chevy truck brake problems (mc or booster)

[tonynew]

I have a 2007 Chevy crew cab classic. For some reason I keep loosing fluid but I don't have any leaks anywhere. Need to know if it's my master cylinder going out or my brake booster. I have had this problem before but it was in a 77 Camaro. Can some please tell me how to diagnose or if im even looking in the right direction.

 

[JCH13]

If you're losing brake fluid, but don't know where it's going, there's a good chance it's leaking from the MC into the booster.

Try a couple things:

Park over some dry pavement, with your truck running, and pump the brakes until a good amount of fluid has disappeared. Then check the ground for leaks.

Pull the MC off of the booster and see if there is any fluid present at the junction there, or any leaking out of the MC front seal.

Good luck n00b

 

[tonynew]

Yeah ive pulled the calipers and drums and there isnt any leaks there or in my lines anywhere, now if my mc is leaking into the booster does that mean i need to replace both of them or will my booster still be ok.

 

[NutBucket]

Booster should be fine. I would try the MC first.

EDIT: Just for clarity if the booster was bad you'd either have symptoms of large vacuum leak and/or a VERY hard brake pedal.

 

[manimal]

Booster should be fine. I would try the MC first.

this


welcome new guy!

 

[tonynew]

Thanks guys, im gonna try it out. Ill post back once i find out more. New question how safe is it to drive while it is doing this? Im in fresno ca and supposed to be making a trip up to santa cruz ca tonight. Should i chance it or no?

 

[SparkyJJO]

Uhhh brakes are awfully important. I wouldn't want to drive a vehicle with questionable brakes.

 

[tonynew]

It's not that they don't work They work fine, im just having to refill fluid every couple weeks.

 

[SparkyJJO]

If it has been consistent like that then ok. I was under the impression is was leaking pretty good.

Fix it soon tho. Brake fluid will destroy the innards of the booster if it is getting in there.

You did check your cap, right? My brother's Escape had a bad cap seal.

 

[Zenmervolt]

It's not that they don't work They work fine, im just having to refill fluid every couple weeks.

If the master cylinder fails the rest of the way, you'll have no brakes. It's rather important. If the fluid level gets too low and you pull some air into the brake line you'll lose a lot of effectiveness.

Now, granted, it's not terribly likely that the MC would fail catastrophically in the next few days, but it's still a definite risk.

ZV

 

[tonynew]

I did replace the cap and seal recently but thats only because i lost the stock one. Im not getting any fluid coming out there though, i check regularly.

 

[Raizinman]

Booster should be fine. I would try the MC first.

EDIT: Just for clarity if the booster was bad you'd either have symptoms of large vacuum leak and/or a VERY hard brake pedal.

Way too much work.

Instead, remove the vacuum hose from the brake booster. If it was leaking, the inside of the hose will be wet and probably dripping with brake fluid.

Most likely you will need both the MC and brake booster, as when brake fluid contaminates the rubber in the booster, it will weaken and ruin it. Replacing both is the only answer.

 

[tonynew]

Just pulled the Jose off the booster and there's no fluid there but it's also on the top side or should I say above where the MC is connected to.the booster. I don't know if that makes sense. It would have to be pretty full of fluid to be getting fluid up that high or will the pressure in the booster push the fluid up there. I honestly don't know how or what the innards of the booster work.

 

[Raizinman]

Just pulled the Jose off the booster and there's no fluid there but it's also on the top side or should I say above where the MC is connected to.the booster. I don't know if that makes sense. It would have to be pretty full of fluid to be getting fluid up that high or will the pressure in the booster push the fluid up there. I honestly don't know how or what the innards of the booster work.

The engine vacuum would pull some fluid into the hose and engine. If bad, the inside of the hose would be wet.

I would next take a flashlight and crawl down under the car and look at the tire sidewalls of the tires (facing the inside of the car) and also the rear backing plates and front calipers for leakage. Often the inner side walls of the tires will be brake fluid stained from leakage. Often you can see the brake fluid flung on the inner fenders, so look there too.

 

[Mikesc1006]

I'm not sure how forums work have never done this so bare with me please I have an 86 silverado that is giving me issues with the brakes replaced booster and master cylinder bench bled the MC new wheel cylinders and lines calipers working properly but still getting no brakes plus I bled all of them in the proper order, rear cylinders not getting much pressure thank u for any help and info if anyone can

Hello. Welcome to AnandTech forums. This particular thread is over a year old; the most recent reply was in January of 2013. Adding a new reply to such an old thread is generally frowned upon as it is unlikely to help the original poster ("OP") and even if you have a new question of your own, people tend to see the OP's question first and respond to that (if they don't notice the date and ignore the thread completely). The best way to get an answer to a question you have is to create a new thread for your question. While I have closed this thread, please do not hesitate to create a thread of your own for the issue you are having with your particular truck.

Cheers!

Zenmervolt - AnandTech Moderator