Hey Guys, Merry Christmas!!!
I was at my family Christmas party last night when I got sent out to meijer (a Michigan grocery and general merchandise store) to pick up a few things. Driving through the parking spot with my little cousin in the passenger seat, I hit the brakes approaching a parking spot, and the brake pedal fell out from beneath my foot and went almost all the way down. The emergency brake light came on. I pumped the brakes a bit and got a little bit of pressure back, but the pedal that had been high and firm (thanks to 2 new calipers, 4 ceramic pads, and bleeding all the way around) had dropped most of its height and firmness. After parking, I checked my brake fluid level, and it was quite low, but there was still some fluid in the reservoir. It was below minimum level. I bought some fluid at meijer and filled it up. No noticeable change. I carefully drove it home on what brake pressure I had left.

It's probably just a coincidence, but I will also mention that my engine later overheated that day, too. I think that's a totally separate cooling system problem though, and it's just coincidence and terrible luck that they happened on the same day. I will mention though that yesterday was just 3 degrees where I live. My first thought was that in part because of the cold, one of my old, brittle 14-year-old brake lines ruptured under pressure. Whatever the cause, I'm very lucky that it didn't happen while driving at a higher rate of speed. My airbag light is on, so that would have been a bad accident. Anyway, here's the link to the thread I made about the overheating. https://blazerforum.com/forum/engine...21/#post612665

I talked to my uncle about it just to bounce ideas off of someone, and he said it could be that my brake pads got so worn that the master cylinder sucked in air because all the fluid was being used to push the brake pistons so far in. I don't think that's the case, because I just put new brakes on this summer. The only way they would be worn already with the low amount of driving I do is if one of my calipers is worn so badly that the piston constantly presses one or both pads against the rotor. It's possible, but it's more possible (and would partially explain my crappy 16.5mpg I've been getting lately ) to be something else like a ruptured line or even a bad master cylinder I suppose. I have a crappy ABS code reader, so I'll use that on the car tomorrow if I end up by my girlfriend's place. It'll probably just give me a stupid obvious code telling me that the brake power and fluid are low. Let me know what you think it could be. It's driving me nuts having my car be so sick and stuck helplessly at my girlfriend's place where I can't make it better.

However, with the amount of troubles this car has, the amount of work I keep putting into it only to have another problem arise, the ABS not functioning, the airbag not functioning, and 16.5mpg in a car with a weeeak 190 horsepower (and that was 200k ago), I will likely be getting a new car if I get the job I'm hoping to soon. I had been hoping not to, because I wanted to hang on to this, but if it's not reliable, keeps breaking, and I can't trust it to protect me in an accident, then I will have to replace it. I fix at least 2 problems a month, and 3 more come up. I feel like I'm constantly working online and in the garage on this car to keep it alive. I feel like I'm beating a dead horse, one that only gets 16.5mpg . . .

Anyway, let me know what you think it could be.

 

If you keep losing brake fluid, yes, you probably have a leaky line or wheel cylinder. If the fluid level hasn't changed much, your master cylinder may be on its way out.

 

If you didn't have this problem beforehand, check for drop spots. Kinked line, crossed threads, the rubber gasket on top of the reservoir. Every stupid thing you can think of... check it because it's better than throwing an expensive new part at it and thinking it'll fix the problem.

 

I was able to drive the car home from my girlfriend's this weekend because I fixed the cooling system. However, the brakes are still screwed. Lots of air in the system. I filled the brake fluid reservoir before I left my girlfriends, and the reservoir was half empty by the time I got home, about 30-40 minutes away, a straight shot with not much braking.

I might have to do something with the Jimmy that I haven't done in a long time. . .take it in. I can't see any dripping either, and I don't think it's crossed threads, because I haven't worked on the brakes since summer. I'm no good at diagnosing problems with brakes, but I did use my ABS code reader and pulled 5 codes. The ones for the driver's front wheel speed sensor are pre-existing. I even replaced the sensor and it still didn't go away.
The codes are:
C0226 - Left Front Wheel Speed Signal Missing
C0227 - Left Front Wheel Speed Signal Erratic
CO225 - Left Front Wheel Speed Sensor Circuit Open
CO265 - EBCM Relay Circuit
CO223 - Right Front Wheel Speed Signal Erratic

Would the CO265 code be responsible for this? I can't see how, as I'm losing fluid somewhere, so no right?

 

Well, Here's your 265.
Being most of your issues are in the left front, which is the closest to the master cylinder, could be why you're losing brake fluid. How does the bay look underneath the reservoir tank? Have you jacked up the left front with the tire off and pumped the brakes? The last 3 on the list don't seem like they'd have uch to do with losing fluid.

Codes only get thrown because of an irregular voltage, and this one happens to be reading low. Theres are 6 valves solenoids and one master pump. I haven't dealt with this personally, but if I can help rule one thing out, you're one step closer to isolating the problem.

 

Look for a line or hose that is damp. If you've been around dust there may be a dust build up.

Now, something I haven't seen very often, but can happen is a failed master cylinder along with a leaky power booster. I can only think of three times I've seen this in 40 years of brake work. The seal around the brake pedal shaft leaks and the slight vacuum leak will suck it into the intake and burn it. Like I said before, this is really, really rare.

I'm thinking you may have a bad wheel cylinder. This will show up as streaks of wetness on the affected tire.

 

Fine idea, but very hard to do in this weather. My area just got hit by a snowstorm. EVERYTHING is damp, cold, and frozen. There's no dust buildup anywhere because the roads are covered in snow. Pulling wheels off tomorrow. What should I look for with the wheels off?

 

you can have someone just get in the truck and pump the brakes while you lay underneath it. i actually just looked at a 2000 grand voyager that has 4 leaking brake lines and the brakes are actually pretty decent...

another thing you can check if you dont think you have a blown line is sometimes the back of the master cylinder will blow out causeing all the fluid to go into the brake booster. easy way to check is unplug the big vacuum line going to it and stick something long and bendy into the hole, like a zip tie. if it comes back out with brake fluid on it then theres your problem.

 

If you have rear drum brakes, when you take the wheel off, the drum will slide right off too. Unless you have a gouged drum. When you pull it, look at the wheel cylinder. It should be dry. If it looks wet, it's leaking. If it's leaking really bad, the whole brake shoe assembly will be soaked with it and the tire will have streaks of it. Laying the wheel face down and looking at the back side of the tire and it will look like it's spraying out of the tire. It's actually from the drum.

 

to the last few posters, the 2000 gmc jimmy has rotors on all four wheels, so there are no rear drum brakes. I am going to try to take a closer look at the brake lines with the wheels off, but honestly that might be a waste of time because I wont know what to look for, and even if something is leaking brake fluid, it will be impossible to tell because everything is wet, frozen, and snow covered where I live right now. I might just replace my pitman arm (did the idler last month) and take the car in for an alignment and ask them to take a look for any leaks while they have it up there.