Wilwood black brake fluid

[Siestarider]

Last fall I mounted a slightly used Wilwood BBK with all new Motul 600 fluid. Ran one track day on XP -10 pads and was not impressed. Bled brakes and found fronts produced nearly black fluid. Never seen that before, assumed maybe prior owner used something not very compatible with Motul, so ran all calipers to clean fluid.

Ran another track day and brakes were fine, just as good as stock. Ran last week and fronts felt a little mushy and pedal got longer as day went. Pulled the pads today, XP-10's worn out (I did not know Carbotech riveted pads, look thin but ok at caliper ports, beware) . Bled the front right and got the same black fluid.

In my experience Motul RBF 600 turns darker gold with age, not black. But I only have cast iron caliper experience with it.

No fluid leaks. No known possible source of contamination.

Is it some kind of chemical reaction with the aluminum calipers? Thanks for help.

 

[M-Sport fan]

Do those Wilwoods have dust boots?

I know that some do (the ones marketed more for street use) and some do not (the ones sold exclusively for road course use).

Maybe the RBF 600 is reacting with, and partially dissolving those boots (IF you have them), or they could even be coming apart on their own due to heat/age/oxidation, and coloring the fluid?

 

[jeffreylyon]

Is it some kind of chemical reaction with the aluminum calipers? Thanks for help.

I run RBF 600 on my race car with steel calipers in the front and Wilwood aluminum calipers in the back with no color changes (4 pedal-push bleed on each caliper after each weekend).

 

[Siestarider]

The Wilwood 6 piston caliper O rings are only component not either aluminum or stainless steel. But no fluid leaks, so presumably O-rings are working fine.

Since Jeffreylon has no visible effects with same fluid, must not be chemistry.

Did drivers side today, same nasty black fluid from caliper. Rather than speculate further I will contact mfr and see what they say, report back.

 

[Siestarider]

Wilwood tech says if my o-rings are good, then its more likely excessive heat in calipers turning fluid black. My rotors are cooled, but the CMB ducts cool rotors, not calipers. Makes sense that WW aluminum calipers do not have the heat capacity of stock cast iron. I admit I use them hard.

His recommendation is to use a less aggressive pad (he recommended their H series) and maybe different fluid too. So we have a clue.

 

[M-Sport fan]

Wilwood tech says if my o-rings are good, then its more likely excessive heat in calipers turning fluid black. My rotors are cooled, but the CMB ducts cool rotors, not calipers. Makes sense that WW aluminum calipers do not have the heat capacity of stock cast iron. I admit I use them hard.

His recommendation is to use a less aggressive pad (he recommended their H series) and maybe different fluid too. So we have a clue.

Time to try the Torque RT700, I guess.

No wonder some of the prototype (and even some GT class) cars have water cooled calipers!

The iron calipers should pull the heat out of the fluid quicker than alloy, but the aluminum ones should dissipate/transfer that heat to the atmosphere better and quicker than the iron does, and NOT 'hold onto' it as long.

 

[Siestarider]

Wilwood sells a high temp brake fluid EXP 600, I will probably try that next.

The problem apparently is too much heat transfer from pads to calipers. I can see how a different pad compound might be more insulating than the XP-10's, just have to try some and see what happens. Obviously have to transfer more heat to rotors rather than through pads to calipers.

Since i had none of these problems with stock setup, just another example of subtleties in "performance" mods being more problematic than stock. Bout all I can say is WW are lighter, and will probably work just as well as stock once I get a fluid/pad combo that withstands the abuse.

 

[Flagstang]

Get the wildwood 600 fluid and a set of the titanium heat shields

 

[Flagstang]

http://www.tceperformanceproducts.com/images/P1010065.JPG

http://www.tceperformanceproducts.com/service-parts/

 

[jeffreylyon]

Wilwood sells a high temp brake fluid EXP 600, I will probably try that next.

The problem apparently is too much heat transfer from pads to calipers. I can see how a different pad compound might be more insulating than the XP-10's, just have to try some and see what happens. Obviously have to transfer more heat to rotors rather than through pads to calipers.

