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Old 12-10-2018, 09:56 AM   #1
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Brake fluid, time for a flush, what should I use

I had an oops last week, I was flushing the clutch and sucked in a big air bubble and it took all my on hand brake fluid to get it out:
  • .5 liter of Castrol SRF (recently opened, my current brake fluid)
  • 1 Liter of ATE Type 200 "Super gold" (new unopened container)
  • .5 liter of Motul 600 (new unopened container)

So now I have this combo of fluids in there, it did great at Sebring this weekend, but now I want to flush it all out and have a single fluid in there. Also 2-3 people at Sebring told me that Castrol SRF doesn't play well with other fluids.

The fluids I have used in the past are those same 3:
  • ATE Type 200 "Super Gold" - really liked it and ran with this for several years
  • Motul 600 - ran for maybe 18 months. Still getting soft pedal at the end of a 30 minute session at places like Sebring
  • Castrol SRF - heard this was the be all end all, not have to bleed after every track day, etc.. etc... It still got soft at the end of a long session at Sebring and still had to bleed every time

Since I am going with a clean flush, I thought this might be a chance to see what all is out there, what people are using and how they like it.

Tires are either Hankook R-S4 or a 100 TW r-comp like the Maxxis RC-1 and brakes are GLOC R-10 front R-8 back.

TBH I am thinking of going back to the ATE Type 200 "Super gold", the only thing is I don't have any and shipping is too much, and the Amazon Prime price is too high... Usually I buy it at the track from Linda at Apex...

The SRF didn't seem to be any better than the Motul 600, I talked with a husband/wife team at Sebring that track a modified 997 and a 987.1 Cayman, they run a shop somewhere and the Motul 600 is what they run.

Thoughts? What are you running and how do you like it?
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Old 12-10-2018, 11:29 AM   #2
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Correct, Castrol or for that matter any synthetic, will not play well w/ Dot 4 (or lower of course). Thus a complete flush and refill including clutch, is required when changing to synthetics (if system can handle synthetics). And yes, smart choice having ONLY ONE fluid in system at a time... unless emergency at which point a mix would be better than not enough

Personally, I run Castrol SRF and, knock wood, have had zero issues of breakdown during long sessions or a season. Never any issues previously either w/ ATE. In a season with ~ 4-5 bleed/flushes, ATE will be about break even cost-wise w/ Castrol SRF.

Seems you prefer ATE and had no issues so I'd stick with as it's a fine choice. Just order bulk a season or half season's worth from Linda (w/ some other stuff) and I'm sure she'll cut you a break on price & freight - she usually does. ATE has good shelf life (years) un-opened so you are fine w/ regards to storage.

Pick your favorite now and do a full flush (not just bleed) on all four corners plus clutch. Drive for a week or so and then do another complete 4 corner plus clutch flush. This should expel most mis-match remnants and you'll be good to go.

If you still have issues there's something else cooking and I'd start w/ brake booster or master cylinder...

Good luck
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Old 12-10-2018, 11:42 AM   #3
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Motul 600 is what I use and lot of my fellow track rats as well
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Old 12-10-2018, 11:44 AM   #4
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look at boiling points -

ATE is ... 500
Castrol SRF is ... 590
Motul 600 is ... 594
Motul 660 is ... 622

soft pedal is supposed to be from brake fluid near the caliper getting boiled by the high temp of the rotor. boiling makes little air bubbles. air is compressible. are you getting little bubbles at the caliper when you bleed? further, the brake fluids with high boiling points tend to be hydroscopic - they attract water. water lowers boiling point and makes fluid more susceptible to getting boiled. hence the need to bleed the high-end fluids more frequently. and if even the best fluid continues to boil, then perhaps you need better airflow, or new rotors (less rotor material means less heat mgmt ability). ditto pads. is it the front or back that is starting to cook-off - bet you've got no cooling on the back ... i've heard of 987's needing rear cooling because the pasm works the rears more than in a standard system.

