Jelly in brake fluid - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

smg1138 · 07-14-2016, 08:40 PM

While I was installing new brake pads the other day I noticed a jelly like substance in the brake fluid reservoir. Anybody know what this is about? I'm using Motul RBF600 right now, but had the stock fluid before. This Motul fluid is around 9 months old and has been used mostly for street and AutoX. I've never seen this before, so any feedback would be appreciated.

Ultramaroon · 07-14-2016, 09:08 PM

way overfilled. Don't know if that contributed.

smg1138 · 07-14-2016, 09:10 PM

Quote:

Originally Posted by Ultramaroon

way overfilled. Don't know if that contributed.

No, the photos were taken right after installing the new pads. That caused the fluid to overflow into the reservoir. It's back to normal level now.

Ultramaroon · 07-14-2016, 09:49 PM

Quote:

Originally Posted by smg1138

No, the photos were taken right after installing the new pads. That caused the fluid to overflow into the reservoir. It's back to normal level now.

The only time I've seen gelatinous accumulation was the result of leaving E85 sit in a fuel system not designed for it. Is it possible ethanol got in there somehow?

smg1138 · 07-14-2016, 10:03 PM

Quote:

Originally Posted by Ultramaroon

The only time I've seen gelatinous accumulation was the result of leaving E85 sit in a fuel system not designed for it. Is it possible ethanol got in there somehow?

Since the weather got warm I've been using E85 most of the time. But, how would that affect the brake fluid? Doesn't seem like it could be related.

Ultramaroon · 07-14-2016, 10:13 PM

Quote:

Originally Posted by smg1138

Since the weather got warm I've been using E85 most of the time. But, how would that affect the brake fluid? Doesn't seem like it could be related.

It won't be unless somehow your brake fluid was contaminated with it. Do you see any contamination down in your reservoir, or is it just in your fill strainer?

Swagopopotamus · 07-14-2016, 10:14 PM

I've seen something like this happen when someone mixed dot 5 which is silicone based and dot 5.1 or dot 4 which is glycol based.

Not sure what the car comes with, but if you added the wrong fluid be ready to flush the whole system.

Sent from my iPhone using Tapatalk

Ultramaroon · 07-14-2016, 10:19 PM

Quote:

Originally Posted by Swagopopotamus

I've seen something like this happen when someone mixed dot 5 which is silicone based and dot 5.1 or dot 4 which is glycol based.

Not sure what the car comes with, but if you added the wrong fluid be ready to flush the whole system.

Sent from my iPhone using Tapatalk

I just googled and came up with this exact explanation - mixing silicon-based with glycol-based formulas. Not saying that's it but...

smg1138 · 07-14-2016, 10:36 PM

I've never used DOT 5 brake fluid in this car. I believe the stock brake fluid is DOT 3 and the Motul fluid is DOT 4. To my knowlege, DOT 3, 4 and 5.1 are all compatible, correct?

CCJ · 07-15-2016, 01:27 AM

Quote:

Originally Posted by smg1138

I've never used DOT 5 brake fluid in this car. I believe the stock brake fluid is DOT 3 and the Motul fluid is DOT 4. To my knowlege, DOT 3, 4 and 5.1 are all compatible, correct?

http://www.stoptech.com/technical-su...rs/brake-fluid

Shankenstein · 07-15-2016, 10:51 AM

As CCJ's link states, DOT4 will more readily absorb water and other contaminants than DOT3 (which is probably what our cars came with). Also, it's worth noting that most tech sheets for brake fluids (like Valvoline, Castrol, ATE, Motul, etc) recommend that you are careful to avoid mixing different fluids. The chemical differences between DOT3, 4, and 5.1 won't make them immiscible, but if you are tracking the car... the weakest fluid will degrade first.

I wouldn't worry about it too much. Scoop the goo, pull the fluid from the reservoir using a turkey baster or similar syringe, then thoroughly flush the system. If you have access to a powerful vacuum bleeder, I'm guessing that it would help move any gelled fluid stuck in the system.

Racing brake fluid is only intended to be in the system for a year or two... so if you're an infrequent racer (like me), it's best to flush the system for the first big event of each season.

Also, if you're car is seeing cold weather (significantly below freezing), it can cause gelling. Usually the viscosity returns to normal, but some chemicals separate and misbehave at very low temperatures. My company uses plenty of epoxies and industrial coatings, and some have warnings "Throw away if it sees freezing temperatures." because of the separation issues cause permanent changes that lead to clogged dispense nozzles or inconsistent curing.

renfield90 · 07-15-2016, 01:43 PM

It's caught by your screen filter. It could just be dirt or something that's jelled up. If the fluid deeper inside is jelly-free I wouldn't worry.

Swagopopotamus · 07-15-2016, 04:21 PM

Quote:

Originally Posted by Norville Rogers

E85 in the hydraulic braking system? Good tip from someone who didn't know that replacing brake pads will cause the brake fluid to rise.

