brake cylinder bleed nipples

Guys, it's a feature, not a problem.

Silicone fluid is not hygroscopic hence it will not mix with water. Which means any droplet lost in the system will stay separate from the fluid. This may not be a problem in our climate, but if you expect freezing temperatures, the droplet will freeze and block your line, hence you will have no brakes.

If on the contrary, temperatures get too hot, the water will boil, and the vapour will behave, err, like the gas it is and compress under pressure, hence you will once again have no brakes.

Which is bad.
 
schlitzaugen said:
Guys, it's a feature, not a problem.

Silicone fluid is not hygroscopic hence it will not mix with water. Which means any droplet lost in the system will stay separate from the fluid. This may not be a problem in our climate, but if you expect freezing temperatures, the droplet will freeze and block your line, hence you will have no brakes.

If on the contrary, temperatures get too hot, the water will boil, and the vapour will behave, err, like the gas it is and compress under pressure, hence you will once again have no brakes.

Which is bad.
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Correct re water of course. Gee, you'd have to try hard to get that much water into the system though. I've read this old argument about silicone brake fluid before (and the dubious one about it being more compressible) and neither are problems if you do things properly. I don't think it is allowed for competition though, and that might be a boiling point issue, or a risk if spilled on the track.
 
JohnW said:
Beware though. Silicone fluid is Dot 5.0. There is also Dot 5.1 and it is NOT silicone, despite young blokes in brake specialist places saying it is the same. Just read the label.
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CORRECT!
What a stupid way of labelling products that are totally different.
DOT 5.1 in the main is DOT 4 upgraded with higher boiling point & not needed in the type of vehicles we use & maintain.
Most arguments against DOT 5 silicone are BS except the aeration when filling & don't pump bleed just vacuum or gravity bleed.
 
RINGER said:
CORRECT!
What a stupid way of labelling products that are totally different.
DOT 5.1 in the main is DOT 4 upgraded with higher boiling point & not needed in the type of vehicles we use & maintain.
Most arguments against DOT 5 silicone are BS except the aeration when filling & don't pump bleed just vacuum or gravity bleed.
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Spot on re bleeding! I vacuum bleed with heavy silicone grease to seal the nipple threads.

I've even heard young counter blokes in one of the local brake specialists telling customers that Dot 5.1 is silicone. At risk of trouble, I stepped in and explained..... It's one of the stupidest bits of classicification/labelling I've seen.
 
JohnW said:
Correct re water of course. Gee, you'd have to try hard to get that much water into the system though. I've read this old argument about silicone brake fluid before (and the dubious one about it being more compressible) and neither are problems if you do things properly. I don't think it is allowed for competition though, and that might be a boiling point issue, or a risk if spilled on the track.
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Not sure how water gets in, but I imagine the tiniest droplet can freeze in the most inconvenient spot (water doesn't go through the tiniest hole where brake fluid or silicone for that matter would go). Like say between the piston and the bore. What is the clearance there? a few tenths of a millimeter? You don't need a lot of water to form a film in that gap and when it freezes I doubt your piston will move.

There's a German engineer (proper degree engineer mind you) on youtube who drives/restores/maintains his Porsches (and Alfas) and explains why he never uses silicone in his cars. Speaks English. Look up Greasy Fingers.
 
Don't worry about any German, anybody. There are always naysayers trying to get subscribers.
Water isn't getting anywhere unless someone puts it in there. DOT5 Silicone is not hygroscopic all other DOT's are so they absorb atmospheric humidity, through breathing.
The US Army & Air Force have been using silicone in all climates including Alaska! for eons.
I've used in every old vehicle I've owned since the 1990's when in the US ~ Reno [it freezes/snows there in winter] & then back here.

I know folk on Model A & WW2 Jeep Forums that haven't changed silicone fluid in 25 years.
That being said I won't use with hydrovacs [US Army did & does] or ABS systems, for good reason.

Telling what type of brake fluid:


HOW TO :
Building a pressure or vacuum bleeder - there is a section @ the end explaining brake fluids.
Take note of John W's comment "I vacuum bleed with heavy silicone grease to seal the nipple threads."
 
The piston clearance is more like a few hundredths of a millimetre. I do take the point about silicone being non-miscible (although freezing is quite irrelevant for my location) but how on earth you'd get water in there there I cannot conceive. If there were droplets inside a calliper, from the fluid entering (you'd not assemble it wet, would you!) I imagine the droplets would settle behind the piston and how you'd get a water film around it I also can't imagine. Mr GF's videos are very good I'd agree. Maybe there is experience in cold climates with freezing water in silicone fluid? I've not heard any real evidence and Mr Harley Davidson would have a problem as they've used silicone fluid for many years. Similarly Citroen 2CVs use LHM for the brakes and it too is a mineral oil and I think immiscible with water.

