Topic: Brake reservoir "racing" cap

[lil goat]

We know the brake fluid boils, you can see it overflow from boiling. This is not just on the Kappa, very common problem that's why Castrol can charge $80 for high temp brake fluid. How is it overflowing if it is not all hot? What Bob said makes sense, but somehow the stuff IS boiling over. Next time you come off the track open the cap and stick your finger in the fluid and report back how hot it is, or if you must use a thermometer. I am not much of a scientist/engineer don't car what causes the problem, more interested in how do we fix it.

Getting back to my boiling water analogy, it takes a lot more heat to boil 2 quarts of water than it does 1, that's why I bought a bigger reservoir.

[Critterman]

Simple solution for the over flow problem.  Brake fluid is in a restricted space as it gets hot at the calipers it (like all fluids) expands and needs more room, so either the lines swell or it pushes back throught the lines, valves, and everything else in it's way back to the resevoir (had to look ).   That is my best guess.

[kennysabarese]

if the brake fluid was actually boiling inside the reservoir at 400+ degrees, wouldn't it melt the plastic?

[snaponbob]

if the brake fluid was actually boiling inside the reservoir at 400+ degrees, wouldn't it melt the plastic?

As the clouds separate, the sky is visible !!!!!!!!!!!!!!!!!!!

[numbbers]

So, what is the consensus?  Opel resovoire, billet cap, or both?  I am about to install the Willwoods on the Mallett, and I don't want to go through the bleed process twice.  The racing fluid is too damn expensive to waste.

[kennysabarese]

are you actually racing?

[Uranium-238]

I know that with the stock fluid, the stuff suspected of boiling, water contamination was a VERY real possibility. When brake fluid won't strip paint you really have to wonder...

[kennysabarese]

The current argument is to determine if the fluid boils in the reservoir or not.

[Uranium-238]

I dunno the specs on the stock fluid, but I do know some DOT 3 fluid can boil at temps as low as 140* when it's really saturated with water. Even if the effects of heavy breaking only have a slight impact on the reservoir temps, it could be enough to push things over the edge.

[kennysabarese]

yes, but some still do not believe that it actually is boiling inside the reservoir. just in the caliper and lines.

others do. we just don't know.

[lil goat]

if the brake fluid was actually boiling inside the reservoir at 400+ degrees, wouldn't it melt the plastic?

I wonder the same thing, but it seems this is a common problem, lots to read about it on the interweb. From what I read it is the water in the fluid that boils creating steam, steam being a hot gas rises and needs to escape, it goes to the top and bubbles out, not sure the brake fluid is actually boiling per say but that is the term used to describe what is happening. I think with new Dot 4 fluid what you are seeing is expansion due to heat, causing overflow.

[snaponbob]

yes, but some still do not believe that it actually is boiling inside the reservoir. just in the caliper and lines.

others do. we just don't know.

There are physical changes and activities that are occurring in the calipers when "boiling" occurs. If there is moisture in the brake fluid and it "boils", when everything cools off, the brake fluid will absorb the moisture again. If there is enough expansion, then the fluid level will rise in the reservoir. Assuming NO spillage, the level will return once cooling takes place. If there are any high spots in the lines any air pockets will gather there. Race teams bleed brakes in the pits to expel any gas pockets from the calipers which leads one to believe that the gas pockets are not traveling very far. Over time, if pockets do develop in the caliper, when they heat up it develops pressure in the system that can actually cause brake drag in that circuit and a vicious cycle starts that can even lead to brake lock up. This was more of a problem in drum brakes as wheel cylinders can (and do) more easily pull air in past the seals than might happen in disk calipers.

Personal experience with air that did NOT move in a brake system. HOW this happened I do not know, but I know what it caused and what the fix was. Over time the rear brake circuit on my 97 Chevy Express van became weaker and weaker to point that they were nearly non-functional. Repeated attempts to bleed the brakes resulted in no improvement. Finally I got my hands on a Tech2 scan tool (the only way to activate the ABS pump on my system), and cycled the ABS system. I had suspected air in the system and it sure was there - TRAPPED down stream of the master cylinder IN the rear circuit of the ABS pump. Even with forcing ABS action on gravel roads the air stayed put. Once the pump was cycled, an incredible amount of air came out of the rear circuit. Why do I share this? The assumption that "air" is going to get from any caliper, through the ABS system, past the master cylinder and into reservoir may not be correct. IF there is moisture in the fluid, it was slow absorbed into the brake fluid a) when it was poured into the system (and even on a 100% humidity day there will not be THAT much absorbed to affect the system), or b) over time as the fluid is agitated in the reservoir and contacts ambient air that is constantly vented through the cap. All ABS systems are vented to allow the fluid "room" to move when/if the ABS pump is activated.

