Brake fluid change - every 2 years?
Discussion
It's been almost 2 years since the brake fluid was changed on my GT3, I just wondered on the importance of changing it so frequently?
I know some people see this as just the OPC printing money, is it not more sensible to find out if there is additional water content in the fluid (not sure how I go about this) or just get the fluid changed? Pedal feels good to me.
I know some people see this as just the OPC printing money, is it not more sensible to find out if there is additional water content in the fluid (not sure how I go about this) or just get the fluid changed? Pedal feels good to me.
I don't think it can be fully sealed, if it were there'd be a vaccuum created as the pads wear and the pistons sit further out of the calipers, causing the fluid level to drop.
However, 2 year interval is probably way sooner than needed for road cars - Land Rover recommend 3 years (and their braking systems have a lot of weight to stop) which will still be conservative for safety reasons.
However, 2 year interval is probably way sooner than needed for road cars - Land Rover recommend 3 years (and their braking systems have a lot of weight to stop) which will still be conservative for safety reasons.
If you're going on track soon, it might be prudent to change it now because if it has absorbed water, the boiling point will be lower.
As others have said, for the road, you can probably go longer. The point about this is that when moisture has been absorbed, because it's heavier than the oil, if enough droplets come together to form a drip at the bottom of your piston, the calliper will rust. And a rusty/pitted piston will wear a rubber seal and you might begin to lose fluid. This is what you are looking to prevent by changing regularly, rather than losing any pedal feel or boiling your brakes at the end of a fast straight.
As others have said, for the road, you can probably go longer. The point about this is that when moisture has been absorbed, because it's heavier than the oil, if enough droplets come together to form a drip at the bottom of your piston, the calliper will rust. And a rusty/pitted piston will wear a rubber seal and you might begin to lose fluid. This is what you are looking to prevent by changing regularly, rather than losing any pedal feel or boiling your brakes at the end of a fast straight.
WindyMiller67 said:
If you're going on track soon, it might be prudent to change it now because if it has absorbed water, the boiling point will be lower.
As others have said, for the road, you can probably go longer. The point about this is that when moisture has been absorbed, because it's heavier than the oil, if enough droplets come together to form a drip at the bottom of your piston, the calliper will rust. And a rusty/pitted piston will wear a rubber seal and you might begin to lose fluid. This is what you are looking to prevent by changing regularly, rather than losing any pedal feel or boiling your brakes at the end of a fast straight.
Hydraulic fluid absorbs moisture because it is hygroscopic.As others have said, for the road, you can probably go longer. The point about this is that when moisture has been absorbed, because it's heavier than the oil, if enough droplets come together to form a drip at the bottom of your piston, the calliper will rust. And a rusty/pitted piston will wear a rubber seal and you might begin to lose fluid. This is what you are looking to prevent by changing regularly, rather than losing any pedal feel or boiling your brakes at the end of a fast straight.
The water is not separate from the "oil" at any time, or in droplets, you could say albeit somewhat incorrectly, that it is dissolved in the oil.
It's not normally an oil in any case, except where some cars use mineral oil. If it were an oil, or silicone based, it would not be hygroscopic and would not absorb water from the atmosphere either.
All the rusty pistons whether on drum brakes or clutch slaves that I have ever seen were rusty on the outside of the seal's range of movement i.e. the water must have entered via the weak seal for the piston rod.
mark seeker said:
Oddly the local indie charges £103 and the OPC charges £100.
I'll get it changed next month, the fluid will be pretty much 2 years old to the day and with the weather improving a track day will soon be dialled...
Just make sure that they are really changing all of it.I'll get it changed next month, the fluid will be pretty much 2 years old to the day and with the weather improving a track day will soon be dialled...
I had the fluid changed on a Renault at a dealer a few years ago and they just replaced the oil in the header! Seriously!
mollytherocker said:
Just make sure that they are really changing all of it.
I had the fluid changed on a Renault at a dealer a few years ago and they just replaced the oil in the header! Seriously!
Worse than that is that the technician probably didn't think he was doing anything wrong... I had the fluid changed on a Renault at a dealer a few years ago and they just replaced the oil in the header! Seriously!
I would spend the extra £3.
On second thoughts I would do it myself and save about £70. (this saving is variable and dependant on whether you use Porsche brake fluid, Castrol's finest, ATE's Blue soup or Halfords worst). Most GT3's just love Castrol SRF - only the best!
And don't forget the clutch shares the same fluid, so if you want the job done properly ask if they are doing the clutch as well....
