Dot 5 Silicon Brake Fluid

[PIC]

Hi, I've contacted my local Porsche dealer with regards to using Dot 5 brake fluid in my 996 C4. DOT5 is silicon based. Silicon doesn't absorb water. It is used in racing vehicles and other high performance applications. The Porsche Centre have not recommended this and informed me they use only Dot 4. <_< Are Porsches not High Performance Vehicles, or do the centres just want to keep us coming back ?Have any of you used Dot 5 and what are your views on it ? If so have you any Dot 5 recommendations.

Many thanks

[kam]

I heard that the silicon based fluid is very hard to bleed.

[PorschePRH]

You will find loads of people that will tell you that Dot 4 and Dot 5 systems are not compatible. So according to them, whatever you start with, you have to continue with. They will tell you that the seals will be ruined with the switching, and that unless you drain and flush every little bit of the other fluid you will have problems.

In the end, it's not worth messing with because it's not the end of the world to do a quick brake bleed every couple of years. Fluid changes are the nicest thing you can do for your car. And if you race your car, there are plenty of hi-perf Dot 4 fluids that have very high boiling points.

[ar38070]

Use DOT4.

DOT 3/4 and DOT5 are not compatible. If you change to DOT5 you have to be sure that you completely purge the system.

DOT 3/4 absorb water over time which lowers the boiling point. DOT 5 does not absorb water but you still get water in the system. In either case you have to worry about corrosion and you still have to bleed the brakes. Since DOT5 does not actually absorb the water, the water will tend to collect in various spots in the brake system (system dependent). When you bleed/flush the system the water may or may not be removed. With DOT3/4 as the water is aborbed by the brake fluid, when you bleed/flush you remove the water. The worse case scenario for DOT5 is if the water collects in the caliper. Then of course your fluid will boil at 212 degrees.

DOT 5 may be incompatible with seals in the brake system. Depends on what materials are used in the seals.

DOT 5 used to have higher boiling points. That is no longer the case. There are many DOT4 fluids (sometimes called DOT 5.1) that have similar or higher boiling points.

If you are not tracking your car then I think the point is moot. There is no reason to use a higher quality (more $$$) brake fluid. A lot of us who track our cars regularly just use ATE Blue or Gold (DOT4) and do not have any problems with fluid boiling.

[umn]

Hi, I've contacted my local Porsche dealer with regards to using Dot 5 brake fluid in my 996 C4. DOT5 is silicon based. Silicon doesn't absorb water. It is used in racing vehicles and other high performance applications.

Ok, this is slightly confusing:

DOT 5.0 is a silicone based fluid which is NOT used in racing vehicles. It is incompatible with normal braking systems and you can NOT use it.

DOT 5.1 is similar in properties to DOT 4.0 and it is sometimes used in racing vehicles. It is NOT silicone based, it is COMPATIBLE with DOT 4.0 and INCOMPATIBLE with DOT 5.0

So DOT 4.0 and DOT 5.1 are compatible. The main difference between DOT 4.0 and DOT 5.1 is the higher boiling point and a different viscosity of DOT 5.1, which is necessary in some ABS systems.

Your car does not need the lower viscosity of DOT 5.1 but the higher boiling point is useful. I would therefore use a DOT 4.0 fluid with increased boiling point, such as ATE Racing Blue or ATE Typ 200 (same fluid, just one is blue and one gold in colour).

Cheers,

Uwe

Edited April 12, 2005 by umn

[plima]

When Silicone (not silicon!) brake fluids first became available in the 1970s I "upgraded" my 911 to silicone. At Dow-Cornings recommendation, I replaced all the caliper seals and rebuilt the master cylinder and washed all the brake lines with ethanol. Silicones are very attractive for this application since the are not harmful to paint, are not hydroscopic, and have very high boiling points. HOWEVER, it is a BIG mistake for a car that is driven hard on the street or track. After bleeding the system countless times (over 1 year I used 2.5 GALLONS) using various techniques recommend by D-C and invented myself, the pedal was never as firm as the first pass bleed with a DOT-4 glycol based fluid. At this point, I would recommend DOT-5 (Silicone) fluids only for a show car (minimal road time and no track time). It will last forever and preserve your brake system, and it will stop the car, but you'll never get a rock hard pedal and the modulation that comes with it.