I can only say that I have been using silicone brake fluid now for slightly more than 30 years with no problems. For my Renault 4CV, I upgraded the brakes after I guess about 25 years and inside they were like new. No water, no corrosion and I hadn't changed the fluid once. So for our cars, I think the potential problem is theoretical not practical.
 
schlitzaugen said:
Not sure how water gets in, but I imagine the tiniest droplet can freeze in the most inconvenient spot (water doesn't go through the tiniest hole where brake fluid or silicone for that matter would go). Like say between the piston and the bore. What is the clearance there? a few tenths of a millimeter? You don't need a lot of water to form a film in that gap and when it freezes I doubt your piston will move.

There's a German engineer (proper degree engineer mind you) on youtube who drives/restores/maintains his Porsches (and Alfas) and explains why he never uses silicone in his cars. Speaks English. Look up Greasy Fingers.
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Yeah, well if any of the old cars here get driven when the ambient temperature is below zero ..... there is a hell of an emergency happening ..... and possible failure of brakes will be the furthermost thing from our minds :)

we rarely get below zero here. its not snow country :)
 
RINGER said:
Don't worry about any German, anybody. There are always naysayers trying to get subscribers.
Water isn't getting anywhere unless someone puts it in there. DOT5 Silicone is not hygroscopic all other DOT's are so they absorb atmospheric humidity, through breathing.
The US Army & Air Force have been using silicone in all climates including Alaska! for eons.
I've used in every old vehicle I've owned since the 1990's when in the US ~ Reno [it freezes/snows there in winter] & then back here.

I know folk on Model A & WW2 Jeep Forums that haven't changed silicone fluid in 25 years.
That being said I won't use with hydrovacs [US Army did & does] or ABS systems, for good reason.

Telling what type of brake fluid:


HOW TO :
Building a pressure or vacuum bleeder - there is a section @ the end explaining brake fluids.
Take note of John W's comment "I vacuum bleed with heavy silicone grease to seal the nipple threads."
Click to expand...
Yes, very good reasons for not using it with hydrovac systems!! I've read about that. The silicone grease finally solved my "where the hell is the air coming from?" problem, as you'd appreciate and laugh about too!
 
I have a question .... Why aren't we all using silicon in trailer brakes so we don't have the change the damn master cylinders/slaves every few years :confused:
 
DoubleChevron said:
I have a question .... Why aren't we all using silicon in trailer brakes so we don't have the change the damn master cylinders/slaves every few years :confused:
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Good question. Next time you change yours I suggest you change the fluid too. My car trailer uses cables.
 
Any change to Dot 5 requires a full overhaul and all new seals! Trailers over 750 kilos have nearly all gone electric braking these days!
 
Although all new cylinder rubbers may be desirable, a full thorough flush with DOT 5 is usually adequate, in my experience.
 
gerrypro said:
No problem with silicone grease if you clean out the entire system meticulously. Then instead of using LHM try dot 5 silicone brake fluid instead. Do it properly and you will never need to touch the hydraulic circuit again.
PS I have been using it for years! Available at Repco!
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When you say to "clean out the entire system meticulously." Is that because of Red Rubber Grease not being compatable with Silicon Fluid.? is that why you need to clean out the entire system meticulously and not just every last trace of old Dot 4 brake fluid
Do you need special rubbers for silicon fluid , or can you just use the standard rubbers .
 
Rally said:
When you say to "clean out the entire system meticulously." Is that because of Red Rubber Grease not being compatable with Silicon Fluid.? is that why you need to clean out the entire system meticulously and not just every last trace of old Dot 4 brake fluid
Do you need special rubbers for silicon fluid , or can you just use the standard rubbers .
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I wish I could answer that correctly in full! I read that all rubber parts need replacing, so I did the change on each car only when was doing a serious brake overhaul, so yes, no rubber grease, just silicone grease. I used whatever mormal seals and hoses were available and all of them were fine but I've "heard" that isn't always the case - I honestly don't know what material to ask for. I ran meths through the system and let it dry for a few days. I didn't have a compressor in 1990!

For all I know there isn't a compatibility problem at all. For me, the whole point was not having a hygroscopic fluid in the disc callipers (alloy) or behind any seal, as I reckon that is where moisture is gradually absorbed to corrode calliper seal grooves. So it suited me to redo all wheel cylinders/callipers and the master cylinder seals.
 
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