My mother’s in low has a problem with brakes that so far no one can tell what is wrong. The problem with her brakes some times appear and most of the time the brakes are fine. In very low speed ( forward or backing) when she press the brake pedal to stop, the pedal sink and the car keep going without stopping. The local auto-mechanic replaced something ( she does not know) and didn’t fix the problem, then they replaced the main cylinder and still have the problem. She went to the dealer and the dealer decide that the brakes wasn’t bled properly so the dealer bled the brakes. The car work fine for a wile until the problem appear again. Does anybody has an idea what is going on with thous brakes?
This sounds like a bad master Cylinder, but you said that was replaced. Next I would see if 1 of the 3 rubber lines was bubbled and swelling. Also, I would check all componets for leaks.
It’s possible that the mechanic didn’t bench bleed the master cylinder prior to installing it.
When installing an MC, it’s good practice to run a tube from the output ports to the reservoirs and pump the reservoirs, which should be repeatedly filled. That pushes the air out of the MC chambers and various paths within and purges the MC before installing. Not doing so means that the air in the MC has to then work its way through the brake lines and calipers, and then the system needs to be bled, sometimes repeatedly, to remove it.
Does pumping the pedal make the pedal feel much harder? That’s a good sign that there’s still air in there working its way out.
If the dealer bled the brakes, a pressure bleeder would have been used. And this should have removed any air in the brake system.
If you’re saying the brakes were fine for a while after the dealer bled the brakes, and they slowly got worse, then there may be a caliper piston seal that’s allowing air into the caliper each time the brake pedal is released.
I’ve seen this happen on many vehicles, and it leaves mechanics scratching their heads.
Tester
If pumping the pedal when there are no brakes doesn’t help bring them somewhat back, I’d have the ABS unit checked. It may be failing.
The local mechanic replaced the master cyonder and the brakes worked good for a wile and then the car has been checked many times until they give up. The dealer checked the car and said "wasn’t bled " so they did. Worked good for a wile.
And YES it get beer when you pump the pedal, then the car is working good for wile.
It happens only in very low speed like under 10 MPH and the problem is not consistent.
I just found out that another person had the same problem with 2008 model that his car did not stop and entered intersection wich caused accident and the car was totaled.
Given that local efforts, including by the dealer, have not resolved the issue, look in the owners manual to see how to contact Buick corporation and follow those instructions. They may have one of their regional troubleshooters get on the case. You can also contact the NHTSA or visit their website to see if they have similar reports in their records.
Taking into account what was replaced thus far and the result in braking. You stated the brakes were fine for a while after the master cyl replacement…then returned to this state. There can be several causes for your issue. From a fluid leak, ballooning rubber lines to the E brake.
You need to look on the ground and on the inside of the wheels for fluid or a wet look…or outright dripping on the ground. If the system was fine after the master replacement it means it was bench bled properly and installed correctly…if it then got mushy later on…it can be from fluid loss somewhere. or an E Brake not adjusting properly.
Ballooning brake lines would never have allowed a firm pedal from the get go… But are a possibility at a later time and or after the pedal was once firm and proper again as in this instance.
I would look for a leak as a very first step in this case though…Seems the most probable…followed by ballooning rubber brake lines. Ballooning fools a lot of so called mechanics…as if they cannot fathom the possibility…so they ignore it completely. Shame…Ballooning is very very real.
Back to a brake fluid leak that fools “mechanics” the disc caliper can leak fluid into its piston dust boot for quite some time and cause air in the system …and mushy pedal…AND not spill a drop of brake fluid instantly…it will eventually for sure…but it is slow enough to fool people. Simply check behind the dust boots on the calipers…sometimes you get a nasty surprise
Blackbird
The local mechanic said that they Chek port leaks many times and didn’t find.
The hardest part is to understand why the problem appear only at very low speed of the car and not consistent, you don’t know when will happen.
Thank you guys for the effort you put, I will past your suggestions.
I’m assuming there’s no check engine light or abs light or anything unusual on the dashboard warning lights. And that all the dash warning lights work with the key in “on” but the engine not started. And that the abs unit has been checked for diagnostic codes. All that is the first place to start, if it hasn’t yet been done.
If air is re-entering the system as suggested above it is possible for a shop to verify that. The way a diyer’ would do that is by connecting a clear plastic tube and bleeding each wheel one by one. Air bubbles that re-entered the system will show up. Shops may have better ways to do it.
