Replacing brake fluid.

Apr 18, 2006 15 Replies

I'm about to carry out a full two year service on my Rover 75 diesel. The service requires the brake fluid to be replaced. No problem except for the fact that when I am *replacing* brake fluid (rather than just 'bleeding' the brakes), I never really know how many 'pumps' on the brake pedal to make in order to fully purge the brake pipes of the old fluid. It's not so bad if you are working on an old car and pumping out mucky brown fluid - but on a two year old car the old fluid is usually as clear as the fresh stuff you are putting in. So the question is - how many pumps of the foot brake is necessary to clear all the old fluid out of the pipes to a) the rear brakes and b) the front brakes? Strikes me they ought to sell brake fluid in different colours and then you can be sure that when the fluid being pumped out changes from green to red that you've done the job properly!!



Uno-Hoo!


They do sell brake fluid in different colours. You can get blue stuff from GSF.

Interesting - I'll look out for some!

Uno-Hoo!

Alternatively, there are bleeding kits that you can get which work the opposite way round, i.e suck

the blue stuff i think your find is synthetic fluid used in competition brakes, race cars ect. check what dot rating it has on the reservoir cap or in the hand book, it should be dot 4 or possibly dot 5.

This stuff is either DOT 4 or DOT 5.1 as I was considering using it in the Golf. It's fine for road use.

thats very true, thats why you should always use brake fluid from a sealed container if your not sure on the age of it. we use an air powered one at work that connects to the resevoir and pressurises the braking system to blow it through rather then suck.

But doesn't that just turn the original question into "how long do you have to let it suck for"?

Personally ('cos I've never changed brake fluid on anything complicated which might object), I've always completely emptied the system of old fluid, then filled with fresh.

Is it true that old brake fluid which has absorbed moisture can hasten rusting up of brake cylinders, or is that a myth?

just to add to my last post, ours holds about 3 litres or so of new fluid so you can keep bleeding till your hearts content, it has an alarm to warn of the fluid getting low in the machine so you dont end up letting air into the hydraulic system.

You absolutely don't want Dot 5, that's silicone based fluid & shouldn't be mixed with any other type. Dot 5.1 maybe, but not Dot 5

For normal road use Dot 4 is fine, Dot 5.1 if you want to be picky.

I.

Indeed. It would help if I knew what the total capacity of the braking system was. In general, all the 'instructions' for replacing brake fluid simply state: "keep this up until the fluid emerging into the container is clean and clear". The problem, as I stated initially, is that on a two year old car the stuff already in there is 'clean and clear' !!

Uno-Hoo!

I have a Clugston (spelling) ezi-bleed system. You drop the pressure in a tyre to around 10psi and attach a pipe which goes to a reservoir for the brake fluid that gets pressurised, then a pipe with a cap that goes onto the master cylinder. All you do to bleed the brakes normally is open the bleed nipples at each calliper & wait until you get solid fluid with no air. Never tried it but I would have thought that you could open each bleed & let the air force out the fluid to empty the system & then refill with new oil. It cost around a tenner many years ago & has been one of the best tenners ever spent; only draw back is it doesn't fit ever type of master cylinder; however the leaflet that came with it did say others were available.

There is no distinction between bleeding and replacing brake fluid in the literature I came across.

"Bleeding Brakes FAQ and Step-by-Step Instructions"

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instructions No.11 and No.12. After 6 pumps, check the reservoir.Total number of pumps, about 10. Naturally, you can't resist looking up what the other gadgets are available for this, and his comments (link in the article)!

Sorry...I actually hit send before I'd finished the message.

Lets put it this way, I've never needed to use a whole 1 litre bottle on a completely empty system.

Many thanks for that. Very helpful!

Uno-Hoo!

It would be this one: Gunson Eezibleed Kit. It's for clutches as well.

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PDF has some useful info. Draper also do one but it's very basic (Not confident that it works!):
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