Since i had none of these problems with stock setup, just another example of subtleties in "performance" mods being more problematic than stock. Bout all I can say is WW are lighter, and will probably work just as well as stock once I get a fluid/pad combo that withstands the abuse.

Maybe try the slotted higher spec'ed WW rotors? You're cooling the rotors from the inside, the slots throw off a little heat from the surface of the rotor where all the magic is happening. I race in a class where we have to use stock calipers and the best way I've found to keep from cooking them off is to keep the heat out of the caliper to begin with; all the ducted air in the world does squat when blowing on a rectangular hunk of steel.

If you want to experiment you could cut a copper shim that is the same size as the pressure side of the pad but extends beyond the outside of the caliper and mount a heat sink on extruding part of the shim. I've seen that put an end to over heating brakes on some heavy street stock oval racers.

 

[Siestarider]

Maybe try the slotted higher spec'ed WW rotors? You're cooling the rotors from the inside, the slots throw off a little heat from the surface of the rotor where all the magic is happening. I race in a class where we have to use stock calipers and the best way I've found to keep from cooking them off is to keep the heat out of the caliper to begin with; all the ducted air in the world does squat when blowing on a rectangular hunk of steel.

If you want to experiment you could cut a copper shim that is the same size as the pressure side of the pad but extends beyond the outside of the caliper and mount a heat sink on extruding part of the shim. I've seen that put an end to over heating brakes on some heavy street stock oval racers.

I may try the slotted rotors when these are worn out.

Copper heat sinks sound an outstanding idea. Except my 16" track wheels barely clear calipers, cannot even run normal inside balance weights within their swept radius. But if the idea were implemented via an insulator rather than a conductor pad, it could fit within caliper if both thin and stiff.

Wonder if a thin carbon fiber shim stuck to the back of each pad would help.

WW also sent me an email (I did both phone and email questions), reminded me its time to get out the temp paint and indicator strips and see what is going on in more detail.

Tracking with the intention of setting new PB's is endlessly entertaining.

 

[jeffreylyon]

Copper heat sinks sound an outstanding idea. Except my 16" track wheels barely clear calipers, cannot even run normal inside balance weights within their swept radius.

You could try a heat sink with two 90º bends to make a U shape with 1 leg of the U between the pistons and the back of the pad and 1 leg running parallel to the front/rear of the caliper. That would add a ton of surface area to cool the piston/pad interface and should stay out of the way of the inside rim of your wheels. I run 6UL's and have a ton of room between the front of the caliper and the back of the wheel spokes - not sure about the OZs. You could get artistic with the portion of the sink that is outside of the caliper to minimize how much it covers the caliper.

But if the idea were implemented via an insulator rather than a conductor pad, it could fit within caliper if both thin and stiff.

Wonder if a thin carbon fiber shim stuck to the back of each pad would help.

I think that you'd crush the CF shim at the first corner and light the resin on fire by the third. Titanium is the way to go (http://www.tceperformanceproducts.com/brake-pads/ - all the way at the bottom on the right), but it's just going to slow the inevitable - a 20 minute HPDE session will completely soak the insulator as there's nowhere else for the heat to go. Of course, the same could be said for the heavier OEM brakes. Heat is heat and, unless you take it away, it'll eventually cook off the fluid.

WW also sent me an email (I did both phone and email questions), reminded me its time to get out the temp paint and indicator strips and see what is going on in more detail.

I like the crayons better but I think that there's more granularity in the paint. I've never used the sticker but they look neat, if pricey.

Tracking with the intention of setting new PB's is endlessly entertaining.

The good news is that, evidently, you know how to threshold brake!

 

[Siestarider]

You could try a heat sink with two 90º bends to make a U shape with 1 leg of the U between the pistons and the back of the pad and 1 leg running parallel to the front/rear of the caliper. That would add a ton of surface area to cool the piston/pad interface and should stay out of the way of the inside rim of your wheels. I run 6UL's and have a ton of room between the front of the caliper and the back of the wheel spokes - not sure about the OZs. You could get artistic with the portion of the sink that is outside of the caliper to minimize how much it covers the caliper.

