Brake fluid

Steve C

Member
Hello all, advice needed please,
just purchased a p6 2000 tc and when reading through the drivers handbook which got with the car, it states use ( brake and clutch fluid crimson to specification sae j 1703.)
looking in my brakes the fluid is red.
checking the history of the car it had all new seals, front and back, + various pipes etc changed about 8000 miles ago,

i have read that silicone fluid is red in colour, would it be safe to assume my fluid is silicone, and would it be ok to top up with dot 5 silicone?

many thanks
Steve
 
The old handbook specification being Girling Crimson is DoT 3 , but I haven't seen it being easily available for many years. and that certainly wasn't Silicone .
 
so if the fluid is red in colour, how can i find out what it is? could it be silicone? ive never come across red brake fluid before.
 
Hi Steve,

I would say your best bet is to flush the entire system and replace it with a known fluid. Also, remember that specifications change and what was current 50 years ago has long since been superseded. Castrol Dot 4 brake fluid or Nulon Super Dot 4 are both entirely suitable.

Ron
 
Hi Steve,

I would say your best bet is to flush the entire system and replace it with a known fluid. Also, remember that specifications change and what was current 50 years ago has long since been superseded. Castrol Dot 4 brake fluid or Nulon Super Dot 4 are both entirely suitable.

Ron
I’d respectfully disagree. If switching from silicone to dot 3/4 or vis a versa you not only need to flush the system but replace all rubber seals. Better to identify the current fluid and continue using it or replace all seals and thoroughly flush the system with the new fluid.

I’ve seen people try and replace fluids before with out swapping out seals in the past. Seals fail pretty rapidly if not swapped out.
 
thanks to all three, i think i will go down to our local brake specialists and see if they can identify it, and then decide the best course of action.

regards Steve
 
I’d respectfully disagree. If switching from silicone to dot 3/4 or vis a versa you not only need to flush the system but replace all rubber seals. Better to identify the current fluid and continue using it or replace all seals and thoroughly flush the system with the new fluid.

I’ve seen people try and replace fluids before with out swapping out seals in the past. Seals fail pretty rapidly if not swapped out.

You make a good point. I have never used silicone nor had to change seals after changing fluid. Mineral brake fluid I have only ever used.

In the case of a road-driven P6, what benefit does silicone brake fluid deliver? I am assuming it is not hygroscopic hence longevity and corrosion resistance are improved. Mind you, with stainless steel sleeves and pistons, corrosion is of very little concern.

Ron
 
In my time working on cars, I have seen both red and clear brake fluids, in tins bought from motor factors, so I would not trust the colour.
I would not expect any professional working on brakes to change to Silicone without identifying the fact, but too much of a risk to trust this.
My understanding is that the 2 types will not mix, so if you need to top up your system, you really do need to know what type o fluid your have.
I have been told that the advantage of Silicone is tht it is not hygroscopic so over time will not absorb water which will corrode your brake pipes.
Nor will the fluid boil under extreme use. probably not too relevant unless you drive your P6 really hard over mountain passes or on tracks-days.
here must be some drawback or it would be used in every braking system.

it is still recommemded that you change your brake fluid every 3-5 years?
 
I've never had a problem with ordinary standard DOT 4 brake fluid, you still need to replace it every 2years.
At the garage I work at now we use mineral DOT 5.1.
 
If I may deviate from the main theme of this thread for a moment, how long might one reasonably expect braided brake hoses to last? Are they also something that needs to be changed at a specific interval?
 
In using my Cobra replica on track I boiled DOT 4 and had a very long brake pedal at the first corner on my second stint that day, not good for the heart !

Since using Super DOT 4 I have never managed to boil the fluid, it has the highest dry boiling point of the mineral based fluids and is compatible with all the other mineral fluids without needing any flushing or seal changing.
 
If I may deviate from the main theme of this thread for a moment, how long might one reasonably expect braided brake hoses to last? Are they also something that needs to be changed at a specific interval?
Braided lines have hard Teflon linings, as far as I am aware there is no set period for replacement. Obviously damage and severe corrosion of end fittings excepted.
 
Braided lines have hard Teflon linings, as far as I am aware there is no set period for replacement. Obviously damage and severe corrosion of end fittings excepted.
I’ve had them fitted to Beryl for 8 years now. No problems so far.
 
Silicone fluid is said by some to have less lubricity – is less slippery – than normal fluid. There have been reports of brake servos not operating as they should when silicone fluid is used (it was a discussion in the Imp Club, of which I am still a passive member). The old Girling crimson brake fluid was superseded by green fluid (not the same as Citroën's green LHM fluid) in the 1970s. That green fluid is also obsolete, perhaps because of that potential confusion with LHM. All told, I reckon regular modern mineral fluid is the best bet, and change it every two years or so given its hygroscopic nature.
 
Braided lines have hard Teflon linings, as far as I am aware there is no set period for replacement. Obviously damage and severe corrosion of end fittings excepted.
The strength of braided lines is in the braiding, so they must be replace if there is any damage to the outer braiding.
 
Re braided teflon hoses - the braiding is necessary to prevent the teflon ballooning and failing, so damaged braiding is a big no-no. I have such hoses with stainless end fittings on the clubbie (lotus 7 clone), and I was a bit disconcerted by the (to me) higher tightening forces required to get them to stop leaking. Dont be tempted to try to fit ends onto bare teflon tubes - the crimping of these requires fine tolerances to avoid cutting through the tubing.
 
One way to test if it’s DOT 4 vs silicone. Take a drop and test on a painted surface. If it damages the paint it’s DOT 3 or 4. If not, it’s silicon.
 
I used silicon brake fluid in my P6 years ago and all the seals, which were all brand new, swelled up and made the brakes drag. I had to strip everything and repalce the lot. Never again...
 
Re braided teflon hoses - the braiding is necessary to prevent the teflon ballooning and failing, so damaged braiding is a big no-no. I have such hoses with stainless end fittings on the clubbie (lotus 7 clone), and I was a bit disconcerted by the (to me) higher tightening forces required to get them to stop leaking. Dont be tempted to try to fit ends onto bare teflon tubes - the crimping of these requires fine tolerances to avoid cutting through the tubing.

That depends on the style of fitting you're trying to fit. I've made up dozens of lines, albeit not for brakes, using Aeroquip-style reuseable fitting and have never had a failure. You do have to follow the procedure carefully though, in particular getting the line cut square and the braiding not frayed.

Yours
Vern
 
Back
Top