Silicone DOT 5 Brake/clutch fluid.

[PodOne]

The braking and clutch systems are both completely new with all pipes, MC's, calipers etc replaced. So while it's free of contamination I have decided to go with Silicone fluid.

Question to those who have gone down the same path how much fluid is required and which one would you recommend?

Any tips regarding its use.

Thanks

Andy

[Tim D.]

I'd get a litre of the automec  stuff. I think it is all much of a muchness. 

Tim

Edited September 3, 2022 by Tim D.
Autocorrect error

[harrytr5]

Automec is what Tim is referring too. Moss does silicon brake fluid in half litres but agree with Tim, 1 litre.

Regards Harry

[boxofbits]

Hi Andy

 There has been lots of discussion on here in the past about Dot5 silicone fluid, and opinion is much divided.

However, having used it, and from personal experience I felt it gave a spongy ‘ imprecise’ pedal, and not wholly certain it is a good choice. It is not hygroscopic apparently, but that doesn’t mean it’s good.

I use Dot4, it gives a firmer pedal and my advice would be to stick to Dot4, but personal choice.

Kevin

[stuart]

Im not a fan of it but FWIW the Moss Dynolite version is cheaper than Automec. 1ltr is about right to give you some "just in case" spare and when bleeding do it very slowly as it froths easily.

Stuart.

[Tim D.]

17 hours ago, PodOne said:

The braking and clutch systems are both completely new with all pipes, MC's, calipers etc replaced. So while it's free of contamination I have decided to go with Silicone fluid.

Question to those who have gone down the same path how much fluid is required and which one would you recommend?

Any tips regarding its use.

Thanks

Andy

This is a bit of a can of worms in terms of dot5 or dot4.

I'm a fan and have run it in a number of old cars for many years with no issues. But others have struggled. Not had the spongy pedal feel and have done track days and alpine rallies with no issues. 

Each to their own. But starting with a new refurbishment hydraulic system is definitely a good way to begin. 

Tim 

[john.r.davies]

Or, of course, just to confuse the situation, you could use DoT 5.1, which is not silicone, but has a much higher rating than DoT4

[monty]

I have used it for over 16 years with no real problems. Pedal is probably a little more spongy than when using ordinary fluid but a big plus for me is that it has not leaked all over the vulnerable paint area near the master cylinder location. I have pristine paint there!

[monty]

Talking of silicone fluid, what is the recommended replacement time or can it in theory stay unchanged forever?

[Tim D.]

49 minutes ago, monty said:

Talking of silicone fluid, what is the recommended replacement time or can it in theory stay unchanged forever?

I know it is used for long term storage of US army vehicles because it can vekeft in situ for some time. In theory it can accumulated water which will sink to the lowest point which can be the calipers. If this boils during operation there is in theory and issue. But not heard of it actually happening. I'd have said changing it when you change  the flexi hoses is probably reasonable. 

Tim

[RogerH]

All brake fluid systems will take in water.

There is a very small  vent hole in the cap.  Atmospheric pressure changes continually and that is what causes the damage.

DOT 3/4 &5.1 adsorbs the water in the M/C and the pumping action eventually sends it around the system

Dot 5 absorbs water and like above is sent very slowly through the system.

The difference is that DOT 5 has actual free water resting on the surface - if this surface is steel it will rust

DOT 3/4 &5.1 will have less water resting on any surface because the majority of it is in molecular combination with the brake fluid.

You pays  your money and you takes you chance

 

Roger

[harlequin]

Like many I have used silicon fluid for donkeys years without problems.

Just one tip though, keep a litre in the boot when on a trip because if you need to top up its unlikely garages will have any on the shelf. If you do have trouble Harley Davison dealers carry stock as it used by Harleys from the factory but its very expensive.

George 

[Z320]

I‘m with Roger!

The moisture cannot be stopped going through rubber, seals, plastic and the ventilation hole because of the difference of concentration.

This is also the case if the brake liquid cannot absorb moisture.

The busy cleaning mate DOT4 (or 3, 5.1) collects the water - and is fired (by some guys),

while the lazy bugger DOT5 does nothing and gets the best reference.

This is why I use not DOT5

Edited September 4, 2022 by Z320

[PodOne]

A real can of worms then with respected formites on both sides of the fence!

Should I flip a coin?

Silicone better for a braking system which will inevitably see a period of near non use during the salt spreading season but still absorb water albeit in a different manner and slower rate. Is it worth the added cost given the brake system is bound to require attention for one reason or another and bleeding anyway (I'm always negative!)

DOT4-5.1 all absorb water and are all relatively cheap, readily available here and abroad but require periodic biannual replacement. Should this be viewed as a painful chore or simply the opportunity to get personal with the braking system and suspension components and undertake some preventative maintenance? 

