Stryder-Ryder

Something weird is happening. I had topped off the brake fluid reserviors (both front and rear) a week or more ago. Today I gave the Jeep a bath and had ran some Sea Foam through the manifold the clean things up. I glanced at my brake fuild reservior and the front is filled to overflowing to the point of weeping out the top and the back one is quite low.

I have no spotting that I can find from leaky lines that I can find. There was a bit coming straight down from the weeping top of the front reservoir but no where else.

Why would my front reservior fill to overflowing and the rear get so much lower?

seed

at the risk of sounding like a complete retard.......theres a rear brake fluid reservior?

BlueXJ

Master cylinder is divided inside into two chambers one of which feeds the rear brakes, while the other feeds the fronts.

jamaicanmecrazy

Slightly hung caliper or wheel cylendar causing your fluid to boil.
If you have large tires then drain the system and use silicone brake fluid as it doesn't boil off.

seed

but can't you just use the one outside the master cylinder?

Stryder-Ryder

I have not heard the great things about Silicone brake fluid... problems with moisture and sealing.

I have 31" BFG ATs for a nice comfy fit without cutting.

I was wondering if people had experienced an issue like this? It is possible that I was being an ID 10 T and overfilled the front and underfilled the rear; but... I don't think that happened. Not seening any leaks. I don't think fluid should be able to travel between reserviors unless something is broken.

Your thoughts...

BlueXJ

What one outside the master cylinder? You lost me seed.

jamaicanmecrazy

Think; it didn't leak out and was level in both resivoirs.
Must be boil over or the proportion valve is sticking.

Understanding Brake Fluid
Automotive brake fluid has many responsibilities. Corrosion protection and lubrication of brake system components are only a portion of the role brake fluid must play. All automobiles that have a hydraulic braking system must use brake fluid in order for the brake system to operate. The type of fluid used can depend on the type of vehicle and the demands of the vehicles brake system.
The two most common brake fluids used in the automotive industry are fluids that contain Polyalkylene Glycol Ether and fluid that contains Silicone or Silicium-based Polymer. Both Fluids are common but very different in regards to the manner in which they perform. Fluids containing Polyalklene Glycol Ether are more widely used and are the only fluids that should be used in racing brake systems.
Because brake systems may reach extreme temperatures brake fluid must have the ability to withstand these temperatures and not degrade rapidly.
SILICONE BASED FLUID
Fluids containing Silicone are generally used in military type vehicles and because Silicone based fluids will not damage painted surfaces they are also somewhat common in show cars.
Silicone-based fluids are regarded as DOT 5 fluids. They are highly compressible and can give the driver a feeling of a spongy pedal. The higher the brake system temperature the more the compressibility of the fluid and this increases the feeling of a spongy pedal.
Silicone based fluids are non-hydroscopic meaning that they will not absorb or mix with water. When water is present in the brake system it will create a water/fluid/water/fluid situation. Because water boils at approximately 212º F, the ability of the brake system to operate correctly decreases, and the steam created from boiling water adds air to the system. It is important to remember that water may be present in any brake system. Therefore silicone brake fluid lacks the ability to deal with moisture and will dramatically decrease a brake systems performance.
POLYGLYCOL ETHER BASED FLUIDS
Fluids containing Poly glycol ethers are regarded as DOT 3, 4, and DOT 5.1. These type fluids are hydroscopic meaning they have an ability to mix with water and still perform adequately. However, water will drastically reduce the boiling point of fluid. In a passenger car this is not an issue. In a racecar it is a major issue because as the boiling point decreases the performance ability of the fluid also decreases.
Poly glycol type fluids are 2 times less compressible than silicone type fluids, even when heated. Less compressibility of brake fluid will increase pedal feel. Changing fluid on a regular basis will greatly increase the performance of the brake system.
FLUID SPECIFICATIONS All brake fluids must meet federal standard #116. Under this standard is three Department of Transportation (DOT) minimal specifications for brake fluid. They are DOT 3, DOT 4, and DOT 5.1 (for fluids based with Polyalkylene Glycol Ether) and DOT 5 (for Silicone based fluids).
MINIMAL boiling points for these specifications are as follows:

Dry Boiling PointWet Boiling PointDOT 3401ºF284º F
DOT 4446º F311º FDOT 5500º F356º FDOT 5.1518º F375º F