[lil goat]

I was looking at stuff for my sons GTO and stumbled on this on the Z06 website, I just found it interesting.

You can upgrade the OEM Master Cylinder a number of ways, but should be done only to improve performance if there IS a definite need or problem.

1. The easiest and cheapest is to replace the reservoir with a larger one. This will allow for more fluid to be retained in the system and presumably help keep the fluid at a lower temperature and add a small window of safety. This is done on some cars that see the track.

2. Upgrading to a larger Master Cylinder ergo with a larger bore and piston area. This may be done IF you have also increased the caliper piston area by adding bigger calipers with more caliper piston area; such as 6 piston calipers in the front and larger 4 pot rear calipers.

Be aware that Master Cylinder piston area needs to be specifically matched to Caliper piston area. The OEM MasterCylinder may have enough area to support the addition of some larger front calipers only. If you do not increase the Caliper piston area by adding "big brakes" and add a larger Master Cylinder with OEM Calipers you will degrade performance as the line pressures will decrease.

[snaponbob]

The master cylinder thing is a great idea. However, finding such an item for a Kappa may be a challenge. In speaking with Wilwood and a couple of their vendors, all say that the front calipers for the Kappas have nearly identical fluid volumes and they said the stock MC should be fine. Heck, everybody that has done calipers has said the same thing - "firmer pedal, and better response", so the need for a bigger M/C probably is not there.

So, is lil goat gonna become lil yellow jacket??????????

[Treeman]

So, is lil goat gonna become lil yellow jacket??????????

He does buzz a lot.....

[lil goat]

It says pretty clearly in what I posted we DON'T new a new master cylinder, that was my point. Not that we do, I am using the same master cylinder just a larger reservoir as it mentions. It is installed and I posted the pictures.

[snaponbob]

Understood. Was only addressing item two. Do you know how much larger the capacity is on the bigger reservoir?

[lil goat]

No body faint but I posted pictures, it held about half a liter when we filled it up. Not sure what the factory one holds, it's a lot bigger.

[kennysabarese]

I got the cap extender today. I'll try it out this weekend.

[kennysabarese]

Here are pics of the cap extender. not sure what the little disc is for.

[lil goat]

The little disk goes inside the master cylinder under the cap to help prevent overflow, that is some high tech science there. Could have just used a cork. It is pretty though. (there are pictures of it in place in the Solstice book)

[kennysabarese]

yeah i haven't looked at the directions in the book yet. gunna play with it saturday or sunday.

[kennysabarese]

I installed the cap today. It was simple. It's in the Solstice Performance Book, which has better photos. But I'll go through the process.

The issue is that the fluid spills over the edge like this and makes a mess on the wheel fender.

[attachment=1]

First, take off the cap, I used a paper towel and rubber band to keep snow from getting in there, then yank out the inside rubber part of the cap
[attachment=2]

[attachment=3]

[attachment=4]

Pop the inside into the bottom of the extender, I used a screwdriver to make sure it was in there solidly and flat.
[attachment=5]


pinch the inside and pop it out, then cut 3/16ths of it off. The extender part is done, you can pop the cap on now or do it later.
[attachment=6]

[attachment=7]

[attachment=8]

[kennysabarese]

You can then put the cap on or leave it to later, grab the disc, and head back to the car.

[attachment=1]

[attachment=2]

Back at the car, take the little disc, pop it in as you see here, you'll notice the grooves on the bottom of the disc correspond to the ridges in the reservoir opening. It takes some pressure, but it'll go in there.

[attachment=3]
[attachment=4]
[attachment=5]


And that's it!

[snaponbob]

It's a C&C'ed baffle !!!!!!!!!!!!!! Cool. Dude, you must have had severe cabin fever to do that today!!