My 2002 Renault Scenic has on the power steering cap "use DOT 4 brake fluid" so I did, then realised it was not the brake reservoir! Should I be concerned? It was just a small topup. Does it have the wrong cap?
On Sunday, May 19, 2019 at 9:07:23 AM UTC-4, Bill Wright wrote:
First time I've heard of using brake fluid in the power steering, but they
are both hydraulic systems. And this is a French car, wouldn't be
surprised if they used wine. Seems it's probably right, unless the
caps are the same for brake and steering and someone mixed them up.
Google claims one is petroleum based, one isn't, and I might damage rubber seals. Ah well, if it's already losing fluid....
The brake cap also says use brake fluid, but it says "use DOT 3 or 4", it's a different cap altogether, different shape with a sensor on it.
I'll assume a small amount won't do too much harm, and in future just use the correct fluid in each, although I don't think you can still get DOT 3 or 4, I just use 5. 5 is better, right?
The devil is in the details... DOT 5 is a silicone based fluid that is
incompatible with 3, 4, and 5.1. Mixing the two results in sludge.
Changing from one to the other requires a complete system flush.
I have 5 in one motorcycle since that's what Harley used in the '90s.
It's viscosity is supposedly more stable and it doesn't damage paint. It
doesn't work in ABS systems. I'm too lazy to change it but it's hard to
find since it never gained popularity. It's purple so it is easily
DOT 5.1 is compatible with 3 and 4.
It's popular with the custom and classic car crowd. The other flavors
are decent paint removers. Also, it doesn't absorb water which can be
helpful if the vehicle isn't driven frequently.
The downside is it does entrain air and can be a bitch to bleed and get
a firm pedal. Also, silicone contamination is a painter's nightmare. It
doesn't take much contamination to cause fisheyes.
So mostly it was a brainstorm that didn't pan out. One of the selling
points is its high boiling point that was supposed to be ideal for
racing applications. The fly in that ointment was if any water got into
the system it would not mix like it will with DOT 4, and the water would
boil at 212. I believe it is completely banned from racing now.
You do have to wonder about that... USB fell into the same shitpile.
There used to be USB 3.0 that became USB 3.1 Gen 1 that now is USB 3.2
Gen 1. USB 3.1 became USB 3.2 Gen 2, and 3.2 became USB 3.2 Gen 2x2.
At least Microsoft saw the trap. .NET CORE is sort of a cross platform
.NET and started at 1.0. It's now up to the 3.0 RC. Meanwhile .NET
Framework started at 1.0 and is up to 4.8.
The next generation will blend CORE and Framework into 5.0 so there
will never be a .NET CORE 4.x.
The brake fluid numbering makes sense when you realise what they are
doing. Each higher number fr DPOT5.1 has a higher boiling point - the
most important "mumber" for brake fluid. 5.0 was almost a total bomb
-so 5.1 was brought out as it's replacement - with virtually the same
Trying to make sense of any numbering system other than binary code in
computers is futile.
It would have made more sense to call it 6. If 5 wasn't rare on the part
store shelves, how many people would have screwed up their brake system
by buying it instead of 5.1? Even going by boiling point 5 is 260 C and
5.1 is 270 C.
For that matter DOT 2 (castor oil) has a higher boiling point than any
DOT 2 Brake Fluid. DOT 2 brake fluid is oil-based, and it isn't widely
used in the automotive industry. It has the lowest wet and dry boiling
points of all the brake fluids. If your vehicle calls for Dot 3, 4, or
5 fluid, you shouldn't add DOT 2 fluid.Oct 23, 2013
DOT2 was a mix of Castor oil and alcohol - with a boiling point of
only 140c wet and 190 dry.( https://en.wikipedia.org/wiki/Brake_fluid
So apart from DOT 5.0, I can always use a higher DOT number? I assume the car doesn't care if the fluid is capable of a higher temperature. Are there no drawbacks to the higher numbers? Corrosiveness etc?
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