if no little bubbles then the soft pedal is from something else. cheap pads off gassing? had that happen once. once. change in performance of abs as tires heat up? i've often thought that the chinzy way the car makes vacuum for the brake booster has something to do with it, and as the engine works harder, vacuum and boost increase? there's a reason porsche went to the tandem pump in the 9x7.
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Old 12-10-2018, 12:41 PM   #5
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Quote:
Originally Posted by The Radium King View Post
look at boiling points -

ATE is ... 500
Castrol SRF is ... 590
Motul 600 is ... 594
Motul 660 is ... 622

soft pedal is supposed to be from brake fluid near the caliper getting boiled by the high temp of the rotor. boiling makes little air bubbles. air is compressible. are you getting little bubbles at the caliper when you bleed? further, the brake fluids with high boiling points tend to be hydroscopic - they attract water. water lowers boiling point and makes fluid more susceptible to getting boiled. hence the need to bleed the high-end fluids more frequently. and if even the best fluid continues to boil, then perhaps you need better airflow, or new rotors (less rotor material means less heat mgmt ability). ditto pads. is it the front or back that is starting to cook-off - bet you've got no cooling on the back ... i've heard of 987's needing rear cooling because the pasm works the rears more than in a standard system.

if no little bubbles then the soft pedal is from something else. cheap pads off gassing? had that happen once. once. change in performance of abs as tires heat up? i've often thought that the chinzy way the car makes vacuum for the brake booster has something to do with it, and as the engine works harder, vacuum and boost increase? there's a reason porsche went to the tandem pump in the 9x7.
I get bubbles every time I bleed in front, so I guess I am working them pretty good... Backs are fine. I have GT3 brake ducts, maybe I might try the pelican mod to vent the fender liners and see if I can get some more air going through there.

This past weekend I had just put on new front pads, and they were really thick (like new pads are ) and it was a lot better. So I think I am just heating things up there. Sebring has a lot of high speed braking zones

T1 - soft brake
T3 - threshold brake 100+ down to about 60
T5 - medium
T7 - threshold braking from 110-115 down to around 40
T10 - threshold 110'ish down to about 60
T13 - soft brake
T15 - 105+ down to about 65
T16 soft brake
T17 long brake zone, 120 down to about 70

The SRF has a higher wet boiling point so my thoughts were I could bleed less and leave it in there longer, but found I was bleeding just as much after I got it.

And if I am bleeding that much, then my brake fluid is pretty fresh and not having time to absorb much water, so the higher dry boiling point of the Motul 600 would be fine, at slightly less than half the price of the Castrol SRF...

So I am leaning back to the Motul 600, and oddly the Amazon Prime price of that is about the same as I could get if I were to buy it in person from somewhere...
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Old 12-10-2018, 12:42 PM   #6
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rbf600, never any issue with PFC pads and gt3 ducts
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Old 12-10-2018, 05:01 PM   #7
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I used to go with ATE and never had any problems, but after looking at how baked the worn pads are, I decided to go with Motul 600. I flush and bleed every 6 months. Seems to work fine - no complaints and the brake pedal is always nice and stiff.
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Old 12-11-2018, 05:07 AM   #8
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Most top end brake fluids are fine - and it can be debated forever just like motor oils. I run Motul 660 as that is what the previous owner ran and it's fine. I ran Amsoil in my S4 because I bled it much more often and it was pretty inexpensive.
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Old 12-12-2018, 04:34 AM   #9
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Quote:
Originally Posted by thstone View Post
I used to go with ATE and never had any problems, but after looking at how baked the worn pads are, I decided to go with Motul 600. I flush and bleed every 6 months. Seems to work fine - no complaints and the brake pedal is always nice and stiff.
+1 I did the exact same thing. Now using the Motul 600. Flushing the same schedule. I do bleed before the track each time.
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Old 12-12-2018, 09:35 AM   #10
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Motul 600 has been flawless in my cars for 10 years. Not cheap but good.
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