Brake fluid change intervals - myth?

That's the key isn't it, the time frame. Most manufacturers specify 2 or

3 years (Honda say 3 years), but I've seen some as early as only 1 year (Vauxhalls).

It's quite possible to have the fluid last 4 or even 5 years, but by this time you could be waiting for the imminent failure. Obviously the manufacturers have to factor liability into the equation and have a reasonable safety margin.

The fact that you haven't had a brake failure as yet is just indicating that your fluid hasn't been contaminated to the point of causing a problem - yet!

Of course you could just wait until the brakes do fail, and then change the fluid. It's all your choice.

The message from Adrian contains these words:

You even been up that long run up the side of Lake Vrynwyn (SP?)? We blew a bottom hose of the wife's Maestro going up there - and had to come back down with no engine braking 'cos I couldn't run the engine - and no vacuum either.

The message from "Brian G" contains these words:

It's a bit scary the first time but once you've done it a few times the brake fade stops bothering you so much. Last time I did it we had very little in the way of brakes left at the bottom. Why on earth a heavy automatic like that didn't have ventilated discs I'll never know.

I lost the brakes on a CX500 once round the back of Wembley Stadium. As I approached a roundabout a windblown placcybag got wrapped round the disc. I can only assume it must have pushed the pads back slightly 'cos first time I grabbed for the brake nothing happened at the front. Second grab worked fine - but only after a serious rush of adrenalin.

The message from Fergus Duncan contains these words:

Absolutely no idea at all. I tend to change mine every few years because at about that time I have to do something to the back brakes and it's a good excuse.

Clearly that would be rather silly . . . I would also not expect a catastrophic brake failure in any case, if it were caused by moisture ingress then the moisture in the calipers (which if it were there would be boiling and causing gas bubbles) would cause a progressively and very slowly increasing problem (bigger and bigger bubbles) . . . under regular harsh use you'll notice it before it's fatal . . . granted once a year down a big hill may be a different scenareo.

So this, for me, begs the question, there people who have near death experiences on steep hills . . . is it because they haven't changed the fluid in 10 years OR is it because they've had air in the calipers all along . . .

In my experience of servicing frequently tracked cars, air in the calipers is the number one cause of brake failure in extreme use . . . not moisture ingress . . .

Fd

A simular thing happened to me after my last front pad change; I always open the bleed nipple to push the pistons back. No problems usually, however I forgot to pump the pedal to bring the pads back into contact with the discs...it takes a couple of good pushes to make contact which is not fun when you are moving at 10mph towards the junction at the end of our road!

I lost my brakes totally once in a Nissan Sunny some 15 yrs ago because the handbrake cable was rusty. The handbrake hadn't released fully, I didn't notice, and the brake got so hot it made either the brake fluid itself or some moisture boil. I doubt it was moisture though as I had changed the brake fluid some 6 months earlier. The wheel was more than a bit hot though, the shoe had white blisters when I fixed it.

Hmmmm, I wonder here. We often get this argument popping up, especially regarding fluids. I don't really think you can compare a constant high performance use against the average use a normal car gets.

The message from "Will Reeve" contains these words:

I've done that more that once!

I wonder too . . . but I don't see how the comparison cannot be valid . . . if anything I'd espect the fluid on tracked cars to have a shorter life than that in lightly used road cars, simply because of the temperatures it reaches . . . there's also no difference between a heavily used car and a lightly used road car w.r.t moisture absorbtion . . . granted it'll show up earlier on track than on road, but given the fluid is in the system for the same length of time, what's different ?

Fd

I'm thinking more on the lines of the heat being in the system longer, and perhaps preventing moisture from entering the system, maybe even causing some evaporation. Much the same thing happens with other oils and fluids as well. This of course may well have the effect of increasing the life of the fluid.

This is only a bit of guesswork, but educated guesswork nonetheless. I could of course be wrong, and certainly using a car on a track is likely to show up a problem with the brake fluid.

Out of interest what kind of preparation do you have for running your car on a track?

lots enough for a seperate thread more tyre pressures, just the right amount of fuel (too much and you get tank slap unless you've had it baffled), cooling down the brakes on your in lap, making sure you have enough oil in the system, enough water, all the stuff you would check for the MOT when it's due, new brake fluid (if you are going on the track for the first time make sure your brakes are tip top, even if they are new, make sure they are properly bedded in as th elast thing you want to do is try to swindle the insurance company by saying you hit a tree on the A43), make sure there is nothing in your car when you are out on the track, absolutly nothing, from bits of paper, to the rear headrests because they obscure your visability when you are trying to park and you leave them in the footwells, no sweets and deffinitly no camera's gaffer taped to the grab handles, plently of tape to tape your lights up (have a little knock and the glass goes onto the track, where it makes holes in expensive rubber), you also need a helmet and make sure oyu have no loose bits of trim and both bumpers are properly fixed in place , along with all your towing points acesible and attatched (if you are sitting onthe track they come and put a big hook round everything to pull you out, don't be a plum and hav your nice new bumper pulled apart because all theywant to do is get you off the track), amongst other things that will be added to the list :)

SNIP make sure there is nothing in your car when you are

They allow you to have loose items in the car? I'm surprised at that, such things become ballistic in a shunt/rollover.

Steve

Hmmm, I suspect once there is moisture in the fluid in the calipers it has nowhere to go no matter how hot it gets . . . in an engine the crankcase ventilation system provides a way for any moisture to evapourate and be vented out of the system . . . sealed brake systems don't have that facility . . . also . . . although the cars are used on track frequently they are also road legal and used throughout the year . . .

Fitted an oil/water intercooler to keep oil temp under control (car specific problem), fitted more track orientated pads which work the same when very hot or stone cold (personal pref), fitted braided steel brake hoses for better pedal feel (personal pref), change the oil/filter every

4K miles or 8 hours on track, use good quality fully synthetic engine oil and fully synthetic brake fluid (engine oil temps are always high so oil does not last long - it gets carbonised on hotspots in the engine), heat wrap the exhaust/manifold to keep the alternator cool(er), fit alternator cool air ducting to keep the alternator cool(er), fit smaller diameter crank pulley to reduce alternator revs (alternators die with a cherry red manifold 3 inches away from the rectifier and 7500rpm rev limit), detailed inspection before each event.

Apart from some car and personal preference changes it's not far off business as usual with more regualr oil changes . . .

Fd

that's why I said "don't" have anything in the car if you have a footwell full of crap they don't even let you past scquteineering

So your braking system is *not* the same as an average road car then?

So you put new brake fluid in before going onto the track?

i do a lot of track days so yes, i tend to change the fluid a bit more regulalry than it's supposed to be done it's just to make sure the older fluid thats in the calipers is renewed after it's had a hammering is all soo yes, i owuld suggest at least bleeding the crap stuff out of the calipers before you headed out onto the track just to give you the peice of mind that you've done it and have got rid of any problems there is nothing like trying to drive on the track with anything in less than tip top condition because the first problems will just pt you out of the day totaly, not the sort of thing you want if you've shelled out a fair few quid to go in the first place is it