If you get a sideways look it will be clear that they weren't intending to and some nasty water soaked old fluid was going to be left in your veins, possibly leading to premature rusting of your pistons, callipers and discs, quite possibly the clutch and the thrust bearing, kidney bowls and front wings (the bit about sharing the same fluid was serious).
On second thoughts I would do it myself and save about £70. (this saving is variable and dependant on whether you use Porsche brake fluid, Castrol's finest, ATE's Blue soup or Halfords worst). Most GT3's just love Castrol SRF - only the best!
And don't forget the clutch shares the same fluid, so if you want the job done properly ask if they are doing the clutch as well....
If you get a sideways look it will be clear that they weren't intending to and some nasty water soaked old fluid was going to be left in your veins, possibly leading to premature rusting of your pistons, callipers and discs, quite possibly the clutch and the thrust bearing, kidney bowls and front wings (the bit about sharing the same fluid was serious).
I was discussing this with a friend over the weekend, remarking that my 993 has a recommended change every three years not two and wondering what had changed, other than dealers getting greedier. He told me that in the US there is no longer a recommended change period at all but they test the fluid and only change once the percentage of water exceeds a certain level (I think he said 5%). Anyone know if this is true? Apparently some cars can go ten years in their brake fluid!
Modern Dot5 brake fluids should make for longer life - I think it is due to silicone based being less hygroscopic - but anyway with a performance car like the GT3 it is assumed you will be using the beast as intended and getting the fluid very hot indeed. Older fluid with a slightly higher percentage of water (doesn't need to be much) reduces the boiling point of the fluid quite dramatically.
So if you drive like Miss Daisy you could probably go for years quite safely without changing - take it on track or enjoy a spirited drive and you would possibly find that the miniscule amount of water in that aged fluid boiling and thus your pedal would get very spongy indeed - or worse.
So in other words it depends on your driving style or intended use. And for the sake of a few quid if you DIY or a hundred if you dont it seems sensible with a car like a GT3 to change the fluid at a min of 2 yearly intervals. I change mine every year and do the clutch fluid at the same time.
I got lazy last year and got Matt at Fearnsport to do it during the service.
So if you drive like Miss Daisy you could probably go for years quite safely without changing - take it on track or enjoy a spirited drive and you would possibly find that the miniscule amount of water in that aged fluid boiling and thus your pedal would get very spongy indeed - or worse.
So in other words it depends on your driving style or intended use. And for the sake of a few quid if you DIY or a hundred if you dont it seems sensible with a car like a GT3 to change the fluid at a min of 2 yearly intervals. I change mine every year and do the clutch fluid at the same time.
I got lazy last year and got Matt at Fearnsport to do it during the service.
gfreeman said:
Modern Dot5 brake fluids ...
It's not a question of "modern" Dot 5 has been around a while, but you don't have the option to choose, you have to use the fluid type that your car needs and can not ordinarily change it from the conventional and still mainly used glycol based fluids (Dot 3, 4, 5.1) to a silicone based one like Dot 5, and vice versa.Anyway dot 5 is also supposed to be a no-no in ABS equipped cars so that's even more limiting.
However if you have an older car that uses Dot 3 you can go do Dot 4 and 5.1 if needed they are just "upgraded" versions of the same thing.
996TT02 said:
It's not a question of "modern" Dot 5 has been around a while,
Jeez! - the bloke was asking why fluid changes appear to be getting shorter and not longer....And as you seem to know your stuff I'm surprised you didn't spot that the fluids I mentioned for the GT3 are DOT 4.
mollytherocker said:
Just make sure that they are really changing all of it.
I had the fluid changed on a Renault at a dealer a few years ago and they just replaced the oil in the header! Seriously!
Yes - and get them to flush through both bleed nipples on each caliper too. I've found on my last two Porsches that the OPCs who serviced them before I purchased only used one bleed nipple. Another reason to DIY, as you know it will be done properly!I had the fluid changed on a Renault at a dealer a few years ago and they just replaced the oil in the header! Seriously!
Never changed brake fluid on any of my cars ever. Even drove my Carrera 3.2 for 6 years without changing fluid. Over 40k miles, no problems at all. Convinced all this hydroscopic stuff, just a dealer/brake fluid manufacturer come on. Then did track day and Bedford Autodrome. After 40 mins, brake pedal went straight to the floor, pressure only returning when car had cooled down for an hour. Very lucky it was near lunch time and was one of the last few cars out on track. Now one of the converted.
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