Brake fluid -which type?

[Dave Meredith]

Not sure which type of fluid I've got in my system. According to Steve Heath's Bible
Dot3,4 and 5.1 are all glycol based, absorb water and will strip paintwork
Dot5 is silicone based and does neither of the above.

Problem is the two types can't be mixed

I've put a few spots of my brake fluid on a test sample of paintwork and no reaction.Looks like it's Dot5. Is there any other test I can do? Does it smell any different?

[adam quantrill]

That's not a good test, paint has changed composition over time, and also the wedge paint seems quite resistant to brake fluid.

I found this:

"To determine if an unknown sample is glycol or silicone fluid, put some in a glass jar. Add water a drop at a time. Glycol fluid will dissolve in water with slight milkiness, but silicone fluid will form two distinct layers, with water on the bottom. Silicone stays clean and clear in a brake system, but old glycol looks rusty after years of use. The purple dye transfers from silicone to glycol fluid if you mix them together."

Looks like a reasonable test.

[matt-man]

How Old is the fluid? If its a couple of years old, flush the lot and start again. Its not a big job, i do mine every year to make sure i dont get any moisture in the system and corode the cylinders etc...

[cantus]

I used Dot 5 for my SEAC last year and the rubber seals in the main break cilinder came out in little pieces into the reservoir....... !!!
I discovered it after a break faillure on the motorway a couple of months age.
I think it is because of the Dot 5 which is too agressive for the seals.
Seals were new !!!
I'm back on Dot4

[rev-erend]

I would only ever use DOT 5.1 - but agree if DOT 5 has been used it will need to be tested..

[Dave Meredith]

Thanks chaps!

I'll put a drop of water with it and see what happens. This feels like O level chemistry!

[tempus]

rev-erend said:

I would only ever use DOT 5.1 - but agree if DOT 5 has been used it will need to be tested..

Dot 5.1 is no more,deceased,dead,but the Dot 4 that has replaced it is better.There are different types of dot 4.Tempus

[rev-erend]

Looks like you are right .. castrol seem to make offerings called SRF and response ..

[tempus]

Yes,sorry for tongue in cheek post,there are two versions of Response ,the one to go for is Super Response.Tempus PS to check water content of older fluid it darkens as it absorbs moisture Golden syrup or honey is a good change point.

[GV]

tempus said:

rev-erend said:

I would only ever use DOT 5.1 - but agree if DOT 5 has been used it will need to be tested..

Dot 5.1 is no more,deceased,dead,but the Dot 4 that has replaced it is better.There are different types of dot 4.Tempus

Halfords still sell 5.1

[TVRleigh_BBWR]

I think 5.0 is no more I sure you can still get dot 5.1
All the race car's are running AP600 fluid.

[tempus]

Halfrauds are selling old stock ,dot 4 (later super)exceeds the properties of dot 5.1 so it is no more,dot 5 is silicone based and a different can of worms.Tempus

[TVRleigh_BBWR]

ok I stand corrected.

[GV]

Is this a serious case of Dot to Dot mumbo jumbo or - let's join up the Dots and see what we get? I thinks it's been agreed that Dot 5 is a no go so we are left with Dot 4 or 5.1. We need a defintive judgement....

[adam quantrill]

Wot about Dot 6? ;^)

[tempus]

There is also Dot4 ESP (Elec. Stability Programme ) but no 5.1 Tempus

[shpub]

Dot 5.1 is simply a minimum specification as is dot 4 and dot 3. The problem is that some Dot 4 fluids are improved and unless you know exactly the spec of the Dot 4 it is very difficult to know whether it reaches the same spec as DOT 5.1 or exceeds it. Dot 5.1 is not a recipe but simply a standard.

As for Dot 5.1 being replaced by super Dot 4 ... not totally convinced where that is coming from as all it is doing is saying that some new products exceed the 5.1 spec. Why they then call them Dot 4 instead of DOT 5.1 or whatever is a strange one.

Unless you know specifically that the Dot 4 fluid has been upgraded, assume it is the minimum DOT 4 spec and go for a Dot 5.1. There are plenty of suppliers that stock the stuff.

http://www.volvoclub.org.uk/faq/BrakeFluidComparis...

http://www.h-e-l.co.uk/HEL_Performance_Motorcycle_...

[TVRleigh_BBWR]

adam quantrill said:

Wot about Dot 6? ;^)

All the guys in the TVR Challenge run dot 6. it does need changing every 3-6 month though.

[tempus]

Shpub,speak to castrol,mobil,or any majors and they will be (hopefully}more imformative than me in explaining why super response meets or exceeds dot 5.1 spec and the spec is no longer used .Tempus

[alex290568]

wot about dot 7