Another idea, the brake power booster could be bad. Shops have a procedure to check those.
If all else fails, you could just have all the brake components replaced. New rubber hoses, calipers, pads, and rotors all around. After all, it isn’t safe to drive the car the way it is. So the car is now just taking up space. I’m assuming nobody’s driving it, right? Ask your shop how much that work would cost, it might not be as expensive as you think. Cheaper than buying a replacement car certainly.
Thats insane… Bring the vehicle to a good independent mechanic so he can spend some time with it… This is not a hard issue to figure out to be honest. Do not replace everything that would be illogical at best… Leaks or air in the lines is rather simple to figure out…it may take some time… Brake bleeding must also include the ABS block as well…The ABS pump needs to be run to purge air from it. I have a computer interface on VW and Audi where I can trigger the ABS pump while bleeding the system…Im sure there is something similar here and should be done to call the system “bled properly”
Blackbird
The car has been to a local shop and the dealer already. It seems sort of like grasping for straws to say to take it to yet another shop. But maybe that’s the best advice. It must be a very frustrating experience for the OP.
When 3 idiots look at your car…where did you get? I mentioned before…Im the guy who gets the cars that 2 dealership trips and 1 independent shop cannot figure out.
Its not the problems are difficult so much as that it takes a little while to live with the vehicle to see what it is really trying to tell you… Most shops or dealers simply do NOT invest the time…as time is money to them. Hey Im all for it…bring it to incompetents first by all means… I can fix it…I promise…and I do. lol
Blackbird
US NHTSA CAMPAIGN ID: 05V156000
Mfg’s Report Date: 04/19/2005
Component: SERVICE BRAKES, HYDRAULIC:PEDALS AND LINKAGES
Potential Number Of Units Affected: 61594
Summary:
ON CERTAIN PASSENGER VEHICLES, THE CLIP THAT SECURES THE BRAKE PUSHROD TO THE BRAKE PEDAL ARM PIN COULD HAVE BEEN BENT WHEN IT WAS INSTALLED. A BENT CLIP MAY COME OFF, ALLOWING THE BRAKE BOOSTER PUSHROD TO SEPARATE FROM THE BRAKE PEDAL.
Consequence:
PUSHING ON THE PEDAL WILL NOT APPLY THE BRAKES AND A VEHICLE CRASH COULD OCCUR WITHOUT PRIOR WARNING.
I’d go back and read Tester’s comment. It seems to fit the scenario of having good brakes after they are bled but then gradually needing to be bled again. So air is being introduced, correct?
If this only happens after the car has been driven for awhile, then I’d suggest the son in law follow the mother in law around when she is driving. He might see the problem.
Just a guess, the OP’s command of the English language seems to be a little on the short side. Do you suppose he’s posting from a third world country where dealer service/knowledge is also lacking? Indy shops would only be worse.
Reading that report above…the info in that document could surely explain why he has normal brakes and pedal feel and then all of a sudden NOT again…and then it gets better afterwards…then fails again.
If the Booster Cylinder / Brake pedal rod was not properly “in situ” and can flop out of place and then back into place… we definitely have something to look into…
Giving advice here when the OP does NOT do the work themselves is kind of a little hopeless…An issue like this is going to take some hands on and some troubleshooting over time…relying on questionable shops that want a Silver Bullet type of repair…is really not going to help much…unless they get lucky. Shame…
Blackbird
Let me clarify my earlier post. Yesterday I was behind an Escalade whose brake lights were on almost all the time, even when accelerating away from a stoplight and at speeds up to 60 mph. Occasionally they would go off so I knew it wasn’t a defect in the brakes.
^
Several years ago, I happened to be driving in back of a co-worker who was operating her new Volvo wagon. After noticing that her brake lights were “on” about 90% of the time, I tried to be helpful by suggesting that she take her new car back to the dealership for replacement of the brake light switch. She thanked me, although she looked a bit confused.
A couple of days later, she told me that she mentioned my suggestion to her husband, but after taking him for a ride in her new Volvo, he pointed out to her that she was resting her left foot on the brake pedal most of the time. With somewhat of a red face, she admitted that she had never previously been aware that she did this type of thing, and that if not for my intervention, she might not have been aware enough to stop doing it.