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Why did brake fluid turn black, scorched?

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Old 05-29-2004, 12:04 AM
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Car: 85 IROC
Engine: 355
Transmission: Tremec 5 speed
Why did brake fluid turn black, scorched?

I recently had my 85 IROC at a road race course and after 2 days on the track the brake fluid is black. Has anyone else had this happen? Any theories on why this happened?

Here are more details:
-The brake fluid (Ford high performance, 570 deg dry boiling point) had only been in the system for about 2 weeks before the track event so it was not black from age and moisture. In fact it looked fine when I went to the track.
-I recently upgraded the front brakes from the stock units to the LS1 setup with aluminum calipers. This track event was the first heavy braking track I drove at with the LS1s up front.
-The brake fluid never turned black like this with the stock front brakes.

Could the aluminum calipers be transferring more heat to the brake fluid than the stock iron calipers, such that the fluid scorched and turned black?
Old 05-29-2004, 01:20 AM
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My obvious answer- You severely overheated the system. How'd your wheel bearings fair? Bet they arn't pretty either- The will most llikey make noise once you drive it again if not already.
Old 05-29-2004, 10:07 AM
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the problem seems obvious the ford fluid does not like gm components


j/k

on a serious note i'd agree with above. the system has been overheated badly.
Old 05-30-2004, 01:31 AM
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Axle/Gears: 7.625", Eaton Posi, 3.73
The fluid has simply been over heated. The Ford fluid is OK...but it's certainly not great. Very common on Road Race cars to have to change the brake fluid after every weekend...sometimes after every race, especially if using a mineral fluid such as the Ford stuff.

You really should be using a full synthetic brake such as Motul RBF 600. Will withstand much, much higher temps than mineral brake fluid. Note...this is a Synthetic brake fluid...not a Silicone brake fluid. Never use Silicone fluid in a competition car.

Run synthetic axle bearing grease as well. Amsoil is excellant as is Mobile 1.

Run some air ducting to the brakes. It will help a lot.

I ran a J65 setup ( 10.5" fronts and 12" rears ) over a full race weekend a couple of years ago. Took a lot of work to make them live. Temps on front rotors approached 1000c ( glowing at high noon!! ) but Motul RBF 600 fluid never faded or boiled.

Edit: What type of pistons are in the LS1 calipers? They should be stainless steel. SS acts as a heat barrier. Some older Vette brakes have SS bores and Aluminium pistons. This is a HORRID combination for racing as the Aluminium pistons will conduct heat much more readily than SS pistons...directly to the brake fluid, those boiling it and turning it black.

Yes, aluminium calipers may conduct more heat to the fluid than a Cast Iron caliper. It will also dissipate it faster. Radiant heat from the rotor plays a surprisngly large part in this. That is why you see "Top of the Line" Aluminium with Stainless Steel heat blocker plates ling the inside of the caliper. This stops radiant haet from the rotor from being absorbed as quickly as and unprotceted caliper.

And of course...you may have just been using those new brakes just a weeeeeee...bit harder than before.

Add some air ducting and switch to a full synthetic fluid such as the Motul and your problems should be solved.

If not...talk to me about water sprayers

Last edited by Chickenman35; 05-30-2004 at 01:44 AM.
Old 05-30-2004, 10:09 PM
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Thanks for the opinions guys. This is what I thought as well, fluid was cooked.

What really suprised me was that this never happened before. I have been driving my car at race tracks during open track days/driver schools for over 10 years. Until this year, I was running the J65 setup (10.5" rotors/single piston iron calipers). So like you Chickenman35 I have had seriously high front brake temps. I have no reports of my rotors glowing cherry red though. I run two 3" brake ducts to each front rotor, keep fresh fluid in the system, and run Mobil 1 synthetic grease in the wheel bearings.

I have heard about water injection. Tell me more. I like to think I'm the king of "do it yourself" with inexpensive parts and materials adapted to work in ways never intended. My plan for water injection is to use the windshield washer tank/pump to spray water into the brake duct hoses.
Old 05-31-2004, 02:05 AM
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Car: 86\92 Mutant
Engine: 355CI 430HP
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Axle/Gears: 7.625", Eaton Posi, 3.73
Originally posted by z28cdoyle
Thanks for the opinions guys. This is what I thought as well, fluid was cooked.

