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Brake Fluid

Community Veteran
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Registered: 02-08-2007

Brake Fluid

Like others on this forum I have changed brake pads on a range of cars over the years, a couple of days ago I did the same task on my current car and at the same time managed to change the brake fluid for the very first time.
I Have never succeeded with this on any other car I have owned as the bleed valves were far to secure to be removed, yes I tried releasing oil, used the correct spanner and applied heat using a heat gun (not a naked flame) but all these efforts failed. There is only a certain amount of torque you can apply to these things before they actually snap off and leaving you wishing you had never bothered.
Worth mentioning all the cars I have owned were at least 8 years old which may account for the problem.
I Note the workshop manuals suggest brake fluid should be changed after several years but I suspect in every car I have ever had this has never been done and providing there is no air in the system ie spongy brakes then is there any necessity to change it ?
Any comments anyone ?? 
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Community Veteran
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Re: Brake Fluid

Don't get me started lol.
I had to replace an entire caliper last year on a rear brake so it had the extra complexity of the handbrake cable to deal with too. I'd been unable to undo the bleed valve and eventually after trying everything it just snapped off leaving me stumped hence the entire caliper replacement. What I was most frustrated with is the brake pipe itself that joins up to the metal brake pipe. It has like a nut on it but the metal pipe goes through it so you can't use a proper socket on it and are forced to use a small spanner which naturally round the ****ing thing off and leaves you in a bit of a pickle.
Then I had all that winding back crap to worry about too and after all the hassle the bloke at the MOT centre said he'd passed it but he still wasn't happy with it  Sad
I need a new signature... i'm bored of the old one!
Community Veteran
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Re: Brake Fluid

It is possible to get a special spanner with a slot in it to do the job, essential if you have a pipe blocking access of a ring spanner.
Not sure what type of metal bleed screws are made of but it's easy to snap them.
David_W
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Re: Brake Fluid

I replaced the front brake lines on my motorbike (21 year old lines) with modern braided lines (safer, better, so why did my insurance go up because of it?!).  My front brake has 2 discs so naturally has 2 bleeding valves and no matter how much I tried to bleed them the usual method (open valve, pull lever, close valve, release lever, rinse, repeat) I couldn't get any bite, it just wouldn't bleed properly.  In the end I bought a reverse bleeding kit off ebay for a couple of quid, you connect a syringe with brake fluid to the bleed valve and push the fluid up through the system pushing the air out along with it.  Worked a treat but has put me off bleeding my brakes again as just my front and rear took a whole bottle of DOT4!
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Re: Brake Fluid

Quote from: David
Worked a treat but has put me off bleeding my brakes again as just my front and rear took a whole bottle of DOT4!

a small price to pay, for peace of mind, when you need to stop !  Roll eyes
PowerLee
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Re: Brake Fluid

Quote from: gleneagles
It is possible to get a special spanner with a slot in it to do the job

Flare spanner  Wink
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Re: Brake Fluid

Quote from: gleneagles
I Note the workshop manuals suggest brake fluid should be changed after several years but I suspect in every car I have ever had this has never been done and providing there is no air in the system ie spongy brakes then is there any necessity to change it ?
Any comments anyone ??   

The majority of brake fluid absorbs moisture from the atmosphere so it does deteriorate with age (unless stored in a 100% airtight container), it should be replaced every few years for two reasons: Brake fluid with a high enough moisture content will corrode the inside of brake pipes and other braking components and under heavy braking when things get particularly hot (like descending a long, steep hill) moisture can start to 'boil-off' creating small bubbles making the brakes fade just when you need them the most.
Only DOT 5 (Silicone based) brake fluid (but not DOT 5.1) does not absorb moisture but this is less commonly used.
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MJN
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Re: Brake Fluid

Quote from: w23
Only DOT 5 (Silicone based) brake fluid (but not DOT 5.1) does not absorb moisture but this is less commonly used.

...and, just in case someone decides they'll have some of that, it can't be mixed with non-silicone fluid.
MJN
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Re: Brake Fluid

Quote from: gleneagles
I Have never succeeded with this on any other car I have owned as the bleed valves were far to secure to be removed

That's likely because the owners before you never bothered. If you stick to the maintenance schedule then bleed valves should come undone without issue.
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Re: Brake Fluid

Quote from: MJN
...and, just in case someone decides they'll have some of that, it can't be mixed with non-silicone fluid.

Always use ONLY the correct (or approved) brake fluid for the particular vehicle.
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Opinions expressed in forum posts are those of the poster, others may have different views.
MJN
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Re: Brake Fluid

With the exception of DOT5.1, higher rating fluids can be used in place of lower specifications. Thus, 4 can be used where 3 is specified and 5.1 can be used where 3 or 4 is specified. There will however be little practical advantage in doing so in most cases.