Silicone Brake Fluid life, DOT5

[burbguy82]

I have a vehicle with DOT5, silicone brake fluid. Never had one until now. Is there a life of the fluid? I understand mixing is a no no. Fluid in resevoir is clear as glass. Not sure of age. Sure I change or let it roll?

Wonder why all systems dont use DOT5?

 

[LazyDog]

check the moisture/ water level and change it when needed

 

[Rand]

check the moisture/ water level

you cant do that.
Dot 5 doesn't absorb water so any moisture will puddle and cause corrosion but of course there should be much less water since it isnt absorbed.

We really need more info about the vehicle. Since there is absolutely no info given it could be at 2024 or a 2008.

If in doubt I'd give it a flush.

 

[LazyDog]

you cant do that.
Dot 5 doesn't absorb water so any moisture will puddle and cause corrosion but of course there should be much less water since it isnt absorbed.

Thanks for the info, I was not aware the of this

 

[Jetronic]

I have a vehicle with DOT5, silicone brake fluid. Never had one until now. Is there a life of the fluid? I understand mixing is a no no. Fluid in resevoir is clear as glass. Not sure of age. Sure I change or let it roll?

Wonder why all systems dont use DOT5?

dot5 often results in a soft pedal, it's a bit squishy

 

[FowVay]

What on earth are you operating that uses DOT 5? I thought that stuff went out with the Kennedy presidency.

 

[Dave Sherman]

What on earth are you operating that uses DOT 5? I thought that stuff went out with the Kennedy presidency.

Harley-Davidson motorcycles used it, or at least they did at one point. Antique car owners like it because it doesn't attract moisture and corrode the brake systems, and it doesn't destroy the paint if you spring a leak. It works well for vehicles that sit idle for long periods, it was developed for military vehicles originally. It doesn't attract moisture from the air the way DOT 3 does, which is I question the naysayers who insist it still gets water in it.

OP, I've had it in my MG for the brake and clutch since 2003. I had to refill the clutch once when the clutch master cylinder let go (it was the original), but I had overhauled the brake system with new master cylinder, brake lines, and wheel cylinders, but zero problems.

 

[Dave Sherman]

To address the OP's last question, one reason it's not more widely used is it doesn't play nicely with anti-lock brake systems. In fact, the bottles I have caution you NOT to use it in ABS. Seems because it's slightly more compressible, it could be a problem in a feedback control system like ABS where it's rapidly modulating the brakes. I've never noticed the pedal being spongy in the MG. It also doesn't mix with DOT3, which is more readily available. I changed over the MG when it was bone dry.

 

[JavierH19]

Are you sure it's not 5.1? I really dislike that they made it seem like a small incremental and logically compatible sounding upgrade to 5 when it's not. 5.1 is incompatible with 5 but 5.1 can be used in a 3 or 4 system. They should have called it 4.1 cause it's a compatible upgrade over 4 which is a compatible upgrade over 3. Even 6 would have been better as it's less confusing. And what vehicle is this exactly. I don't know of any modern car that uses 5

 

[Jetronic]

Are you sure it's not 5.1? I really dislike that they made it seem like a small incremental and logically compatible sounding upgrade to 5 when it's not. 5.1 is incompatible with 5 but 5.1 can be used in a 3 or 4 system. They should have called it 4.1 cause it's a compatible upgrade over 4 which is a compatible upgrade over 3. Even 6 would have been better as it's less confusing. And what vehicle is this exactly. I don't know of any modern car that uses 5

but we have a 4.1 already... dot 4 low viscosity.

 

[Pew]

What on earth are you operating that uses DOT 5? I thought that stuff went out with the Kennedy presidency.

I think he bought a Humvee?

 

[burbguy82]

I think he bought a Humvee?

CUCV, but yes, a military vehicle.

Funny enough, the military chose to use DOT5 as opposed to 3. I suppose it is the superior boiling point and or the hydrophobic nature of silicone fluids.

 

[97prizm]

I have a vehicle with DOT5, silicone brake fluid. Never had one until now. Is there a life of the fluid? I understand mixing is a no no. Fluid in resevoir is clear as glass. Not sure of age. Sure I change or let it roll?

Wonder why all systems dont use DOT5?

Silicone brake fluid was developed for a military specification hummvees I think. That's where I first heard about vehicles using it. What vehicle do you have that is silicone based? DOT 5.1 is above DOT4. Many people confuse DOT 5 and 5.1. According to articles that I've found in theory silocone based brake fluid doesn't really ever expire. Moisture collects or pools in the system and has to be purged. It also from reading causes the brakes to feel mushy compared to regular brake fluid.

 

[97prizm]

but we have a 4.1 already... dot 4 low viscosity.

They should have called it DOT S for silocone. That way there'd be no confusion.

 

[burbguy82]

Silicone brake fluid was developed for a military specification hummvees I think. That's where I first heard about vehicles using it. What vehicle do you have that is silicone based? DOT 5.1 is above DOT4. Many people confuse DOT 5 and 5.1. According to articles that I've found in theory silocone based brake fluid doesn't really ever expire. Moisture collects or pools in the system and has to be purged. It also from reading causes the brakes to feel mushy compared to regular brake fluid.

My vehicle predates HMMWVs. Yes, it clearly states silicone brake fluid. Would you like a picture? I am not confusing 5.1 with 5. Thanks though for the consideration.

From what I have read, you are right about it lasting "forever".

I do not understand some poster on here with the "squishy feeling. Fluid does not compress.

It is Hydrophobic, which is to say it repels water.

The same truck, as a civilian model uses dot 3 or 4.

Funny thing is the fluid is clear as a bell. Wondering if I am needing to change it. The 1000 page manual I have for the truck, just says "As Required".

 

[KrisZ]

My vehicle predates HMMWVs. Yes, it clearly states silicone brake fluid. Would you like a picture? I am not confusing 5.1 with 5. Thanks though for the consideration.

From what I have read, you are right about it lasting "forever".

I do not understand some poster on here with the "squishy feeling. Fluid does not compress.

It is Hydrophobic, which is to say it repels water.

The same truck, as a civilian model uses dot 3 or 4.

Funny thing is the fluid is clear as a bell. Wondering if I am needing to change it. The 1000 page manual I have for the truck, just says "As Required".

Doesn’t matter the DOT number, if the cap says silicone it cannot be mixed with other brake fluids.

The problem with silicone brake fluid, all of the water will accumulate at the bottom of the system, so there is no way to test it. You need to flush it on regular basis.

 

[burbguy82]

Doesn’t matter the DOT number, if the cap says silicone it cannot be mixed with other brake fluids.

The problem with silicone brake fluid, all of the water will accumulate at the bottom of the system, so there is no way to test it. You need to flush it on regular basis.

this makes sense.

the fluid in the master is clean as a whistle

i do not know if it has ever been changed. stops on a dime though.

 

[KrisZ]

this makes sense.

the fluid in the master is clean as a whistle

i do not know if it has ever been changed. stops on a dime though.

I would change it just to get a baseline. Another positive of silicone brake fluids, it will not damage paint. So you don’t need to worry about spills.
It’s pretty much the main reason vintage cars and motorcycle owner use this type of brake fluid.