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M's Factory
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Discussion Starter #1
The brake system uses a glycol-based hydraulic fluid, I know here comes the big words, a bit of background reading has been involved. The fluid is "hygroscopic," which means it tends to absorb moisture over time. Moisture lowers the boiling point of the fluid and causes internal corrosion in the brake system. That’s why the fluid should be replaced when brake repairs are made or every two years for preventive maintenance quoted by most manufacturers.

There are several different types, based on the boiling Temperature and other characteristics of the fluid.

DOT 3 or DOT 4 is used in most passenger cars and light trucks. Use only the type of fluid specified by the vehicle manufacturer as recommended in many vehicles service books.

Using DOT 3 in an application that calls for DOT 4 might create a safety hazard.

DOT 5 brake fluid is different from DOT 3 and DOT 4 in that it is silicone-based.

DOT 5 is NOT recommended for any vehicle equipped with antilock brakes - but it can provide long-lasting protection against corrosion for vehicles that are stored for long periods of time or are driven in wet environments.
 

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Sarky

"DOT 5 is NOT recommended for any vehicle equipped with antilock brakes - but it can provide long-lasting protection against corrosion for vehicles that are stored for long periods of time or are driven in wet environments."

Why? and what about DOT 5.1?

Pope
 

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M's Factory
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Discussion Starter #3
You show me a car manufacturer who recommends Dot 5.x ?

I am or have yet to find one, thats not to say its good for its application.

With reference to ABS systems working in cars, I am under the impression it is to do with the fact that most ABS systems are running high pressures. An effective increase/drop as outlined below ;

ANTILOCK BRAKING MODE:
During a brake application the EBCM compares vehicle speed to the program built into it. When it senses a wheel lock-up condition, it operates the anti lock pressure valve to keep the rear wheels from locking up. To do this the EBCM uses a three-step cycle:

Pressure Maintain
Pressure Decrease
Pressure Increase

Changing this from standard fluid with its own properties and Pressure related issues it will change the way the whole system will react.

This is probably why none of the manufactuers recommend changing the fluid DOT level.
 

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ahhh i see.... DOT3 is cheaper

Pope :D
 

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Sarky

I have used in the past, and will in the future Castrol SRF.

This was recommended to me by a freind who works for WSR as they use it in thier touring cars so it must be able to withstand the abuse we could hurl at it ;)

Its a fully synthetic product and more inportantly is a DOT4 and completly non hydroscopic.....
 

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M's Factory
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Discussion Starter #6
im not saying the Dot 5 or Castrol etc are bad, im just saying they are not recommended for cars with ABS etc.

I am personally going to use a Higher Dot fluid in my car, but it will make additional strain on the entire system. I have known of a Skyline GTS to have a Master Cylinder brake away from the main builkhead with Dot5, hence once you upgrade its worth getting some strengthening in there.
 

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M's Factory
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Discussion Starter #7
Also i have to say i dont think the touring cars have ABS and that it is removed and seen as a hinderance, im not 100% sure of that.
 

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Also i have to say i dont think the touring cars have ABS and that it is removed and seen as a hinderance, im not 100% sure of that.
100% correct. ABS actually degrades your braking performance in the dry.

Bloody handy in the wet though.

Although this is all material to me as i dont have ABS:rolleyes:
 

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Hey guys,

Just got my car out the garage and there is a bloody great puddle of fluid in the footwell!!!!

It has been suggested that it is the master cylinder that has gone south, but I have been unable to get it down to my specialist in Maidenhead as it is Sunday.

The clutch seems to be biting higher now and I wanted to top up the fluid so I can get it down there on Monday. It has dropped to about a quater! Which DOT shall I use?? I bought some DOT 4 but don't want to put it in untill I have spoken to you guys.

Would this be ok??

Cheers,

Ian
 
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