Brake fluid survey - lessons for us all

[Graham Perry]

As part of my job on a large site with a couple of thousand employees I tend to get involved in various safety initiatives as a known 'car nut' and I was recently asked to help organise a summer road safety day. As part of this, a series of tests of peoples brake fluid was made in the staff car park. As we all know brake fluid is Hygroscopic and absorbs moisture. Even though the system is sealed it still accumulates even when the car is standing still and the more moisture in the system then the lower the fluid boiling point. Moisture is reckoned to enter mainly via the flexable brake pipes.

 

What prompted us to do this was that Castrol had done a similar voluntary thing with their own staff and the results were cause for concern, so we thought we would replicate the survey. We borrowed from them a fancy brake fluid tester that takes a sample from the reservoir and then boils it in a few seconds and measures the wet boiling point. This being being indicative of the point just before which vapour lock would have occurred under heavy usage ie when the pedal would move to the floor and the brakes would disappear.

 

Anyway in the end about 70 cars were tested and our statistics more or less exactlty replicated those achieved by Castrol whose test used a larger sample;

 

45% of cars had brake fluid that was a cause for concern or worse

20% of cars had fluid that the automatic tester percieved as dangerous and should be changed immediately.

 

On the worst car we found the fluid boiled at only 110 degrees C, the best were typically newish Cars and that was just about 200 degrees. The test is actually conservative in that it measures the fluid in the reservoir and not at the calliper where the fluid damaging moisture accumulates as this is the lowest point. The other finding was that in general cars with brake fluid that was the worst had either not had the fluid changed to the owners knowledge or had had it changed more than 3 years ago.

 

I guess the message for us seveners is don't neglect your fluid, particularly as a seven tends to be used in more extreme conditions than your average car ie sprints/trackdays and hard blatting . Its not for me to make recommendations, but as a consequence of this knowledge I will now only be using high specification fluid in my car and changing it every couple of years or so. As we know many sevens have a reputation for overheating the standard rear callipers at trackdays so a high temperature fluid would seem to be a pre-requisite for this kind of use.

 

The guy who did the testing also tried some Castrol SRF and AP 600 straight from the pot (both had been opened previously though) to see what the difference was, and both boiled at about 290-300 degrees, which sounds pretty good compared to your average 5.1 fluid which seemed from the tests to be about 200 or so.

 

We thought the survey was worthwhile as it increased peoples awareness of what the local police engineer who attended our event described as, "the silent killer"

 

 

 

 

Edited by - Graham Perry on 13 Aug 2003 14:16:08

[Tight fart]

Seen many a road car, disappear into the gravel after the first few laps of their first track day.

 

SLR for sale (www.ashort.com)

T.F@O.F.

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[jingars]

I had never even considered this as a potential safety issue. It makes for frightening reading.

 

I am about to get the front pads replaced on my wife's car - as it is 3 years old I will also ask them to look at the quality of the brake fluid.

 

Thanks for the education.

[I.Mupferit]

It would be interesting to know how many local garages and service centres are aware of the dangers of old brake fluid.

 

In theory they should be aware but I know of one BMW dealership whom I had to insist changed my own brake fluid after 3 years ❗

Oddly, despite it being in the service schedule and, therefore, added revenue for them they were reluctant to change it saying "That recommendation is just manufacturers overkill............. in reality it is designed for lifetime usage". *eek*

 

It probably just came down to laziness or, more worryingly, total ignorance BUT how many other punters would argue with them when talking to the 'supposed marque experts' 🤔

 

Perhaps it ought to be tested as part of the annual MOT 🤔

 

Brent

 

Zetec

 

[Graham Perry]

Brent, I have thought the same for years, but its only recently that reliable and cheapish (£500 or so ) portable testers that boil the fluid rather than use a light test have been available. All the same I would have thought that was within the budget of your average BMW dealer.

 

Is it Vauxhall who schedule a brake fluid change every two years ?

 

It would be interesting to find out how many seveners have had trouble with their fluid on track days ?

[Blackbirdman]

AP600 and change it every year as part of the winter service!

