Bleeding brakes

[Tavy]

Hi all, I decided to change my rear pads yesterday and did the drivers side and when I did the passenger rear, I had problems getting the caliper piston back. It was bending a g clamp. I had the cap off and decided that the only way it was going to go back was to release the pressure, so decided to undo the bleed nipple and to my surprise no fluid came out. Anyway got the piston back and put it all back and got my wife to bleed the brake calliper. When my wife pushed down on the brake pedal, no fluid came out.closed the nipple and did the old close and then undo when brake pedal pushed and then close but after several attempts still nothing. So I started the car for 30 seconds and retried and with the engine off and the fluid came out like a tap was on. After a few cycles the fluid stopped again, so again started the car and had a full stream, ie tap open. Never seen fluid flow so fast so have closed the nipple while I had fluid coming out. Is there a specific procedure as I have looked and can't find anything. I had problems with this calliper sizzling before but have never had to bleed them. Thanks for any info. Lee

 

[SteveJB]

There is an electric motor next to brake reservoir for ABS system which gives you the pressure UHU is the resident genius for the 100 series and somewhere in the 100 forum has done a write up for the braking system and seized callipers perhaps a member can point you in the right direction

 

[uHu]

You really need the FSM to service the 100, and a couple of days to study it.
The rear brakes are only fed from the brake booster, not from pumping the pedal. To bleed the rears you just jam the pedal with a stick, leave the ignition on, and bleed away. Make sure to keep the "tank" topped up. For the fronts you have to pump the pedal, but still keep the ign on to keep the booster running. If you have had air in the system, you also have to activate the abs and then bleed again.

Warning for the 100: The braking power relies 98% on the booster. When the booster motor stops (when, not if) you have to push the pedal like an elephant and get that 2 % braking power, on the fronts only. Make sure the hand brake is in top condition - needs annual service, cleaning and lubrication.

 

[Tavy]

Thanks for getting back to me, I have decided to buy new callipers and put new hand brake linings in and pads so will have to rebleed the back brakes again so I really appreciate you getting back to me and giving me advice. Thanks lee

 

[SteveJB]

When you renew the rear handbrake system get in contact with Chris as he has some upgraded dog bones that give a more improved handbrake movement and there is a good write up on how to do this you will have to search through the 100 forum

 

[Ted only one]

make sure you only use dot 3 others will rot the seals in the pump.

 

[uHu]

make sure you only use dot 3 others will rot the seals in the pump.

Absolutely not. The Toyota 5.1 far outperforms any dot3 when it comes to performance, durability and road safety, and is perfectly safe for all Toyota brake parts,

 

[Ted only one]

that's ok you use it and let me know how the works out I will still use dot3 them brake units are very expensive.

 

[BobMurphy]

I've been doing some research into brake fluid and it seems there's not a lot to worry about providing you use the same type of fluid:

DOT3, DOT4 & DOT 5.1 are all Glycol-based.

Glycol is Hygroscopic - is absorbs moisture.

Having water in the fluid lowers its boiling point and increases the risk of brake fade due to vapour lock if the brakes are used hard.

Glycol brake fluid is rated by two boiling point values - 'Dry' (no water) and 'Wet' (with a standard of 3.7% absorbed water).

The difference between DOT3, DOT4 & DOT5.1 is in their boiling points:


Characteristics of common braking fluids[13][12]

	Dry boiling point	Wet boiling point[a]	Viscosity at -40 °C°F	Viscosity at 100 °C (212 °F)	Primary constituent
DOT 2	190 °C (374 °F)	140 °C (284 °F)	?	?	castor oil/alcohol
DOT 3	205 °C (401 °F)	140 °C (284 °F)	≤ 1500 mm2/s	≥ 1.5 mm2/s	glycol ether
DOT 4	230 °C (446 °F)	155 °C (311 °F)	≤ 1800 mm2/s	≥ 1.5 mm2/s	glycol ether/borate ester
DOT 4+	230 °C (446 °F)	155 °C (311 °F)	≤ 750 mm2/s	≥ 1.5 mm2/s	glycol ether/borate ester
LHM+	249 °C (480 °F)	249 °C (480 °F)	≤ 1200 mm2/s[14]	≥ 6.5 mm2/s	mineral oil
DOT 5	260 °C (500 °F)	180 °C (356 °F)	≤ 900 mm2/s	≥ 1.5 mm2/s	silicone
DOT 5.1	260 °C (500 °F)	180 °C (356 °F)	≤ 900 mm2/s	≥ 1.5 mm2/s	glycol ether/borate ester
DOT 5.1 ESP	260 °C (500 °F)	180 °C (356 °F)	≤ 750 mm2/s	≥ 1.5 mm2/s	glycol ether/borate ester

1. ^ "Wet" defined as 3.7% water by volume

​

There are other categories of brake fluid that we don't usually encounter.

The main alternative is DOT5 - this is silicon-based, cannot be mixed with Glycol and is coloured blue/purple to differentiate it from the pale brown/straw Glycol-based fluid.

Silicone is Hydrophobic - it repels water. I'm surprised to see a 'Wet' value in the table above as it won't have any absorbed moisture - though there may be free water in the brake line I suppose.

Glycol fluid should be replaced every 2-3 years. Silicone fluid can be left longer.

