The place for technical discussions about GA and flying.
Forum rules: Technical discussions about GA only, please.
By gustav
#1875161
My brake fluid is red in colour. Can I therefore simply add red brake fluid to top it up, are the two or more different types of red fluid, or can I simply add any brake fluid to top it off?
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By Flyin'Dutch'
FLYER Club Member  FLYER Club Member
#1875168
You can do as you like, but the first question has to be, why has it gone down.

I have never yet had to top brake fluid up in more than 40 years of motoring and I have driven some jalopies in my time.
By johnm
FLYER Club Member  FLYER Club Member
#1875170
Pad wear may cause the level to go down a bit but it should stay within limits and if that is the cause you don't want to top it up as it will be overfull when you replace the pads.
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By Ben Twings
FLYER Club Member  FLYER Club Member
#1875256
The wrong type of fluid will instantly destroy your O-rings and leave you with a big red puddle under your tyres.

Most light aircraft use MIL-PRF-5606H fluid. It's cheap, but only normally available from aviation suppliers (or scrounging from other aircraft owners locally).
If you have a situation where the brakes can get really hot (e.g. wheel fairings and fast heavy landings with lots of braking). It's possible that the standard fluid could flash and burn. If there's any chance of that use the higher flash point alternative like Royco 782.

In an emergency you can use a Dexron 3 transmission fluid from a motor store. That's petroleum based and won't destroy Buna N seals.
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By Rob L
#1875925
CloudHound wrote:Or like me change the seals to allow automotive fluid.

The original poster doesn't say Permit or CofA type.
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By Rob P
#1875933
What's the perceived advantage of using car fluid?

Rob P
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By mick w
FLYER Club Member  FLYER Club Member
#1875942
Rob P wrote:What's the perceived advantage of using car fluid?

Rob P


It freezes when it's cold , preventing noseovers :wink:
By cockney steve
FLYER Club Member  FLYER Club Member
#1875993
Car fluid is hygroscopic (absorbs water moisture) therefore rots from the inside-out and the boiling/freezing point deteriorates with age. oddly enough, citroen, david Brown/case, and huddersfield-mede spin-driers all use lhm/atf which is not good for the brake-trade but good for the consumer.
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By Rob P
#1876004
I'm aware of the downsides of automotive fluid which was why I wondered the reason for @CloudHound going to the trouble of changing all the seals to use a less suitable product.

Rob P
By Shoestring Flyer
#1876006
cockney steve
To be pedantic not all brake fluid is hygroscopic, DOT 5 brake fluid for instance is not hygroscopic however it is car brake fluid and you wouldn't/shouldn't be putting it in an aircraft anyway.
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By kanga
#1876014
ah, but do foxes like the aviation sort ? :roll: :wink:

https://www.bbc.co.uk/news/blogs-the-papers-58852156

".. And the Times highlights an unusual scourge affecting drivers in Horsham in West Sussex.

Foxes thirsty for a sweet-tasting alcoholic component of brake fluid have been apparently severing brake lines in cars to get their fix.

Thirty people in one street have had their cables chewed - costing £60,000 to repair.

One man has secured a tarpaulin to his Volvo to stop the animals..."
By cockney steve
FLYER Club Member  FLYER Club Member
#1876051
put out a bowl of antifreeze(,pref. blue) -without bittering agent,let nature and Darwin take their course. :twisted:
p.s. iirc dot5 is primarily for racing and has a very short life (6 months?) and is silicon-based.