the internet, but tbh place greater trust on the folk I know here as the knowledges and experiences will be genuine. I’ll be sticking with DOT 4 mainly due lack of current interest in spending more time on my back under the car (changing seals etc) - I’ve done enough for now! If next year I get the urge to change all the seals DOT 5 Silicon may yet happen.
I’ve a box of syringes Nige, and due the rear slave cylinders having the bleed nipples BELOW the brake pipes figured I’d give it a try to fill the lines ‘in reverse’, ie syringing in fluid from the slaves, and syringing the excess out from the master. It’s only me avail for this, so might work out easier. We’ll see… no biggy if proves unsuccessful.
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You may have such a device already, I make a brake bleed pipe/valve as follows;- thick wall small rubber hose (motor factors supply) that fits tight onto bleed nipple, push a bolt tightly into opposite end to seal it, then put a slit in one wall about 20mm long and roughly the same distance from clearing bolt end.
This makes the cheapest, best sealing little one way valve I've used to bleed with. Just open nipple 1/4 turn with this already in place, then you can pump as many times as you want while watching the reservoir level to bleed any line through. It's tradition that you may catch the outflow in a raspberry jam jar as part of this function :) strawberry being far too posh ;D
Used on any numberr of complex brake systems, such as pumped six way anti lock type with various nooks and crannies. Works very simply to never alow air to go backwards, so particularly efficient and quick to do on your own. You just don't need any assistance. That one way valve will let you walk round to the furthest point to lock it off as is doesn't need any monitoring.
It's so good, that should you need to replace fluid at any time, then if you can reach the bleed nipple without jacking, it will take about 5 mins a wheel.
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I’ve a box of syringes Nige, and due the rear slave cylinders having the bleed nipples BELOW the brake pipes figured I’d give it a try to fill the lines ‘in reverse’, ie syringing in fluid from the slaves, and syringing the excess out from the master. It’s only me avail for this, so might work out easier. We’ll see… no biggy if proves unsuccessful.
I think you will find the fluid friction makes it extremely difficult if not impossible to enable brake fluid to be pushed out of a syringe via a disc or wheel cylinder all the way via any three way connectors to the master cylinder on a car.
I've done it on my 400 (with 300 ml syringe) but that's just a relatively short set of pipework to the master cylinder.
What does work is if you use a large syringe (after initial first bleed using the brake pedal) to create a vacuum to pull out residual air bubbles. Using a syringe on an empty brake system has not worked for me as you can draw air in past healthy wheel cylinder seals. I've used an Easi-bleed kit to pump it down from the top if the master cylinder is cap vented only.
The valved bleed hoses mentioned above are pretty good you can buy them ready made - the hose lasts for over a decade.
.https://www.ebay.co.uk/itm/255004087399?epid=1130461392&hash=item3b5f6d9467:g:pNQAAOSws29bxgdw&amdata=enc%3AAQAHAAAAoD2Q6XcZob5YH4SOkrp7PuZUmC9MBofJv9KCOeKKUR1IW9V1BOzJqJ0NbflWhPZri%2BbP3E3Rn%2Bv6%2FtiN4nzkbAbuQzz%2FsxFq9kRlF0boDc4N5ANr8yZa3%2FWVyA61ZumqTUzI0vi3uYY5kRQUO94NJ56LKn09JBvmWncy72xtycDVrjJVgqqAkXAVp98x51zgcONk7oymr1BuBhZ2ewSwtrQ%3D%7Ctkp%3ABk9SR7CZoNC6YQ
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I make them longer Ted so that you can have a standard issue jam jar standing on the floor rather than try to balance it on something ;D
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I make them longer Ted so that you can have a standard issue jam jar standing on the floor rather than try to balance it on something ;D
I bought two pipes cut off the end stop & slit - joined with some Kunifer copper slightly angled brake pipe to get a similar outcome. 8) 8) 8)
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Thanks for the tips Nige / Ted - the rubber fuel pipe with slit worked perfectly, and with a mod to your jam jar using a 2L plastic milk bottle with interference fit on the hose. It consequently sits happily anywhere and at any angle - I bled all 4 corners in about 30 mins via the conventional method.
The car all buttoned up until next time - rewiring he mid year + likely engine out / new gaskets as a bit too oily tbh.
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Good outcome - fwiw my jam jar has now been upgraded to a see through thick plastic bottle (ex-PLJ) I think it was.
You mention - a bit too oily - what type of crankcase breathing system does it have if any?
When BL introduced the positive crank case breather system to the old A series engines it was a wonder cure - likewise on the old Opel 1900 cam in head engines.
Just thought I would put it out there for consideration.
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Good to get it all completed Simon. Those little tube make quite a difference in that it seals virtually perfectly and such a simple device too. They make even complex system very easy to bleed even new ABS etc.
Did you mean negative crankcase pressure Ted ? I thought they all pulled slight vacuum on the cases to avoid pressure trying to push oil out of any seals etc. It may have come from Buick V8 when they bought that as originally it was arranged this way, V8 being quite a windy arrangement in terms of case volumes vs piston volume and movement. I've a injected one now that has dipstick sealed which if removed you can hear the idle air valve compensate for the increased flow pulled through the cases.
We test them with a rubber glove on the oil filler to see if it inflates or sucks in assessing if working correctly. In bad cases the valley gasket is pushed upwards under the inlet manifold if they've not been looked after well, that because of pressure building up to much.
VW has many sealing faces with barrels, heads, pushrod tubes etc all individual components to seal too.
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Thanks Ted, a bit of lateral thinking that - never considered that.
Nige… somehow I’d have though exploding gases loaded up a crankcase pressure if anything vs dropping it below ambient - a bit confused here!
Ted - a breather next to the oil filler vents to the air filter, which is basically an oil bath used to trap particles. The upper 1/2 of the engine is ‘acceptably’ clean.
Below the air-flow baffling (ie ducted tin-ware over the cylinder heads) it’s a different matter - the lower engine is fairly damp with congealed oil. I’m guessing years of weeps as Nigel alludes to with chaotic air flow all making one horrible mess… (the lower engine is a bit wetter than the pic suggests)
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Thanks Ted, a bit of lateral thinking that - never considered that.
Nige… somehow I’d have though exploding gases loaded up a crankcase pressure if anything vs dropping it below ambient - a bit confused here!
Yes, i wasn't clear there. The cases venting into inlet tract on engine side of throttle plate (carburettor or injection) pulls constant vacuum on crankcase void to keep it "empty" in effect. But as noted, if that supply is too great it or shifting, it can affect idle rpm hence the dipstick has a seal at the top to prevent it sucking in through there.
One of the checks is to pull the dipstick on this, revs should go up, then by pulled back down to target as ecu modulates the air bypass route to adjust.
It fails if pipes/flame traps etc are not maintained and flow impaired.
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The A series positive crankcase system consisted of a spring loaded valve with a rubber diaphragm inside this was connected directly to the inlet manifold iirc. The other side of the valve was connected by a pipe pipe to one of the two crank case side covers with a simple tubular oil separator type device combined with the cover. My understanding is it was introduced to meet emission regs back in the day - effectively any vented gas from the engine was recycled into the combustion system. If you undid the oil filler cap the engine revs would drop & it would often stall.
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That's likely a side effect of SU type carb in that the slide is vacuum operated which also controls fuelling, drop in vacuum and carb slide should go down, even though traditional air leak on engine side ordinarily results in increasing revs.
So conflicting outcome based on equipment peculiarities. The carb damping oil will stop flutter and control rate of change, but will ultimately settle to where vacuum dictates.
I used oil viscosity here to trim fuel "mapping" profile in setting them up, the SU type that is.