No brakes in the morning. It will definitely wake you up more than coffee.

[jamesd]

I recently bought a used 2005 Chevy Aveo LS 1.6 hatchback. I bought this car for my daughter to be driving to school and back. I just love this awesome car. It has 160,000 miles on it and it's been having this issue where sometimes (not all the time) it has no braking power. To me it felt like the brake booster gave out or the check valve gone bad. I had to use extra effort on the brake pedal to stop. But even then it just slowed. After going around the block braking power is restored. I check the vacuum hose to the brake booster and it was fine. I even went as far as discarding the hose clamp that it had at the booster and used a regular hose clamp with a screw in it. Three days later It did it again a second time so I bought a new AC Delco brake booster and replaced it myself. Everything worked fine for a week until this morning the problem is came back, same symptoms. So now I'm looking at the master cylinder. I did discover last Saturday that on the driver side front wheel I did saw a leak where the hose connects to the steel brake lines. It looked wet and around the connection. I just tightened the nut a bit more and hosed it down with break cleaner and hasn't leaked since. This was addressed before this no brake issue appeared this morning. I've also replaced the rotors and brake pads because the rotors were warped and had a pulsating feeling whenever I brake. All is good now. As for the no braking in the mornings is there anything I need to check for? Also what brands of MC do you all recommend? Doorman brand?

Thanks!

[avguy]

Did you bleed the system after repairing the leak? If not, I'd suspect that air was pulled into the line and naturally is still there.

[slayerized6]

Flush and bleed the system. You most likely have air in the brake lines or ABS block (if equipped). Check the cylinder seals on the brake calipers as well and make sure they are not compromised either.

[jamesd]

Thank avguy and slayerized6! I failed to bleed the system. I will definitely do a flush and a bleed. Plus it gives me an excuse to buy a mityvac hand pump too! Also the brake fluid in the reservoir has a coffee color to it so yeah it definitely needs some tender loving care. Ok maybe i'm exaggerating the color of the fluid but it's definitely slightly darkish. Oh also my car does not have ABS. Sorry that I omitted that part. Thanks!

[xintersecty]

speaking of hand pumps. Here is a consideration
http://www.aveoforum.com/forum/f94/u...-review-16303/

[jamesd]

speaking of hand pumps. Here is a consideration
http://www.aveoforum.com/forum/f94/u...-review-16303/

Thanks for the tip! Just wondering how big is your air compressor? I have a Harbor Freight 8 gallon one. Would that be enough to power the tool?

[xintersecty]

Thanks for the tip! Just wondering how big is your air compressor? I have a Harbor Freight 8 gallon one. Would that be enough to power the tool?

I used a 2 gallon pancake, it was more than ample to do the job.

[jamesd]

Thanks xintersecty! I will definitely look into getting. I looked for one at my local store HB but they ran out. Ill check again later this week. I tried to do the bleed and no problems for a week. Then one afternoon after the car being parked all day it did it again. This time tho as I backed out I applied the brakes and it braked then.. it let go like I had no brakes and within 4 seconds the brakes came back alive again with no problem. Worked all day. So.. I took it to the dealer and I spoke with the tech that is working on it and he was puzzled as well by my situation. They will do a break bleed again and see what happens. He told me if it was air in the lines the problem will be there all the time. Not just every now and then. It feels like its a vacuum leak or something but it's a brand new booster. Booster hose is fine too. EGR valve maybe???

[jamesd]

Ok.. the jury is in... They are saying it needs a new master cylinder. I will buy it at Autozone and have them install it.

[rootbeer]

HO Ho-So I am not losing my mind after all. I have a 2004 aveo 5 speed with same problem. At random times, I go to stop the car and the pedal is rock hard. Feels exactly like the master vac. has failed. Car is running smoothly, it's not like there is a huge vacuum leak. After a couple minutes, brakes work fine. Usually happens in the morning, just a few minutes into my drive to work. This has happened 6 ~ 10 times in past year. I am ready for it now, I am ready to stand on the brake pedal if need be. Will not let my wife or kids drive the car because of this. So what gives?