Combatcrayola

Hopefully someone will read this and point me in the right direction. I’m in the military currently stationed in Italy. I have a 2009, 45th Anniversary Edition GT with approximately 61,000 miles on it. About a month ago I was driving to work and noticed the brakes give way slightly. I thought it felt a little unusual but chalked it up to the ****ty Italian roadways. Over the course of the next week the brakes became spongy. I checked the fluid, it was okay and I saw no leaks on the lines. A week and a half later I thought I heard a scraping sound coming from the left front rotor and immediately ordered brake pads. The gear shifter started to become really hard to shift when the engine was running but not up to temperature. Once warm it was fine. A few days later the scraping became more pronounced and I realized it was the left rear rotor, not the front. I was fortunate to find some pads on the Italian economy (70 Euro) and replaced them. I didn’t plan on bleeding the brakes until I replaced the front pads that were due to arrive any day. I drove it for a few days and the brakes were still pretty spongy so I took it back to the auto craft center. Two hours later we had bled several air bubbles out but the brakes were still not building up pressure. I notice when I would initially apply pressure to the brakes they would hold briefly and slowly give way. If I tried them again immediately there was no pressure at all. After a few seconds there was an audible “pop” noise, like a valve opening, coming from the brake booster. After that noise I would have pressure again. After we bled all four brakes another mechanic looked it over and said the brake booster was probably bad. When I drove off I noticed the brakes were even worse now and at times, not responding at all. When I got home I did what any novice mechanic would do and “Googled” it. I looked up the symptoms of a bad brake booster; most said the brake pedal would be hard to push down. That’s not a problem with mine. That’s when I saw something about the slide pins. The slide pins were something I didn’t check at all. When I initially changed the rear pads a week ago I noticed the right side pads were worn evenly, but left outside pad was worn down much more than the inside. Additionally that outside pad looked like it was worn unevenly as well – like it was wearing diagonally. I’m doing the front brake tomorrow and will check the pins then. Are there any other suggestions?

SKAR

Make sure the pins arent seized as well as the calipers.

Combatcrayola

Okay thanks, I will check both. I'm sure the calipers are good ... that is, unless they are siezed in the open position.

Combatcrayola

Well FUDGE!!! Okay...new pads all the way around. System bled. Calipers are working and the slide pins are lubed and move easily.

Still no stopping power.

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petrock

That would indicate the caliper not sliding properly on the slide pins, or the outside brake pad is hanging up on the slide rails on the caliper mounting bracket.


Could be the brake booster or master cylinder. With the motor off, pump the brake pedal a bunch of times. It should get very hard after a few pumps. If not, then the master cylinder is bad or one or more of your flexible brake lines is ballooning from the pressure. You can test a brake booster with a hand vacuum pump. Also, with the car running, pull the vacuum hose to the brake booster and make sure you have good vacuum. If not, then you have a vacuum leak.

Good luck...

Combatcrayola

From what I understand, if it was the brake booster, I wouldn’t be able to push the pedal down, or it would be hard to. I pulled the vacuum hose off of the booster while the engine was running and there appeared to be a good vacuum. I checked all of the lines for leaks but not for ballooning. I’m leaning toward the master cylinder because of the audible “pop” noise I can hear. I’m thinking maybe there is an air pocket in it.

Combatcrayola

Anybody????

petrock

Test your theory by pulling the vacuum line from the break booster with the motor running and try to pump the brakes.


You’ve been given a bunch of things to check, including how to test the master cylinder and the ballooning brake lines. What were the results?

If you pop the hood and can pinpoint the master cylinder as the source of the popping sound, then it is bad.

blu30val

Usually a booster isn't associated with sinking, but maybe a faulty check valve can cause your problem, but I wouldn't think it'd sink lower than normal though. Either way I agree. Eliminate the booster and check again. Sounds like the masters bypassing to me honestly;but as you can tell, throwing parts at it isn't the best route to fixing it. Edit: there are parts behind master and booster that can bind and break but is very rare if you weren't messing with anything in there.

Combatcrayola

Thanks for the tips, help and advice. I think we've determined it is the master cylinder. I've never done one, soooo...now its at the shop. Looks like the total reapair (if it's only the MC) will run me about 230 Euro, parts, labor, and postage.

One of the pains of having an American car in Europe.

I'll let you know the results in about a week.