The way this WW caliper is built, its outside is curved to fit inside of rim with outside port at the center of the crescent. Its still a great idea, but will take some careful templating to see if there is enough clearance to reach and hold a copper structure at each end of caliper. I am going to take a closer look at feasibility. Thanks

I think that you'd crush the CF shim at the first corner and light the resin on fire by the third. Titanium is the way to go (http://www.tceperformanceproducts.com/brake-pads/ - all the way at the bottom on the right), but it's just going to slow the inevitable - a 20 minute HPDE session will completely soak the insulator as there's nowhere else for the heat to go. Of course, the same could be said for the heavier OEM brakes. Heat is heat and, unless you take it away, it'll eventually cook off the fluid.

Have to disagree on this one. I measured front caliper temps as 275 F stock. WW's must be hitting closer to 450 F to turn fluid black but not boil. The insulation only has to reduce heat transfer from back of pad to caliper for at most 6 seconds at a time (pulled up a lap, 6.0 sec to decel 120mph-48mph). The rotor is right there to store and dissipate heat, and its better cooled,

I like the crayons better but I think that there's more granularity in the paint. I've never used the sticker but they look neat, if pricey.

Since I have the strips and the paint, sunk cost. Part of my CMB duct research expense. But crayons sound cool, might be easier than paint.

The good news is that, evidently, you know how to threshold brake!

I just cannot get myself to invoke ABS even though, in theory, it should be a little quicker. Eventually if that is the only thing left to try I will.

 

[jeffreylyon]

Have to disagree on this one. I measured front caliper temps as 275 F stock. WW's must be hitting closer to 450 F to turn fluid black but not boil. The insulation only has to reduce heat transfer from back of pad to caliper for at most 6 seconds at a time (pulled up a lap, 6.0 sec to decel 120mph-48mph). The rotor is right there to store and dissipate heat, and its better cooled,

Wow - that's a pretty substantial difference. I guess 11# of weight loss/corner has a down side. I'm still skeptical that the insulators will be effective for a whole session just because there's so much contact and so little insulating material but at $60 a full set they're certainly worth a try.

Also, if you're peaking at 450º and aren't noticing fade maybe you're not chasing a real problem?

 

[Siestarider]

Wow - that's a pretty substantial difference. I guess 11# of weight loss/corner has a down side. I'm still skeptical that the insulators will be effective for a whole session just because there's so much contact and so little insulating material but at $60 a full set they're certainly worth a try.

Also, if you're peaking at 450º and aren't noticing fade maybe you're not chasing a real problem?

Wilwood has a solution. http://www.wilwood.com/PDF/Flyers/fl77.pdf

Insulated pistons.

If you read the brochure, it intimates brake fluid can locally boil at backs of overheated stock pistons. This would explain the less than solid pedal at the end braking for long straights, its not bad, just not as good as it ought to feel. So it is a subtle form of fade I was not familiar with.

They also sell better o-rings for tracking, so guess I will be upgrading pistons, o-rings and pads since my stock o-rings are probably degraded by the heat.

I find it hard to believe that I am the only Fist driver with WW BBK who runs them hard on track. Think I will go to Sebring next week for SCCA track night, find out what current setup will do (Carbotech 1521 pads) if I baby them a little. Then rebuild with the good parts and compare. When its figured out I will post results in Tracking section, this is probably the wrong section now that the black fluid problem is understood.

 

[Pete]

Wilwood has a solution. http://www.wilwood.com/PDF/Flyers/fl77.pdf

Insulated pistons.

If you read the brochure, it intimates brake fluid can locally boil at backs of overheated stock pistons. This would explain the less than solid pedal at the end braking for long straights, its not bad, just not as good as it ought to feel. So it is a subtle form of fade I was not familiar with.