As mentioned above, DOT 5.1 are not Silicone fluids, but they do meet the (awesome) high boiling points of Siicone DOT 5 fluids. They are completely compatible with the DOT-4 fluids that Porsche recommends. With careful, regular bleeding and great care not to get on your paint, DOT-4 and DOT 5.1 fluids are the right choice for our Porsches.

[PorschePRH]

Oh, yea, in addition to what I first said you will hear from "others," and you did (I think they touch on all my original points), you will also hear that silicon is compressible unlike standard brake fluid so you will always have a more spongy pedal no matter how good of a job you do bleeding the brakes with silicon....

Bottom line: Just change your fluid regularly with Dot 4 and give Porsche a break (pun!) on this one since there are plenty of other things to hit them about.

Edited April 13, 2005 by PorschePRH

[PIC]

:cheers: Thank you all for your time and advice, much appreciated.

[Bostonduce]

Here you go courtesy of the S2K website:

ARRANGED BY DRY BOILING POINT:

DRY:401F -- WET:284F --- DOT3 MINIMUM (GLYCOL BASE)

DRY:446F -- WET:311F --- DOT4 MINIMUM (GLYCOL BASE)

DRY:500F -- WET:356F --- DOT5 MINIMUM (SILICONE BASE)

DRY:500F -- WET:356F --- DOT5.1 MINIMUM (GLYCOL BASE)

DRY:527F -- WET:302F --- AP RACING 551 ($12.95/0.5L OR 16.9 OZ)

DRY:527F -- WET:347F --- VALVOLINE SYNPOWER DOT3 & DOT4

DRY:536F -- WET:392F --- ATE SUPERBLUE/TYP200 ($9.95/1L)

DRY:550F -- WET:284F --- FORD HEAVY DUTY DOT 3 ($4/12 OZ)

DRY:570F -- WET:284F --- WILWOOD 570 ($5.65/12 OZ)

DRY:570F -- WET:284F --- PERFORMANCE Friction Z rated ($6.27/16 OZ)

DRY:590F -- WET:410F --- AP RACING 600 ($16.95/0.5L OR 16.9 OZ)

DRY:590F -- WET:518F --- CASTROL SRF ($69.00/1L 0R 33.8 OZ)

DRY:593F -- WET:420F --- MOTUL RBF600 ($12.95/0.5L OR 16.9 OZ)

DRY:601F -- WET:399F --- BREMBO LCF 600 PLUS ($26.75/0.5L OR 16.9 OZ)

DRY:610F -- WET:421F --- NEO SYNTHETICS SUPER DOT 610 ($11.95/12 OZ)

DRY:610F -- WET:421F --- PROSPEED GS610 ($39.95/16 OZ)

DRY:626F -- WET:417F --- WILWOOD EXP 600 ($16.95/0.5L 16.9 OZ)

ARRANGED BY WET BOILING POINT:

DRY:401F -- WET:284F --- DOT3 MINIMUM

DRY:570F -- WET:284F --- WILWOOD 570

DRY:570F -- WET:284F --- PERFORMANCE Friction Z rated

DRY:550F -- WET:284F --- FORD HEAVY DUTY DOT 3

DRY:527F -- WET:302F --- AP RACING 551

DRY:446F -- WET:311F --- DOT4 MINIMUM

DRY:527F -- WET:347F --- VALVOLINE SYNPOWER DOT3 & DOT4

DRY:500F -- WET:356F --- DOT5.1 MINIMUM (GLYCOL BASE)

DRY:500F -- WET:356F --- DOT5 MINIMUM (SILICONE BASE)

DRY:536F -- WET:392F --- ATE SUPERBLUE/TYP200

DRY:601F -- WET:399F --- BREMBO LCF 600 PLUS

DRY:590F -- WET:410F --- AP RACING 600

DRY:626F -- WET:417F --- WILWOOD EXP 600

DRY:593F -- WET:420F --- MOTUL RBF600

DRY:610F -- WET:421F --- NEO SYNTHETICS SUPER DOT 610

DRY:610F -- WET:421F --- PROSPEED GS610

DRY:590F -- WET:518F --- CASTROL SRF

The military is the biggest user of silicone brake fluid, but they have started to process to go back to traditional brake fluid.

Don't use it in ABS systems! In your '45 Packard it's fine.

Regards

BD