Racing brake fluids always exceeds the DOT specifications for dry boiling points. Wet boiling points generally remain the same.
DOT 3 VS. DOT 4 and 5.1
AFCO's 570º brake fluid is a DOT 3 type fluid. However, it has a dry boiling point that is 52º higher than DOT 5.1 specifications, 124º higher than DOT 4 specifications and 169º higher than DOT 3 specifications. AFCO's 570º fluid meets or exceeds all DOT 3, 4, and 5.1 lubrication, corrosion protection and viscosity specifications.
AFCO's 570º racing fluid meets but does not exceed federal standards for wet boiling point specification; therefore, its classification is DOT 3. Because AFCO's 570º fluid is intended for use in racing type brake systems that undergo frequent fluid changes, exceeding federal standards for wet boiling points is of little concern. Racing brake fluids always exceeds the DOT specifications for dry boiling points. Wet boiling points generally remain the same.
WET VS. DRY BOILING POINT
The term boiling point when used regarding brake fluid means the temperatures that brake fluid will begin to boil.
WET BOILING POINT
The minimum temperatures that brake fluids will begin to boil when the brake system contains 3% water by volume of the system.
DRY BOILING POINT
The temperatures that brake fluid will boil with no water present in the system.
MOISTURE IN THE BRAKE SYSTEM
Water/moisture can be found in nearly all brake systems. Moisture enters the brake system in several ways. One of the more common ways is from using old or pre-opened fluid. Keep in mind, that brake fluid draws in moisture from the surrounding air. Tightly sealing brake fluid bottles and not storing them for long periods of time will help keep moisture out. When changing or bleeding brake fluid always replace master cylinder caps as soon as possible to prevent moisture from entering into the master cylinder. Condensation, (small moisture droplets) can form in lines and calipers. As caliper and line temperatures heat up and then cool repeatedly, condensation occurs, leaving behind an increase in moisture/water. Over time the moisture becomes trapped in the internal sections of calipers, lines, master cylinders, etc. When this water reaches 212º F the water turns to steam. Many times air in the brake system is a result of water that has turned to steam. The build up of steam will create air pressure in the system, sometimes to the point that enough pressure is created to push caliper pistons into the brake pad. This will create brake drag as the rotor and pads make contact and can also create more heat in the system. Diffusion is another way in that water/moisture may enter the system.
Diffusion occurs when over time moisture enters through rubber brake hoses. The use of hoses made from EPDM materials (Ethlene-Propylene-Diene-Materials) will reduce the amount of diffusion OR use steel braided brake hose with a non-rubber sleeve (usually Teflon) to greatly reduce the diffusion process.
THINGS TO REMEMBER
Brake fluids dry boiling point is more important then wet boiling point when used in a racing brake system.
Passenger cars very rarely will undergo a brake fluid change making the wet boiling point more important.
Racing brake system fluid is changed often and a system with fresh fluid will most likely not contain water.
Because of this, racers should be concerned with the dry boiling point.
Racing fluid exceeds DOT 3, 4, and 5.1 dry boiling point specifications.
Never use silicone based fluids in racing brake systems.
Using racing brake fluid will increase performance of the braking system.
Never reuse fluid. º Never mix types or brands of brake fluid.
Use smaller fluid containers that can be used quicker.
If fluid remains in container be sure to tightly seal and do not store for long periods of time.
Purge system (complete drain) and replace fluid often.
Immediately replace master cylinder reservoir cap following any maintenance.

seed

uh..haha..yea that makes no freakin sense i don't even remember typing that...must have been late..lol...but honestly i've never noticed in all my years two chambers inside there i just take the cap off and add to fill line

BlueXJ

Old style covers for the master cylinder had a large oval cover that allowed you to see everything inside the master cylinders. Newer ones just have a plastic resevoir on top that feeds both chambers. Guess you have never seen one of the older ones or torn one apart to rebuild it. Shows I am an old fart.

seed

ohhhhh...yea right you mean like the metal ones with the flippy thing,i haven't seen one of those since my 79 bronco guess i just forgot

moses

Try some Castrol LMA brake fluid. Its what high spped jaguars use. Its "LMA" Low moisture absorbant. buy four or five containers and start flushing the oil fluid out of the sysmtem, Make sure you bleed from the wheel cly that is the longest distance from the master cly. then end up finishing the caliper the is closest to the master good luck!

Stryder-Ryder

Thx all for the input. I will do a complete drain and fill and bleed with new fliud and keep and eye on things.