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

[jamesd]

Just reporting back on my findings. Thanks again WyrTwister for the awesome tips. Very helpful especially someone like me that is no too savvy on a/c work. I put some dye in the a/c system and saw a leak near the connectors on the compressor. I installed new o-rings and followed your advice. So far it's working great! It has been a week and so far no problems with brakes. Problem solved??? I wouldn't call it that just yet since the problem was intermittent and had no set pattern. But it looks promising so far. I did keep the old brake booster hose and did a little research with a hand vacuum pump. It turns out the valve would get stuck when vacuum was applied. Another words when I applied vacuum to the booster side, vacuum holds. Now when I apply vacuum to the intake side of the hose I got a vacuum! This just happened once and after that the valve operated normally without fail and air flowed freely. So my theory is.. if the valve wont open when vacuum is applied then that would cause the problem we've been having with loss of brakes. As I said I won't call this "problem solved" just yet. If the brakes works for a month without fail then it's fixed! I hope this information helps people who comes across this problem. I've done some Googling on this subject for a while and it seems like a common issue. Could this check valve not opening up as it should be the root cause of this? Hhhmmmm.. Was installing a new brake booster and master cylinder was a waste of money?? Well yes and no.. The car is 11 years old and I can rest easy knowing the car has all new brake system. Also I don't feel as bad knowing the GM tech did catch this either. Probably good for another 100k miles. Plus brakes is not something you want to skimp on either. If any one has any questions let me know. I will report back again if I find anything else.

[WyrTwister]

Happy if I was able to be of assistance .

Will keep our fingers crossed on the A/C & the brakes .

I would have never thought of the check valve being inside the vacuum hose . You are certainly right about the old check valve sticking intermittently . Not sure is that would be sticking open or sticking closed . But either way would not be good .

You are correct , with in excess of 100,000 miles , you are not hurt too bad by replacing the booster & master cylinder .

Happy you got the A/C blowing cool air .

I have used rubbing alcohol to clean off the dye from previous leaks . Then you can come back in a few weeks & examine it with the UV light and yellow glasses . The dye shows up even better if you examine it at night .

I have replaced a couple of A/C compressors that performed OK , but had leaks in the body of the compressor that I did not have the tooling / equipment to repair myself .

Hope you are over the hump with your list of things to repair on that car .

God bless
Wyr

[jamesd]

Thanks WyrTwister! I never thought about using alcohol. I've been using carb cleaner to clean it off. I will definitely do that plus way less expensive and car or brake cleaner lol.. Over all I spent $124 for brake booster, $60 for master cylinder and $90 for labor. Plus 5 bucks worth of vacuum hoses lol.. So far so good. I'm hoping to get the Aveo painted next month. We have a local Macco here where I live. Curious to find out how much they would charge for a full paint job.

[WyrTwister]

Cheapest to do a respray going back the same color .

I read that a respray , you can spend , almost the sky is the limit . Just depends on how good a paint job you want .

Please post what they quote you .

God bless
Wyr

[jamesd]

I have not gotten around to get a quote yet. It's on my to do list. So far brakes are working fine and no engine codes. Not sure what was all that about the vacuum leaks. But those codes have not returned back. Yay!

[WyrTwister]

Great to hear the brakes are good & the engine codes are gone !

Please refresh my memory . Did you say you replaced the duct / hose from the air cleaner box to the throttle body ? And the plastic thermostat & housing ? From what I read , those are common problems on the AVEO .

Best of luck ,
Wyr
God bless

[jamesd]

Well here is another update.. So far no brake problems what so ever. So... I am calling this SOLVED! Thanks for everyone's input!

[WyrTwister]

God bless
Wyr

[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?

[WyrTwister]

Best I remember , his vacuum hose to the booster has a check valve in the hose . New hose fixed the brake problem ?

God bless
Wyr