Brake Fluid Question [DOT 3] or [DOT 5.1]

Hey Guys,

ive a question.

I want to change my brake fluid and in the GM-Datasheets is written, taht the car need to cange with DOT 3 fluid.

Now my question: The technicans here in germany tells me, that DOT 5.1 is mutch better (its silicon based synthetic brake fluid) but im wondering, because maybe the synthetic fluid will destroy any seals or something.
Its ok to change to DOT 5.1 or should i stay at DOT 3?

Thanks for help.

JACK RABBITz:
Silicone brake fluid is DOT 5.0. But Dot 5.1 is a conventional fluid with a higher boiling point than 3.0. I believe it's another poly-glycol Ether like the the DOT3.x types. It's been a source of confusion that the DOT used the 5.1 designation for a fluid that's not silicone. 5.1 does have the same problem with H2O absortion effect on boiling point that the other high weight ethers have.

Thank you for reply. But do you mean i can use that stuff without to crack my seals?

^ yes, it should be called DOT 3.1 instead.

JACK RABBITz:
If you actually are interested in Silicone fluids I have used DOT 5.0 in motorcycle brake and hydraulic clutch systems for more than 20 years with no problems at all. I've never used the 5.1 fluids but I believe others on this forum have with no bad effects. I wouldn't expect 5.1 to be damaging since it's of the same basic chemical content as the older style. You might check with GM or their website to see what they have to say about substituting 5.1 for 3.0.

hey01:
You're right, the naming conventions for brake fluids are not so logical. I think there already was a DOT 3.1 though. There is a DOT 4.0 ... I don't know if there is a DOT 4.1, though the boiling point of 5.1 is about another 70°F higher than 4.0 (which is about 45°F higher than 3.0) so I think it needed it's own number but 5.1 certainly doesn't seem right. (I wonder if it was a temporary summer intern employee or a typing error that led to this!)

Aha. The Problem is, on the DOT 5.1 is written "Silicon based fully synthetic brake fluid".

Hm, today one shop can order DOT 3, so the problem is at the moment outdated but for the future ill write to GM whats happend in Camaro 99 Z28 with brake fluids.

JACK RABBITz:
That's not right ... I wonder if the manufacturer meant to say "5.1 not compatible with silicon fluids" or the container label maker mangled the message?

This thread might answer some of your questions...:)

http://www.camaroz28.com/forums/showthread.php?t=522323&highlight=fluid

Oh, thanks for that link :)

@NJ-LE:

In the Camaro-Datasheets "BRAKE SYSTEM" is written, that the owner need to use DOT 3 and NOT DOT 5 silicon based synthetic fluid. Thats exactly written. Thats the reason for my question.

Here, i attach the picture:

http://people.freenet.de/jackrabbitz/Camaro/Brakefluid.jpg

I have DOT 5.1.
5.0 Silicion base for bikes it will eat sealing and other orings. Work Greak for Bike but not for our cars.
5.1 Works fine it will not Damage sleant or rubber o rings and washer.
However 5.1 does needs to be change every 3 years or so. It does attrack lot of mositure.
There is not point for this upgrade I did it because I had wild hair up in my arse:o

And did you not change anything on your car? You replace only with 5.1 and thats it?

And did you not change anything on your car? You replace only with 5.1 and thats it?

Well I was adding Front brake Lock (Allow you lock the front brake and rear wheels to be free) for my burn out for drag racing,
So beside that I didn't change any thing.
In all honesty I did not feel or think I gained a single dime out of it.
Matter of fact I am undoing the MOD (Removing Front Wheel Lock) I am going back to DOT3~
I have 96 MN6 TA

Silicone based brake fluids are not recommended because they tend to foam when passing through small passages, which means that ABS systems won't work properly. Also, silicone based fluids tend to be more compressible than glycol based, so it will feel a little spongy. Silicone fluids will not eat rubber parts but isn't compatible w/ regular fluids so it's either one or the other, they're not meant to be mixed. To be honest I don't see the need to change to that typed of fluid anyway, a good DOT 4 should work fine (3 & 4 are virtually the same as far as compatibility goes). Most braking problems I've seen are from brake fade and overheating pads/rotors, not from fluid boiling. A lot of higher end vehicles use ducting to keep airflow across the brakes so no special fluid is required that would inhibit ABS operation.

Silicone fluid use not as much for the high boiling point (never hurts though) but to avoid the sort of corrosion on the internal steel surfaces of the brake system that often occurs with poly-glycol ether brake fluids as vehicles age. Yes, I know manufacturers recommend complete brake system flushing of conventional fluids every few years to avoid this problem but few people do this (it's a pain).

Oh, good to know that. Next year ill try DOT 5.1.
If its the truth, that silicone is not eating rubber, then all is fine. If i have problems with ABS or something, then ill change the Fluid back to DOT 3.

JACK RABBITz:
Just be careful to minimize air bubbles in the fluid as you pour into the master cylinder. If you have any bubbles put the cover back on and give them time to rise to the surface to disappear. When bleeding don't let the master go dry and don't pump the brake pedal vigorously. Be slow and moderately firm with the pedal (slow on the release too) and ease the bleeders open and make sure your assistant doesn't cause any "suck back" by releasing the brake pedal before you close the bleeder. If you're using a hand vacuum pump to bleed with then use the least vacuum possible. Again this is to try to minimize the possibility of bubbles in the system. Of course, follow the usual precautions of 1) don't turn on the ignition (which will cycle the ABS unit) until you are compltely done. 2) bleed at the ABS block first then the usual sequence at the calipers. Good Luck

Thanks for help.

At my first changing 2 weeks ago, i let go the master go dry :(

After that realy big mistake ive pumped 4 Liters of DOT 3 to get a result nearly without bubbles.

1 week ago i bleed again 1 Liter and get only a few bubbles and after that only verry verry small ones. I dont know what i must do. I think one of the next weeks i will pump 1 Liter again to make sure, that ire bubblefree.

JACK RABBITz:
If the car is driveable and if you're using DOT3.0 you might want to call a few quality brake shops and inquire if they have the tools to cycle and home your Camaro's ABS block and what they would charge to pressure flush and bleed your brake system. It might be worth it to avoid more stomach churning aggravation! If you try that route please give us a post on the cost. (I have no idea what the cost would be.)