What really suprised me was that this never happened before. I have been driving my car at race tracks during open track days/driver schools for over 10 years. Until this year, I was running the J65 setup (10.5" rotors/single piston iron calipers). So like you Chickenman35 I have had seriously high front brake temps. I have no reports of my rotors glowing cherry red though. I run two 3" brake ducts to each front rotor, keep fresh fluid in the system, and run Mobil 1 synthetic grease in the wheel bearings.

I have heard about water injection. Tell me more. I like to think I'm the king of "do it yourself" with inexpensive parts and materials adapted to work in ways never intended. My plan for water injection is to use the windshield washer tank/pump to spray water into the brake duct hoses.
Great minds think alike...That's exactly what I did. Used the W\Wash tank as a reservoir. Had to add an auxilary pump though, as the one in tank is " timed" and activates the wipers. Universal Trico pump worked slick. Used horn button to activate motor. Disconnected terminal from horn(s) and hooked up to Trico motor. Nice, easy to reach switch that I could now operate manually.

For the sprayers I went to the gardening dept of my local Home Depot. Look for the 1\4" plant irrigation fittings. All sorts of fine sprayers with adjustable fluid volume. Dirt cheap. I finally settled on some 360 degree misters. Suspended them in the end of the ducting with some stiff Piano wire. Worked fanatastic!!!

I could use the sprayers just before or after a hard braking zone to reduce the rotor temps as needed. Never had any fade, and pedal was rock hard throughout weekend. I was using the J65's on a track that is notoriously hard on brakes.

Hawk Blues up front and Bendix Titanium on rears. Bendix pads held up excellant and I tend to run a lot of rear bias. They are rated " FF" .

Brakes started to go away at the end of the weekend. No boiling of fluid and pedal stayed rock hrad...car just didn't seem to stop as well.

Inspection after the final race showed why. The front pads got so hot that the backing plates expanded and seized in the caliper frame. Then the temps got so high that the backing plates softened. The front pads were actually BENT...so that only about half of the pad was contacting the rotor. No wonder it didn't stop as well!!!

Even under these extreme conditions, the combination of the Motul RBF600 fluid, 3" air ducting and the water sprayers managed to keep things alive. Of course the front rotors were toast...but it wasn't until Sunday afternoon that they really started to wear badly. I figure that happened when the pads seized in the calipers and the temps went to the moon. Up until Saturday morning, rotor wear and condition was surprisingly good.

Ran three different races. Novice CW race ( to get my Licenses upgraded ), Senior CW and a Solo 1 session. Races were 1\2 hr and Solo1 sessions 15 minutes. Plus all of the parctice and qualifying. Pretty good for little ol' J65's Amazing what they can do LOL.
Old 05-31-2004, 05:55 PM
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That water sprayer is quite the idea. Is it not at all possible to warp the rotor in any way by doing this??? I guess because its just a mist and not a large amount or its not that cold or what?
Old 05-31-2004, 07:45 PM
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Axle/Gears: 7.625", Eaton Posi, 3.73
Originally posted by DoBeR
That water sprayer is quite the idea. Is it not at all possible to warp the rotor in any way by doing this??? I guess because its just a mist and not a large amount or its not that cold or what?
If you sprayed the rotors with a heavy stream then yes...you could crack the rotor. But being a mist there is little thermal shock. Most of the water instantly turns to steam upon contact with the rotor. At very high rotor temps it is unlikely that the water even contacts the rotor. Gets vaporised before contact. This does reduce a lot of latent heat in the air stream though and is very effective in cooling the rotor.

Water spraying is nothing new. Has been in use for decades. Modern day Trans-Am cars use it....as do Logging trucks.

BTW...rotor warping is a myth. Rotors do not warp unless you do something stoopid like keep the brakes pressed on while in the pits. A good crew chief should box your ears for that, LOL

For the real answer to " Warped Rotors" check this out:

http://stoptech.com/whitepapers/warped_rotors_myth.htm
Old 05-31-2004, 09:10 PM
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Do you have any pictures of your fancy cooling system??
Old 06-01-2004, 03:01 AM
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Originally posted by DoBeR
Do you have any pictures of your fancy cooling system??
No sorry...
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