brake pedal goes to floor unexplained

[burt ragio]

After installing stainless steel brake lines some time back I was expecting a firmer pedal. I thought I may have gotten air in the system. I gravity bled & pressure bled the system & still had the same results. The pedal with continous pressure would continue to sink to the floor while in park. So I had my ABS brake modual bled at a Lincoln Mercury auto dealer. The results are the same. I was informed this is normal with the Marauder Crown Vic Grand Marquie. The service mgr said that is the design. I want to know why the pedal continues to the floor under constant pressure while in park if there is no air in the system. Where does the fluid going ?

[jgc61sr2002]

IMO there is an internal leak in the Master cylinder.

[BAD MERC]

Not normal in my car. I would check for leaks. My pedal got firmer with the SS lines.

[Black_Noise]

IMO there is an internal leak in the Master cylinder.

there is eithe a leak, or there is a bypass valve that is releasing pressure in the master cyclinder, im not if our MMs have it though, but some cars do.

[Blackened300a]

IMO there is an internal leak in the Master cylinder.

I agree with you John, this is why I have a master cylinder sitting in the box that Im preparing to install soon. My pedal with enough pressure will hit the floor as well, I bled them and even put new fluid in with the same result.
Once I change the master Ill post results.

[bigbillybbs]

Possbl leak...

[burt ragio]

If this were the case that it is not normal for the brake pedal to continue to go down while under pressure while in park why would the service man say it is normal for our cars to do that when he could sell me a new master cylender ? Once again this only happens while in park.

[justbob]

You should in all cars experience a very slight difference in brake pressure when sitting in park and i mean very slight almost no difference. It sounds like you still have air trapped somewhere. When i bleed i always start farthest from master and work closer RR LR RF LL maybe even a quick second pass. Tell your dealer to put it in writing or you won't except. I bet they will look into it a little further first.

[Blackened300a]

If this were the case that it is not normal for the brake pedal to continue to go down while under pressure while in park why would the service man say it is normal for our cars to do that when he could sell me a new master cylender ? Once again this only happens while in park.

My fluid isnt leaking anywhere and I can stop fine. The way I know something is up with the master is because I never had this problem til recently and I have all new pads and rotors on the car, I also have a 99 crown vic and it doesnt have this problem. Plus other members will chime in that they dont have this issue as well so it has to be something wrong.

I have learned over the years of taking my car to dealerships is that the service manager for the most part dont know much about cars. I had a service manager tell me that the oil in my transfer case of my avalanche has to be changed every 1000 miles (Yes 1000 miles) I was told about these magical tools they have that can pinpoint squeaks and rattles. Most recent on my Marauder when I told them my starter was going, he insisted that its the shield of the convertor thats making the noise. The service manager will tell you anything to make you feel better. They are like a salesman for the service department. There are always exceptions but I have yet to find one for myself.
Your master must have a internal leak, I checked all my calipers and lines, the master will leak internally and cause a loss in pedal pressure. Are you sure its just park, I can do it in any gear as well, It just goes down easier in park.

[burt ragio]

When the brake system was bled they started out by hooking up the tool to bleed the ABS system. Then bled it all around twice. I was not near enough to see when they did the first bled. I could not see how much fluid they drained out. It was in sequence 1st right rear & 2nd left 3rd front right 4th left front. It sounds like what I'am hearing is I still have air in the ABS system or a internal leak in the master cylender ?

[justbob]

If this happened immediately after the install of the ss brake lines then it would leave me to believe it has something to do with that and not the booster. Do you have access to another mm to check the difference?

[Mike M]

Check the back of your master, chances are there is a wet stain dripping down your booster. You need to replace the master if your brake pedal sinks under pressure.

[BigCars4Ever]

The master cylinder is propably shot. Mine was. Prepare for some sticker shock. It's a Marauder only part only at the dealer. Don't waste your time with going anywhere else. All the other parts guys will have a MC that wll fit but the front/rear resevouirs are reversed which would require some major plumbing work. Mine set me back about $215.

[Marauderjack]

www.rockauto.com

[FordNut]

Sounds like air tapped somewhere. Possibly in the ABS pump area. When my brakes were upgraded they hooked up a machine that eliminated all the air. My pedal does not gradually go down to the floor.

[Spectragod]

The master cylinder has an internal leak, been there, done that, had to argue with the dealer who said it was normal on my Sport, replaced it, and all the planets are in line now. Oh yeah, my car is under warranty, which makes me think the response is what it was.