Brake fluid in Reservoir & above the seal - anyone else seen this?

[RealWing]

Doing a 2-year brake fluid flush and when I took the cover off, there was some fluid above the seal. I didn't expect to find fluid here, which seems to indicate the reservoir was not sealed tight. The fluid in the reservoir was quite dark, which indicates it was exposed to the air. I used a light and I can't see any holes in the seal. Anyone seen this??
Thx
Jim

Ps: I asked the lead tech at my dealer about a brake fluid flush at 2 years as per the manual and he said: "Literally never unless there is some other reason to take the system apart. As you likely know, you really don't use the brakes much, so that fluid doesn't really go bad."
Yeah right!!

 

[BajaRon]

Brake fluid goes bad in every vehicle, even if you don't use your brakes at all. That is a very odd statement from your dealer.

We've had customers come in with brake fluid filled to the top of the expandable seal. They just added fluid without taking the seal out first. Not saying that's your issue. But if your dealer is making statements like that. Who knows what else they might think is OK.

Your fluid definitely needs flushing! That looks like sewer water!

 

[RealWing]

Thanks Ron
That was the first flush after purchase in 2022. The cap had never been removed from when it was installed at the factory, unless the dealer opened it for a pre-delivery inspection.
Speed bleeders installed and all circuits flushed clear.
Jim

 

[BertRemington]

Concur with Ron. That is badly contaminated fluid in the reservoir.

WRT fluid above the separator seal, that could be water (via the cap) or brake fluid (via the edge). Neither is of much concern.

This is going to be a multi-stage process.

1) Start with at least 16oz of DOT 4 fluid (I use ATE 200). Remove most of the fluid from the reservoirs (always leave some fluid in the reservoir -- if you introduce any air life will get much harder), replace with new fluid and replace the caps with seal. Pump your brakes to make sure there are no leaks and you have pressure. Drive about 50 miles in local traffic, preferably rush hour, so you use your brakes often. If you're bored at a traffic lights, pump your brakes. Not hard, you're just trying to move fluid around. For the most part there won't be much new-old mixing, there will be some, but my major goal is trying to absorb water from the old fluid into the new.

2) You will need a friend to help. You will be removing all three wheels (one at a time would be best) and accessing the fluid bleed port on the brake caliper. Do not use open-end or 12-point tools on the bleed screw -- you will round the corners! I recommend replacing the Brembos bleed screws with Speed Bleeders. Replace most of the fluid in the reservoirs with new. With the help of your friend bleed each wheel until the fluid coming out is close to that in the reservoir. Check the reservoir level every 10 pumps of the brake pedal. Do each wheel in order (preferably LF -- RF -- R) twice. Put the caps with seals back on, verify brake firmness and do the 50 mile thing again.

3) Basically repeat Stage 2 with the goal of fluid color match between reservoir and caliper but without the 50 mile thing because your brake system is clean. Your second picture was taken with a White reservoir which means color balance was pretty good which means your fluid was at risk of damaging your brake system with corrosion. 160z of brake fluid probably won't be enough -- buy two.

Some members will correctly point out this doesn't flush the VCM. The VCM isn't that hard to access and I recommend you flush it too if you think you can. It's a bit more complicated than a caliper though so if you can't you still have reached the "Better than most folks" point. And apparently better than your dealer's.

Bleeding the brakes is simple but not easy and it's messy. Expect to spend several hours for each stage. Have plenty of cloth work towels (paper towels, unless they are the blue ones, really don't provide the needed absorbancy). You may be tempted to use brake cleaner spray. If so, sparingly as it's really unfriendly to many things especially wiring.

Best wishes.

 

[Flier Tuck]

From my basics knowledge of hydraulics and vehicle brake systems, brake fluid does not move around the system. It is simply a medium for transferring pressure from the master cylinder to the wheel cylinders. The fluid does travel in the pipes very slightly to move the pistons in the brakes but then returns when the brake is released; but it definitely does not move around the system.

 

[RealWing]

Photos of the fluid from the reservoir and wheel circuits. Definitely will have to check the reservoir fluid for contamination a lot more often!!

Speed Bleeders worked great.

Photo order is Reservoir, LF, Rear, and RF.

 

[BajaRon]

From my basics knowledge of hydraulics and vehicle brake systems, brake fluid does not move around the system. It is simply a medium for transferring pressure from the master cylinder to the wheel cylinders. The fluid does travel in the pipes very slightly to move the pistons in the brakes but then returns when the brake is released; but it definitely does not move around the system.

You are correct. There is a slight amount of exchange between the reservoir and the lines connected. But the fluid is nothing more than an energy transfer mechanism. The VSS module holds a small amount of fluid and it will exchange somewhat over time due to how it functions.

Photos of the fluid from the reservoir and wheel circuits. Definitely will have to check the reservoir fluid for contamination a lot more often!!

Speed Bleeders worked great.

The caliper fluids look much better than I would have expected having seen the reservoir contents. Something must have allowed a great deal of moisture into the reservoir. It should not have looked that bad after only 2 years. Are the 2st to pics fronts and the 3rd pic the rear?

 

[BertRemington]

From a pure hydraulic perspective (ie medium is inelastic) there is no old-new fluid mixing. From mechanical and chemical perspectives, there is old-new fluid mixing. Granted it's small but in my experience it's beneficial.

 

[RealWing]

Photo order is reservoir, LF, Rear and Rf

 

[BertRemington]

Yes you did an excellent job with file names. Racking my brains for why the color differences between calipers. I think it's related to different circuits for the fail-safe brake connectivity. But there are other possibilities... I really appreciate the detailed information you provided -- with photos!

 

[RealWing]

Yes you did an excellent job with file names. Racking my brains for why the color differences between calipers. I think it's related to different circuits for the fail-safe brake connectivity. But there are other possibilities... I really appreciate the detailed information you provided -- with photos!

The RF was done last and looked the best. so I suspect all the old fluid was mostly purged out of the lines?

 

[BertRemington]

Thanks. Cooling off my brains now. Will return to normal during beer cat time this evening.

 

[BajaRon]

The RF was done last and looked the best. so I suspect all the old fluid was mostly purged out of the lines?

OK, that makes sense as well.