They also sell better o-rings for tracking, so guess I will be upgrading pistons, o-rings and pads since my stock o-rings are probably degraded by the heat.

I find it hard to believe that I am the only Fist driver with WW BBK who runs them hard on track. Think I will go to Sebring next week for SCCA track night, find out what current setup will do (Carbotech 1521 pads) if I baby them a little. Then rebuild with the good parts and compare. When its figured out I will post results in Tracking section, this is probably the wrong section now that the black fluid problem is understood.

I've only had the issue of the fluid going black after track days. I normally just bleed the fluid out and call it a day. For canyon/mountain fun and daily driving I haven't had issues with the fluid. I run wilwood BP-40 on track and BP-20 for everyday use.

 

[Siestarider]

I've only had the issue of the fluid going black after track days. I normally just bleed the fluid out and call it a day. For canyon/mountain fun and daily driving I haven't had issues with the fluid. I run wilwood BP-40 on track and BP-20 for everyday use.

Yeah, I only had it with tracking too. But if you have experienced it with BP-40 pads, everything I have learned so far makes me believe you are also experiencing piston "hot spots" that boil the fluid enough to discolor it. I was hoping it was my pads, Carbotech xp-10's. But if you have seen it on BP-40 pads, it must be a heat transfer problem regardless of pad maker.

I just sent WW tech an email asking for thermblock pistons, o-rings, H and BP-20 pads, and a few other things. I hope to get over to Sebring next Wed, if I do I will try temp paint and strip indicators on calipers to see how much heat and where. Then put in the upgrades and measure again next track day.

At a track like Sebring, I do not believe braking is as important to lap times as getting turns 1 and 17 right. Still working on that.

However, braking for hairpin is strenuous, at least -70 mph. Then turn 10, probable -60 mph.

 

[Siestarider]

Update: WW priced the thermlock pistons for me, $537. Invoice looks like $47/each, no discount for buying 12.

Seems a little rich for 25% reduction in heat transfer from pads to caliper.

I am going to bail on Sebring tomorrow, its been raining like Monsoon here, Sebring is not well drained and Rival S not that good in rain. .

 

[jnathan68]

Saw your post in the who tracks their FiST thread and then went looking for this thread. Have the WW 12.19" kit with the 6 piston calipers and ran my first event about a month ago. Using ATE Blue and the Wilwood matrix B pads, I felt a lot of mushiness in the pedal and overheated the fluid (blue fluid came out black). Have used the ATE fluid in multiple other track cars in the past and never had an issue so thought maybe I had some pad rub leading up to the event combined with maybe left some air in them after the install and thus causing my braking issues. Bled them at the track and they held up ok for the the rest of the day.

Did a quick bleed on them again yesterday in preparation for another track day on Sunday. Hate to read threads like this and think I may have put on the wrong brake setup.

 

[Siestarider]

Saw your post in the who tracks their FiST thread and then went looking for this thread. Have the WW 12.19" kit with the 6 piston calipers and ran my first event about a month ago. Using ATE Blue and the Wilwood matrix B pads, I felt a lot of mushiness in the pedal and overheated the fluid (blue fluid came out black). Have used the ATE fluid in multiple other track cars in the past and never had an issue so thought maybe I had some pad rub leading up to the event combined with maybe left some air in them after the install and thus causing my braking issues. Bled them at the track and they held up ok for the the rest of the day.

Did a quick bleed on them again yesterday in preparation for another track day on Sunday. Hate to read threads like this and think I may have put on the wrong brake setup.

I just ordered WW H pads and their high temp fluid. Next track day I will measure temps with that setup, report how brakes feel and what if any discoloration there is.

Forums like this enable critical experience/analysis sharing among folks using similar gear. I end up on other forums frequently when researching (rennsport forum says Porshe Cup cars run Endless RF650 fluid $40/pint). If the WW fluid boils, next experiment would be that fluid.

Still a lot less than thermolock pistons at $550 a set. I approached WW about a group buy, then retracted, I have to be sure there is no other way to handle the heat before going to that expense.