Maybe he added ethanol to increase the octane rating of his brake fluid.

smg1138 · 08-05-2016, 11:24 AM

Just wanted to post an update on this. I flushed the Motul RBF600 and replaced it with Castrol SRF. The jelly appears to have completely gone away now. Still have no idea what caused the Motul to do that.

07-14-2016, 08:40 PM	#1
smg1138 Senior Member Join Date: Jan 2014 Drives: 2013 Raven FR-S Location: Nashville Posts: 775 Thanks: 968 Thanked 213 Times in 136 Posts Mentioned: 3 Post(s) Tagged: 2 Thread(s)	Jelly in brake fluid While I was installing new brake pads the other day I noticed a jelly like substance in the brake fluid reservoir. Anybody know what this is about? I'm using Motul RBF600 right now, but had the stock fluid before. This Motul fluid is around 9 months old and has been used mostly for street and AutoX. I've never seen this before, so any feedback would be appreciated.

07-14-2016, 09:08 PM	#2
Ultramaroon not playing cards Join Date: Sep 2014 Drives: a 13 e8h frs Location: vantucky, wa Posts: 32,382 Thanks: 53,019 Thanked 37,199 Times in 19,297 Posts Mentioned: 1117 Post(s) Tagged: 9 Thread(s)	way overfilled. Don't know if that contributed. __________________ service manuals

07-15-2016, 10:51 AM	#11
Shankenstein Frosty Carrot Join Date: Jan 2013 Drives: The Atomic Carrot Location: Baltimore, MD Posts: 513 Thanks: 272 Thanked 430 Times in 199 Posts Mentioned: 19 Post(s) Tagged: 0 Thread(s)	As CCJ's link states, DOT4 will more readily absorb water and other contaminants than DOT3 (which is probably what our cars came with). Also, it's worth noting that most tech sheets for brake fluids (like Valvoline, Castrol, ATE, Motul, etc) recommend that you are careful to avoid mixing different fluids. The chemical differences between DOT3, 4, and 5.1 won't make them immiscible, but if you are tracking the car... the weakest fluid will degrade first. I wouldn't worry about it too much. Scoop the goo, pull the fluid from the reservoir using a turkey baster or similar syringe, then thoroughly flush the system. If you have access to a powerful vacuum bleeder, I'm guessing that it would help move any gelled fluid stuck in the system. Racing brake fluid is only intended to be in the system for a year or two... so if you're an infrequent racer (like me), it's best to flush the system for the first big event of each season. Also, if you're car is seeing cold weather (significantly below freezing), it can cause gelling. Usually the viscosity returns to normal, but some chemicals separate and misbehave at very low temperatures. My company uses plenty of epoxies and industrial coatings, and some have warnings "Throw away if it sees freezing temperatures." because of the separation issues cause permanent changes that lead to clogged dispense nozzles or inconsistent curing. __________________ If you think you're nerd enough, join in the discussions about Suspension and Aerodynamic modelling! Wall of Fame - JDL Auto Design, Raceseng, Vishnu Tuning, Penske Shocks, Nameless, Perrin, RaceComp Engineering, Essex/AP Racing, Verus, RacerX Wall of Shame - aFe Takeda, Wilwood, FA20Club

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07-14-2016, 10:14 PM	#7
Swagopopotamus Member Join Date: Jun 2016 Drives: Not an FRS, but same initials. Location: Sin City Posts: 72 Thanks: 31 Thanked 51 Times in 27 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	I've seen something like this happen when someone mixed dot 5 which is silicone based and dot 5.1 or dot 4 which is glycol based. Not sure what the car comes with, but if you added the wrong fluid be ready to flush the whole system. Sent from my iPhone using Tapatalk

07-14-2016, 10:36 PM	#9
smg1138 Senior Member Join Date: Jan 2014 Drives: 2013 Raven FR-S Location: Nashville Posts: 775 Thanks: 968 Thanked 213 Times in 136 Posts Mentioned: 3 Post(s) Tagged: 2 Thread(s)	I've never used DOT 5 brake fluid in this car. I believe the stock brake fluid is DOT 3 and the Motul fluid is DOT 4. To my knowlege, DOT 3, 4 and 5.1 are all compatible, correct?

07-15-2016, 01:43 PM	#12
renfield90 The Stig's German cousin Join Date: Mar 2013 Drives: 2013 FR-S Location: Tempe, AZ Posts: 1,071 Thanks: 140 Thanked 519 Times in 345 Posts Mentioned: 8 Post(s) Tagged: 2 Thread(s)	It's caught by your screen filter. It could just be dirt or something that's jelled up. If the fluid deeper inside is jelly-free I wouldn't worry.

08-05-2016, 11:24 AM	#14
smg1138 Senior Member Join Date: Jan 2014 Drives: 2013 Raven FR-S Location: Nashville Posts: 775 Thanks: 968 Thanked 213 Times in 136 Posts Mentioned: 3 Post(s) Tagged: 2 Thread(s)	Just wanted to post an update on this. I flushed the Motul RBF600 and replaced it with Castrol SRF. The jelly appears to have completely gone away now. Still have no idea what caused the Motul to do that.

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