Brake Reservoir cap

[xtmsports]

Hey guys, I've been having problems with my brakes and pressure bleeding. You guys have helped out tremendously!

I finally got everything bled and running good...for about a day and now it seems to be back, spongy air in the brake system causing one caliper to grab more than the other three. I have replaced all four calipers.

I just noticed that my brake reservoir cap has a rubber seal under the cap and that a big chunk is missing.(size of half a dime)

I was wondering how important is this piece of rubber? Does it really provide an air tight seal? Maybe that gap is allowing air into the system and causing my brakes to improperly brake?

Thanks in advance!

[shogun]

Copied from another page: The brake system uses a glycol-based hydraulic fluid. The fluid is "hygroscopic," which means it tends to absorb moisture over time (never leave a can of brake fluid open for this reason). Moisture lowers the boiling point of the fluid and causes internal corrosion in the brake system. That’s why the fluid should be replaced when brake repairs are made or every two years for preventive maintenance. There are several different types, based on the boiling temperature and other characteristics of the fluid. DOT 3 or DOT 4 is used in most passenger cars and light trucks. Use only the type of fluid specified by the vehicle manufacturer. Using DOT 3 in an application that calls for DOT 4 might create a safety hazard. DOT 5 brake fluid is different from DOT 3 and DOT 4 in that it is silicone-based. DOT 5 is NOT recommended for any vehicle equipped with antilock brakes - but it can provide long-lasting protection against corrosion for vehicles that are stored for long periods of time or are driven in wet environments.

[xtmsports]

Copied from another page: The brake system uses a glycol-based hydraulic fluid. The fluid is "hygroscopic," which means it tends to absorb moisture over time (never leave a can of brake fluid open for this reason). Moisture lowers the boiling point of the fluid and causes internal corrosion in the brake system. That’s why the fluid should be replaced when brake repairs are made or every two years for preventive maintenance. There are several different types, based on the boiling temperature and other characteristics of the fluid. DOT 3 or DOT 4 is used in most passenger cars and light trucks. Use only the type of fluid specified by the vehicle manufacturer. Using DOT 3 in an application that calls for DOT 4 might create a safety hazard. DOT 5 brake fluid is different from DOT 3 and DOT 4 in that it is silicone-based. DOT 5 is NOT recommended for any vehicle equipped with antilock brakes - but it can provide long-lasting protection against corrosion for vehicles that are stored for long periods of time or are driven in wet environments.

From the article, sounds like air is not good. However, will brake performance drastically decrease if the cap seal is somewhat missing a chunk? I assume that since its missing a chunk, that its not 100% air tight. But is that enough to notice a decrease in braking?

[632 Regal]

hmmm, that really sucks. Mine dont have a gasket there at all, no wonder its always messy around that thing. Guess Ill score a gasket and flush that puppy again.

[xtmsports]

hmmm, that really sucks. Mine dont have a gasket there at all, no wonder its always messy around that thing. Guess Ill score a gasket and flush that puppy again.

I take it that since your's doesn't have a rubber seal, then its not that important to brake operation?

[genphreak]

Maybe even $1 (can't remember).

They stop ur brake fluid picking up water- it prevents hot, moist air going in to the resovoir during the day and precipitating into the brake fluid when it cools down at night.

This over time will put water in yoru brake lines... yuk.

My seal was dying so I bought a new one with some other stuff from www.eap4parts.com recently, went on in 2 secs.

GP