[hr]Well my front pads wore out on my Concorde. No problem...so i thought......went down and bought a new set went home to replace the pads...which I did! I have done many brake jobs over the year and never thought about this car having ABS...well I pushed the calipers closed with a C-clamp like always had...never even thinking an ABS car maybe different! Well when I got in the car to pump up the brakes the pedel sure enough pumped back up no porblem but then i started the car. The pedal went very soft and now will slowly sink to the floor. Well I though I couldnt have got air in the system but I tried bleeding the brakes anyway...still the same. So them I called the idiots that work at my Napa store and they all said oh yeah you cant force pressure back throught newer cars ABS systems ..."It will take out the master cylinder"... they said!
I thought that sounds strange and I asked why...Why would forcing fluid back in to the Master cylinder cause any problem...They didnt have answer...so I took that for fact....so need less to say he sold me the master cylinder...I went home bench bleeded it good...installed it....bleed all the brakes...nice solid pedal now...start the car...slowing shinking to the floor....no change....so now I pissed! Now I go to the handy dandy internet to find it posted all over....dont push pressure back though ABS system because it has the potential to cause problems with the ABS units....NOT THE MASTER CYLINDER! Im feeling a bit stupid now...should have went here in the first place! So now im here asking what next? I have never bleed a ABS unit and I looked at it and i dont see where the bleeder is. Can anyone here give me some advise...is the ABS unit screwed up because of this?

 

humm I have never seen such a mess I use c clamps and brake caliper tools all day long on everything up to 07 stuff. Been doing it for 10 years on Chryslers and myslef owns a 98 Concorde. Lets look at this in a different way here U have a soft pedel right?? can u pump it up and holds pressure when the car is not on?? if so u dont have anything wrong with the mechanical part. Check the vac booster u could have poped a hole in it if u pressed to hard and fast from the pressure back into the master cyl. The abs only works when the sensors tell it to thats it u dont even use the abs unles u are having a lockup prob. If u have a vac guage that would be the sure fire way of seeing if u have a vac leak inside the booster torn boot. Easy to replace from what u can see i am sure.. Let me know
kevin

 

Kevin,
Yes it appears that the booster may be the problem but im not sure. First off…..I had check the booster when I first figured out I had a problem....it appeared to hold pressure. At the time I check it I pulled a vacuum of 16 hg and let it sit for a minute and it held with no apparent leakage. So I thought the booster was fine. After your post I went to check it again…so I pulled a vacuum of 16 hg again but I tried to pull it a little higher and it wouldn’t. I pumped and pumped and couldn’t get any more vacuum then 16 hg. I thought that was strange and if I pushed the brake peddle it lost about 6 hg which I believe is about normal but if I tried to pull the vacuum back up to 16 hg again it wouldn’tchange from where it had dropped too. I pumped and pumped and it would just stay at 10 hg now. I pushed the brake peddle until the gage said there was no vacuum. Then I tried to pump it back up and it would not hold any pressure at all. So then I plugged the spud for the booster vacuum...deactivating the booster...started the car...pushed on the brakes and it stayed solid.....if I hook the booster up the brake peddle was back to sinking to the floor again....so is my booster bad? I feel that it is but Im a bit confused as to way it will not hold a vacuum but after pumping the brake pedal bleeding off the pressure then it will not. If I run the car and test the booster again it will hold a vacuum right off (16 hg only again) but if I pump the brake peddleto bleed off the pressure it will not hold any vacuum at all no matter how many times I pump. What do you think?
Thanks for you help!

 

the vac is supplied all the time its not just a one time shot of vac its hooked right up to the manafold for engine vac all the time. here is the idea behind teh booster



POWER BRAKE VACUUM BOOSTER The purpose of the vacuum operated power brake booster. Is to reduce the amount of force applied to the brake pedal by the drivers foot. To obtain the required hydraulic pressure in the brake system to stop the vehicle. For the 1998 M.Y., this vehicle utilizes a Bosch vacuum booster for all applications. The power brake booster can be identified if required, by the tag attached to the body of the booster assembly Power Brake Booster Identification This tag contains the following information. The production part number of the power booster assembly, the date it was built and who manufactured it. NOTE: The power brake booster assembly is not a repairable part and must be replaced as a complete unit if it is found to be faulty in any way. The power booster vacuum check valve is not repairable but can be replaced as an assembly. The power brake booster is vacuum operated. The vacuum is supplied from the intake manifold on the engine through the power brake booster check valve Power Brake Booster Assembly As the brake pedal is depressed, the power boosters input rod moves forward. This opens and closes valves in the power booster, creating a vacuum on one side of a diaphragm and allowing atmospheric pressure to enter on the other. This difference in pressure forces the output rod of the power booster out against the primary piston of the master cylinder. As the pistons in the master cylinder move forward this creates the hydraulic pressure in the brake system. Different engine combinations require different vacuum hose routings. The power brake booster assembly mounts on the engine side of the dash panel. It is externally connected to the brake system by an input push rod to the brake pedal. A vacuum line connects the power booster to the intake manifold. The master cylinder is bolted to the front of the power brake booster assembly.