Not too sure now?

Better review the situation as the last song goes in Oliver. 

Andy

[stuart]

1 minute ago, PodOne said:

A real can of worms then with respected formites on both sides of the fence!

Should I flip a coin?

Silicone better for a braking system which will inevitably see a period of near non use during the salt spreading season but still absorb water albeit in a different manner and slower rate. Is it worth the added cost given the brake system is bound to require attention for one reason or another and bleeding anyway (I'm always negative!)

DOT4-5.1 all absorb water and are all relatively cheap, readily available here and abroad but require periodic biannual replacement. Should this be viewed as a painful chore or simply the opportunity to get personal with the braking system and suspension components and undertake some preventative maintenance? 

Not too sure now?

Better review the situation as the last song goes in Oliver. 

Andy

If you have your modern serviced at a main agents they insist that the brake fluid is changed every three years anyway. No moderns use Silicon though thats more to do with ABS systems. Above mention of its use for long term storage of US military vehicles is correct and thats what its best for. Your choice your car.

Stuart.

[RogerH]

Hi Andy,

simply the question comes down to convenience & annoyance.

DOT 5 is the poorer relation regarding brake fluid BUT it does not remove the paint under the M/C. This is a valid concern.

DOT 3, 4 & 5.1 is the better fluid AND high quality is out there  ATE200 etc

If you can protect the underside of the brake M/C with a drip tray then you have your answer.

 

Roger

[Z320]

Surfaces which had contact with silicon are difficult to paint and to re-paint.

This is why the war industry worries  and avoids the use of any silicon anywhere on their cars.

A friend of mine owns a company, he zinc coats steel for the car industry.

What for should he use silicon? Anyway he has to confirm all producers the parts are 100 silicone free…

Edited September 4, 2022 by Z320

[Waldi]

Hi Andy,

I would not use dot 5 … just kidding, I use it too.

I bought two (1 litre) bottles Dynolite from Moss, one spare. I filled my system around 4 years ago, and one bottle was sufficient, including the bleeding.

Compatibility of this fluid with the rubber materials in hoses, seals etc. was confirmed by the suppliers that I contacted (Past Parts and Moss) who had supplied my brake components.

Last month my PDWA valve developed a leaking O-ring; I think I overlooked a light scratch in the bore during the rebuild which damaged one O-ring. I was glad I had filled the system with Dot 5! The O-rings came out ok when I replaced them, they had not swollen or become brittle.

Small tip:
Poor the fluid gently in the reservoir to minimise small air bubbles getting entrained.

Waldi

[AndyR100]

I use Dynalite from Moss which is cheaper than Automec, even more so when they have an offer on  

……… Andy 

[Tim D.]

Been on forums for more than 20 years for a number of cars and I have an observation. 

When something is a "can of worms" it is usually because neither option has a clear advantage on all points. In this case the best route is to flip a coin or just make a choice. 

Cheers 

Tim (silicone in the brakes and oil in my triunions)

[PodOne]

Thanks all for the feedback and debate.

On balance I think an about face is in order for me at least.

DOT 5 and a drip tray.

The only source I know of these is from Australia or make your own.

Andy

 

 

[r-fox]

DOT 5.1 shows a higher boiling temperature than DOT4 when fresh.

An advantage under racing conditions.

BUT it absorbs moisture quicker so it needs to be changed in shorter periods of time which is not dramatic hence it's usual to check/renew the brakefluid of racecars more frequently anyway.

While water affiliates into a true solution with DOT3 - 4 - 5.1  it will stay separated from silicon fluid ( DOT5  ).

As a matter of theory the accumulated water tends due to its higher density  sinking to the deepest point of the brakeline which is obviously the bleed srew . Thus easily getting rid of it while bleeding .

At the main restauration of my TR4 by the previous owner the brake system got filled with DOT5 of Harley Davidson , that was 1990 .

After 2000 braking with Dynalite ,  done quite a number of longdistance rallying, no issues what so ever.

 

Wolfgang

[RogerH]

Hi Wolfgang,

The bleed screw is at the high point of an enclosed chamber/area (pistons)

Water will accumulate at the bottom on the chamber /area (pistons)

Roger

[Andy Moltu]

The solution to that is to bleed the brakes after a series of heavy braking from speed to get any fluid hot and when you bleed the steam will rise to the top and be bled out of the callipers.

[stuart]

13 hours ago, Andy Moltu said:

The solution to that is to bleed the brakes after a series of heavy braking from speed to get any fluid hot and when you bleed the steam will rise to the top and be bled out of the callipers.

You think? Thats never going to happen.

Stuart.