I have completely overhauled my brake system:
New lines
Rebuilt calipers
Rebuilt MC

Is Silicone fluid the way to go since it does not absorb moisture? I would like to avoid bleeding the brakes every 2 years just to prevent corrosion in the system.

Does anybody have a strong opinion on which is the best way to go?

Thanks
Rob

QUOTE (514727625 @ Apr 5 2006, 06:57 AM)

I have completely overhauled my brake system: New lines Rebuilt calipers Rebuilt MC Is Silicone fluid the way to go since it does not absorb moisture? I would like to avoid bleeding the brakes every 2 years just to prevent corrosion in the system. Does anybody have a strong opinion on which is the best way to go? Thanks Rob

thats the reason my brake pistons have corrosion on them.

b

I dug into this a couple of years ago

General consensus was that even thoug "theoretically" the silicone DOT5 has better properties (non hygroscopic) in the real world people who tried it had trouble getting a firm pedal

Because of this, I didn't try it and went regular DOT4

Maybe others here have tried it?

Seals in the system need to be designed for DOT 5
our "old bugger" systems are not. in fact I am not even aware of any cars that use DOT5. However most Motorcycles do use DOT5

I just use CASTOL LMA DOT4 works good and I do a bleed once every couple of months because I do drive the piss out of my car.

I use ATE super blue. It's supposed to be good for high heat situations and it is a pretty blue color!

QUOTE (Jaiden @ Apr 5 2006, 07:24 AM)

I use ATE super blue. It's supposed to be good for high heat situations and it is a pretty blue color!

thats a special order item isnt it?

b

I ordered it from Pelican. Like 20 bucks for a liter and you'll need more than one.

I haven't driven the car yet with the new brakes but I'll let you know how it feels

I think it depends on the use of the car. For a car that is not driven on the track and sits undriven for periods, DOT5 is very good.

I have used DOT5 (Silicone) fluid in my MG brakes for about 15 years. As long as you don't shake up the fluid or do anything else to get air entrained in it, getting a firm pedal has never been a problem. I have never had any problems of any kind with the fluid. I only bleed the brakes when some other service needed (several years) and the fluid is always clean and clear with no rust or debris.

That being said, I have ATE gold in my 914 because I hope to do some DE's or time trials with it at some point and will be flushing the fluid regularly.

At lot of British car guys swear by the Castrol LMA. Sort of a compromise solution.

I normaly use ate blue.

I do have a odd question though because you guys got me thinking.....oh no not that!

With the 23mm master cylinder the cars pedal is hard as hell. It's running ate also. So what I am wondering could something like a dot5 give you back some pedal feel? Sorry not trying to hijack the thread but I would like to know if this is something that would work and if it is even a good idea.

QUOTE (turboman808 @ Apr 5 2006, 06:41 AM)

I normaly use ate blue. I do have a odd question though because you guys got me thinking.....oh no not that! With the 23mm master cylinder the cars pedal is hard as hell. It's running ate also. So what I am wondering could something like a dot5 give you back some pedal feel? Sorry not trying to hijack the thread but I would like to know if this is something that would work and if it is even a good idea.

The pedal feel with the 23mm MC is more mechanical advantage being taken away then the fluid. Do you have upgraded calipers? The larger MC with the stock calipers makes the pedal movement far less than stock and a lot harder pedal feel. I don't think different fluid will make much of a difference.

My '81 Honda Goldwing and '72 VW Squareback are filled with DOT5 and not a single problem braking with either vehicle.

I have used DOT-5 Silicone for about 18 years in my 914. Never a problem on the street or the track. I buy a no name fluid at the local FLAPS. I bleed the brakes before every event. I am used a 19MM master cyl. and pedal feel was great. Stock front and real calipers with a lever prop. valve.

Since I have converted toe car to a six. I have changed to larger calipers ( Wilwood front and M Rear) and I am in the process of up grading the master cyl. to a 23. My ffiend has this set up on his GT-5 PCA 914 so I know it works.

van914

so I assume one would have to completly drain the car of brake fluid to change from DOT3 to DOT5?

b

QUOTE (bd1308 @ Apr 6 2006, 04:41 AM)

so I assume one would have to completly drain the car of brake fluid to change from DOT3 to DOT5? b

I didn't. Just bleed the system as if you were doing a standard fluid change. You'll see the DOT5 fluid as it's purple in color.

It all depends on how big you go and how good the Doctor is. You can get saline too.

My understanding is that you should completely clean out the brake system and replace all rubber parts. I have read that the reason that the fluid types are incompatible is that, while conventional fluid naturally swells the rubber seals, silicone has seal swell additives to accomplish this. If you get conventional fluid plus the additives, bad things happen to the seals.

I guess Air_Cooled_Nut's experience suggests this not always the case.

Every brake system I've pulled apart that had DOT5 and non-DOT5 brake fluid mixed was full of a white goo. This stuff was very difficult to clean out, and blocked some of the smaller passages in the system.

However, none of the DOT5 fluid I've seen was purple, so maybe there's a fluid out there that won't turn into white goo on contact with mineral-based brake fluids.

The Brit-car guys LOVE DOT5, mostly because their cars spend most of their time sitting. It's claimed DOT5 will keep out water, and thus will prevent rust. Others argue that because the DOT5 doesn't absorb the water in the system, that it PROMOTES rust.

Motorcycle guys, for the most part, HATE DOT5, and won't go anywhere near it.

I don't have a strong opinion on it, but it does seem to polarize people. I use Castrol LMA, as it's easy to get and cheap.

I've never heard of using DOT5 for anything other than cars that are stationary displays like the typical British cars...

IMO the hygroscopic nature of DOT 3, 4 brakefluids is an feature not a bug. Your brake system can get moisture in it either through condensation, rain, or washing (unless you've got one of those stationary display cars).

If your brake fluid doesn't absorb H2O, the H2O in the system will eventually find it's way to the worst imaginable location (according to Murphy) and play heck with the brake system (rust or worse).

Of course acknowledging the specific examples cited here you can get away with almost anything for a while...

I use Castrol LMA and am pretty content.

Good luck,
Kevin

Install SpeedBleeders. It makes it easy to flush your brake system more than every two years.

QUOTE (lapuwali @ Apr 6 2006, 08:27 PM)

...Motorcycle guys, for the most part, HATE DOT5, and won't go anywhere near it...

Do you know why? The fact that it doesn't eat paint gives it a thumbs-up from me.

As to the white goo, yes, I've heard that as well. If true it doesn't appear to be affecting my braking performance (street use only). Then again, maybe there aren't any really small ports in old VW's and Goldwings

I used Dot 5 on a 911 I owned years ago.. It was purple colored, and I had that fluid in that car for awhile..I never noticed the spongy brake pedal that was rumoured when using DOT 5.

Also Im sure most of you do this.. but when you do a fluid change on your brakes, you evacuate the MC with a turkey baster or something, rather tahn pump all that fluid thourgh the system.

Since I started racing many years ago.. brake maintenance has become paramount.. and brake fluid gets flushed before every event, and sometimes before each session..

Do you guys know why the fluids are different colors?!?!?!?!

It's so that you'll know when the system is completely flushed when you want to flush it. That's pretty much all. Keep bleeding until the gold runs out and the blue takes over. Or vice versa. Or green and purple (or whatever) for DOT5.

SO... don't mix two different colors. That's a drag.