 

Even three years for a road car is probably a bit long. One of my company cars had a day out at Goodwood just before it was replaced and the brakes went after two laps

 

Matt

 

 

 

Is it a bike? Is it a car? No it's Blackbirdman

[Shaun_E]

Caterham's service schedule includes a brake fluid change at 24,000 miles/2 years (including replacing the flexible brake hoses). I had this done early this year so that car was OK for the track days I would be participating in.

I guess if you do a lot of track miles then every year is probably a very good idea.

Shaun

 

Yellow SL #32

[JAG]

I work for a large automotive supplier of braking systems.

 

We recommend, to the vehicle manufacturer, that the brake fluid is changed every two years. Whether they pass this info onto their service centres and owners (through the owners manual) is up to them.

 

 

 

Justin

 

Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.

[Noel Mclaughlin]

And of course you will use only fluid from an UNOPENED and sealed container . Makes you wonder about the brake specialists who have an opened bottle on the bench usually with no cap on it, or worse still an open 20 litre drum of it. I had an interesting experience many years ago when I fitted disc brakes to a car that had previously used front drum brakes, and the first time I used the brakes in anger the fluid boiled in the lines and vapour locked. The pedal went rockhard, the car glided down the road unabated. You see I had not changed the old fluid which was probably eons old and it was drum brake spec as well. Never again will this happen to me, I change mine every 12 months in sunny Australia.

 

Edited by - Noel Mclaughlin on 14 Aug 2003 10:19:55

[Graham Perry]

What I don't understand though is why more garages don't recommend changing it. In some respects its a cash cow for them , say 1/2 an hour at £50 an hour plus £10 profit on the fluid, sounds like a nice little extra to me. This is the sort of thing that some customers are genuinely pleased that you check

[ruff seven]

I look after a lot of different products, and we change brake fluid every service, we charge £35 plus fluid at £8.60 for a

caterham unless they choose to have srf ect; and only £105. plus fluid for eg 550 maranello.

[jboult]

On the track day front, my last outing convinced me that not only did the pads (and shoes) need replacing, but I also needed to do the fluid at the same time.

 

I spoke to a couple of people there, and the recommendations varied considerably for both pads and fluid (old 1600 X-Flow, no specials mods). What do people think is appropriate/necessary for a road car that does three or four track visits a year?

 

 

[Joe 90]

I talked to my tame Mercedes mechanic and discovered that there is a special section in the service record for brake fluid changes. He will always changes the fluid if there record is suspect. Brake fluid supplied in a container that keeps the air out, just like a wine dispenser, so trade shops don't need stacks of small tins.

 

Starting all over at 40.

[moosetestbestanden]

I learned about this on the NSX board over here some years ago. Seems several fellas ended up in the weeds during track time. Lots of debate followed about the NSX brakes (in fact not the best in the world) but the bottom line was just as this thread states: Change the fluid regularly, particularly if you use your car on the track.

 

CYaLata

 

Chris

[alicat]

Had an interesting debate with a Ford garage a few years back. Booked my Ford maverick in for it's service, which according to the service schedule included a brake fluid change. On picking up the car it clearly had not been done

 

Up on complaining I was told that most people don't have it done as it costs extra

 

I pointed out to them that the service they quoted for, and was booked in for included a brake fluid change and suggested they were not sving money but ripping me off - they changed the fluid *thumbup*

 

Alicat

 

 

[Tight fart]

Noel

I had an interesting experience many years ago when I fitted disc brakes to a car that had previously used front drum brakes, and the first time I used the brakes in anger the fluid boiled in the lines and vapour locked.

 

How did you manage to fit calipers without bleeding the old fluid out or did you re-use the old fluid?

 

SLR for sale (www.ashort.com)

T.F@O.F.

www.griptv.com

[Paul Drawmer]

Was buying AP600 from Demon Tweeks.

Got advised that it was more hygroscopic than lots of other fluids and that it should really not be left in for any time (change every couple of events)

For road use, I was advised that Castrol SRF, although less extreme in the new boiling point, would only need changing every other year.

The message was that basically AP600 sucks in water like no tomorrow, and is unsuitable for mixed road and track use as it will deteriorate very quickly.

 

 

[felix.klauser]

Another overlooked factor is corrosion in the braking system. I know of people who have never had to take their brakes apart in 20 and 30 year old cars but have changed the fluid with regularity. That prevents the seized pistons that seem to occur around the 6 to 8 year mark in many cars. An ounce of prevention...