2007 Civic Brake Reservoir Cap Swollen

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Replaced the previously swollen rubber diaphragm belonging to the brake reservoir cap a few months ago and the rubber diaphragm is once again swollen. I flushed and replaced the brake fluid the same day I replaced the diaphragm. What would cause the rubber diaphragm to swell up again? The fluid looks clear but I was thinking about testing the brake fluid with the litmus paper test kit.../ Any advice greatly appreciated.
 
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rubber diaphram shouldn't swell up if the fluid is of proper type and not contaminated. If contaminated (with oil), brake-related rubber diaphram will becomes swollen. Q.
 

Gito

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how could it be contaminated with oil? Is a swollen diaphragm a standard indicator for checking contaminated fluid? I thought that a brake fluid test kit would be accurate.. Please advise
 
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Its tough to say without seeing it. I have seen this from oil contamination, it was swollen badly and for lack of a better word soggy. It is not normal. Are you cleaning the cap with brake cleaner or something before putting it back on maybe? I really hate to post this without seeing it, its hard not to sound like an alarmist but the issue is very serious. It could be just a cheap rubber they used, where did you get it? Is it a HELP part from a store or a dealer item? Can you post a picture of this, if it is oil contamination you have serious problems and the car is dangerous, it can suffer complete brake failure at any time.
 
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Listen to what Trav posts. As I've mentioned elsewhere, I've seen them distended as brake pad material wears and fluid goes down, but actual swelling is not a good thing. And, having grown up on a farm, I've seen containers, including brake fluid containers, being reused in ways they should not be, such as holding motor oil or gear oil or transmission fluid.
 

Gito

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This is a 2007 Honda Civic. Brake fluid was dirty when I changed it. I bled the fluid unit it came out clear. No oils or any other fluids other than brake fluid was poured into the reservoir. Swollen reservoir cap diaphragms is something new to me. I own a 91 Honda Civic that does not have that rubber diaphragm. Again fluid is clear compared to what was flushed out. The rubber diaphragm was purchased at the dealer. How can a rubber diaphragm be used as an indicator for brake failure? Are we talking about the same thing here. The brake reservoir has a cap and under that screw on cap is a rubber diaphragm which fits perfectly. The diaphragm now has expanded to the point that the reservoir cap can no longer be screwed on WITH the diaphragm in place. I cannot upload pictures on this website but I will try to upload a picture or two on to shutter fly and then attach the link here
 
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Originally Posted By: Gito
How can a rubber diaphragm be used as an indicator for brake failure?
Easy, it is made from the same type of rubber used in the whole brake system. If its swelling then the other rubber components are also. The swollen rubber may no longer has the strength to seal under pressure and cause leaks or worse a complete blow out, binding and all sorts of problems. EPR, EPDM rubber is used in brake systems and cooling system hose (antifreeze is close to Dot 3-4 brake fluid), it resist glycols and esters very well but not oils. PS fluid, engine oils, mineral oils (unless its a Citroen, different rubber), etc. Some makers of PS fluid and a brake fluid puts them in almost the same bottle. It wouldn't be the first time, it got mixed up by mistake. Not saying you did just throwing a possibility out there.
 

Gito

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Recap: Brake fluid had not been replaced for approximately 200,000 miles. Brake fluid was replaced for the first time 2 months ago. Two months later, brake fluid again contaminated Update: The swollen brake reservoir cap (rubber diaphragm) was, in our case, a good indicator that there was a problem. I have read, but have NOT confirmed, that the pump brake pedal bleeding method exposes existing problems with Master Cylinders vs. using gravity, pressure or vacuum bleeders. We replaced the Master Cylinder and didn't want to deal with any other hidden issue. Just the thought of not replacing the brake fluid for 200,00 miles was enough to scare my buddy. Fresh new start. Will report back in a few months to update any changes to the brake reservoir rubber diaphragm. Thanks for everyones input
 
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Originally Posted By: Gito
Recap: Brake fluid had not been replaced for approximately 200,000 miles. Brake fluid was replaced for the first time 2 months ago. Two months later, brake fluid again contaminated Update: The swollen brake reservoir cap (rubber diaphragm) was, in our case, a good indicator that there was a problem. I have read, but have NOT confirmed, that the pump brake pedal bleeding method exposes existing problems with Master Cylinders vs. using gravity, pressure or vacuum bleeders. We replaced the Master Cylinder and didn't want to deal with any other hidden issue. Just the thought of not replacing the brake fluid for 200,00 miles was enough to scare my buddy. Fresh new start. Will report back in a few months to update any changes to the brake reservoir rubber diaphragm. Thanks for everyones input
I wonder if using lots of brake cleaner to clean the area around the reservoir and the cap itself (common practice), would cause the rubber cap to swell. Brake Cleaner is petroleum based and can do weird things to rubber.
 

Gito

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All we did was to clean the outside of the reservoir with a rag while the cap was ON
 
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