Brake Bleeding Questions on S2

ChasR · Oct 27, 2009

I am about to change the brake fluid on my 944 S2 as a matter of course (I'll also be changing the front castor mount to 968 items, getting the car tracked and giving it a full service (oil, filters etc.). Of course it's a little different to a normal braking system in the sense that it has two nipples per caliper. In the past I have seen people only bleed off the brakes using one nipple out of the two on 4 pots but have always been a bit dubious about this myself.

Besides going from the furthest run (O/S Rear to N/S Rear to O/S Front then N/S Front) what sequence should I attack the nipples with? Should I do the furthest out nipple first or second, or repeat the bleeding process after I have done one set of nipples?

I know it sounds a little silly picking at details like this but I figure it's best to be safe rather than sorry.

Final question is does ATE Blue have any significant advantage over normal DOT 4?

Alexw · Oct 27, 2009

I did this not long ago, with ATE Racing Blue as it happens, I did the furthest one out first as that made the most sense to me. The best part of using the Blue is its easy to see when the new stuff is coming through! Many people have recommended it on this site in the past, mostly people who track theirs regularly.
I think I did one full circuit - all 8 nipples, then another to make sure. Then took it out for a test drive then brought it back and bled one last time. To be honest the last 2 did very very little, but better safe than sorry, and I still used less than a litre.

Hilux · Oct 27, 2009

Final question is does ATE Blue have any significant advantage over normal DOT 4?

Yes, a higher boiling point.

DOT 4 fluids are perfectly fine for road use (unless you drive it like you stole it in Milton Keynes)

sawood12 · Oct 27, 2009

It is like most things in life in that not all DOT 4 fluids are the same - there are those that are better than others e.g. ATE DOT 4 fluid is better than your plain vanilla Halfords stuff. Boiling point is not the only factor that differentiates the better fluids. Absorbsion of water is another factor in that a better fluid wont absorb moisture as readily as cheaper varieties. ATE is a very good fluid and is good for road and trackdays. My philosophy on things like this is don't scrimp and get the good stuff (not that ATE is particularly expensive).

Frenchy · Oct 27, 2009

I have a one man brake bleeder kit from Draper which has 2 pipes and 2 one way valves for calipers with douple nipples....super smashing lovely !

zcacogp · Oct 27, 2009

As has been said already. One-man bleeding kits are very useful (although I have a boring 'normal' one, not one such as Frenchy describes), and work your way 'round all the calipers in turn, doing both nipples for each caliper, giving the calipers a good thump as you do them to dislodge any air bubbles from the inside of them. Take car not to round any nipples off or snap them, and life will be good.

FWIW, I used some ATE fluid when I did it a couple of years ago, and some GM fluid when I did it a couple of months ago, The GM stuff seemed to be better, to my mind, than the ATE stuff. (When it was done with the ATE stuff it didn't strike me as being a massive improvement. Doing it 2 years later with GM stuff was revolutionary, although it is possible that I simply did a better job, leaving less air in it, or similar.) Perhaps the same maxim applies as does to oil; doing it regularly is more important than using the most expensive fluid you can get your hands on.

Oli.

ETA: Both ATE and GM stuff were DOT4, which is more than fine for a daily-driver machine such as mine.

plenty · Oct 28, 2009

The ATE Blue resists boiling hence is well suited for track use. Obviously this isn't much of a benefit for a road car, though ATE Blue is priced well enough to serve as a good general-purpose fluid.

If the brakes haven't been bled for a while there is a small possibility of seized nipples. A good brake spanner is a must and Plus Gas on standby isn't a bad idea. I've had good results with the Gunson Ezi-bleed one-man bleeder product.

Hilux · Oct 28, 2009

not all DOT 4 fluids are the same

They all have to meet a minimum standard - DOT 4.

Halfords will meet that standard, others 'may' be better but in in marginal or specific ways with regard to wet and dry boiling points and the price reflects this.

ATE certainly has a higher wet and dry boiling point but Halfords is fine for road use however (in theory) needs changing more frequently.