Silicone is used where brakes are likely to be very hot - racing cars & bikes - and by the Military who don't change their hydraulic fluid regularly if possible.

One interesting comment (I won't call it a fact) I turned-up is that Silicone fluid is more compressible than Glycol fluid - therefore the brake pedal will feel a little 'spongy' if Silicone fluid is used.

Glycol fluid contains 'Corrosion Inhibitor' to reduce the risk of corrosion in the braking system. No-where did I find anything that said that DOT3, DOT4 or DOT5.1 had different inhibitors and therefore couldn't be mixed.

It appears from what I've read and seen on you-tube vids is that DOT3, DOT4 & DOT5.1 can be mixed.

I'm working on a 2007 Mazda6. The Haynes Manual says use DOT3 fluid. I'll be flushing it through with DOT4 as that's what I use on all the other cars & motorcycles. I don't expect any problems.

Bob.

 

[uHu]

that's ok you use it and let me know how the works out....

Fwiw, I've been using 5.1 on cruisers and fords since 2003. The only scary thing is how good the fluid looks when I bleed it.

 

[Beastrider]

Bob - you are right that DOT 3/4/5.1 are in the same family and are mixable but they have different minimum performance requirements, as per the table you showed.
One of the ways that the boiling points are increased in glycol ether brake fluids is by using borate esters and it is those that can cause seal damage if the rubber seals have not been formulated to resist them. I expect that is what ‘Ted only one’ is referring to. I would be surprised if Toyota hadn’t already sorted that though, but I don’t have any firm knowledge on that.

The reason that the table shows a wet boiling point for DOT 5 is because that is the minimum value required to achieve the DOT 5 standard.
Silicone fluid is not compatible with our vehicles even though it sounds like it has some attractive properties. You may like to read the thread ‘ENV6’. I offered some experience there to explain why hygroscopic fluids are a good choice for brake fluid.

 

[BobMurphy]

From Wikipedia:

Service and maintenance[edit]​

Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic (water absorbing), which means they absorb moisture from the atmosphere under normal humidity levels. Non-hygroscopic fluids (e.g. silicone/DOT 5 and mineral oil based formulations), are hydrophobic, and can maintain an acceptable boiling point over the fluid's service life. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol-based fluid (DOT 3/4/5.1) will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either. A system filled from dry with silicone fluid does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardised on silicone brake fluid since the 1990s. Silicone fluid is used extensively in cold climates, particularly in Russia and Finland.

Brake fluids with different DOT ratings can not always be mixed. DOT 5 should not be mixed with any of the others as mixing of glycol with silicone fluid may cause corrosion because of trapped moisture. DOT 2 should not be mixed with any of the others. DOT 3, DOT 4, and DOT 5.1 are all based on glycol esters and can be mixed, although it is preferable to completely replace existing fluids with fresh to obtain the specified performance.

Brake fluid is toxic[16] and can damage painted surfaces.[17]


DOT 5 brake fluid is not compatible with anti-lock braking systems. DOT 5 fluid can aerate when the anti-lock brake system is activated. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.[7]

Thanks for the comments Beastrider, I'll read your earlier posts. (Thinks - what do you ride? I have two BMW 'GS' and some British Classics ).

Bob.

 

[Beastrider]

Hi Bob - no bikes actually. Although, I am trying to persuade ‘she who must be obeyed’ that I need a classic British bike. Not everyone’s taste but I always liked the Sunbeam S8 - technically quite interesting.

 

[Ted only one]

why not just make life simple use the dot 3 that Toyota put in it. then you don't need to bother with all that bollocks about performance/ outperforms and just drive it. its cheaper in the long run.

 

[BobMurphy]

Because I have DOT4 on the shelf !

Bob.

 

[Ted only one]

look out for the buzz and the ABS light on and no brakes. that's your brake master cylinder damaged.

 

[Beastrider]

Hello Ted - you obviously have a clear view on brake fluid selection. I am interested to know where that comes from. Do you have direct experience of DOT 4 or 5.1 causing problems with the master cylinder/ booster?

 

[BobMurphy]

look out for the buzz and the ABS light on and no brakes. that's your brake master cylinder fucked.

Errrm - actually the buzzer and warning lights come on when you run out of boost pressure, as when the pump motor fails (as mine did when the electrical contacts fractured - presumably through vibration). Robson & Francis Rewinds can sort the pump motors out. I don't think a leaking master cylinder would cause any warning lights, but I could be wrong.

I have had Toyotas since 2008 and have never had a problem with fluid affecting the seals.

Anyway - when all else fails "Read the Instructions" :

Bob.

 

[Towpack]

I've just overhauled the brakes, complete with fluid flush/change and used the Dot4 pictured above. I also used it for a fluid change several years ago. I'm not aware of any brake fluid that rots seals, even Dot5 althought there are caveats to using it, also as mentioned above. I changed the brake fluid from Dot 4 to 5 on a bike back in the 80's and had no issues afterwards but it required flushing the system through a couple of times to make sure none of the old fluid remained. The Dot 5 I bought back then was clear and over twice the price of the "normal" stuff.

 

[Ted only one]

your like small children before they get burnt, you can tell them its hot and it will burn you. then they touch it. well learn the hard way then