Question about 2008 Mercury Mariner

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It just loses pressure all the time and can be quickly pumped back up. and there is gunk in the fluid - would just cleaning the booster and master cylinder, and putting it back with new brake fluid fix this problem?

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Are you meaning you have a hard brake ? it is hard to brake? if so ,it is because your brake is lack of vacuum pressure. then you need to change a new vacuum brake booster , you can visit us for more information at : http://ca1020012840.fm.alibaba.com/

Posted on Nov 17, 2013

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2006 toyota tundra sr5 crew cab 4x4 losing brake fluid in the booster ? What do I replace there seems to be some kinda control valve maybe for the abs in between the master cyclinder and the brake booster...


Take Off Nuts That Hold Master Cylinder To Booster. Pull Master Cylinder Away From Booster--Do Not Damage Lines--Feel With Finger At Rear Of Master Cylinder For Fluid--If Found Replace Master Cylinder And Booster With Total Unit Combo For Better Warranty. DO NOT FOOT BLEED--Pressure Bleed Or Gravity Bleed Only.

Feb 19, 2015 | Toyota Cars & Trucks

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2001 Dodge van 3500 losing brake fluid but can't tell where fluid is leaking


Visual Inspection Back Of Wheels and Along Lines Front And Rear--Check Back Of Master Cylinder (will have to be unbolted and moved slightly away from booster) If Found Wet- Master Cylinder Leaking From Rear--If Vacuum Booster--It Will Fail Soon
Buy As A Combo--Already Together--For Best Warranty. NOTE: DO NOT FOOT BLEED--Gravity or Pressure Bleed Only In Sequence RR-LR-RF-LF

Feb 18, 2015 | Dodge Cars & Trucks

1 Answer

07 raider, brakes go to floor, no fluid lose.


Your brake master cylinder needs to be replaced, it sounds like it has a bad seal in it. f it was a caliper you would have fluid loss, and if it was your booster you would not be able to pump them back up. It is just losing pressure slowly. Change your master and make sure to bench bleed the master first, I hope this helps

Dec 13, 2013 | Cars & Trucks

1 Answer

Vacum leak on vacum booster for brakes


check vacuum hose first and make sure it's seated properly and not leaking.
This vacuum hose, if leaking, will cause engine to run rough or die.

If you are leaking fluid, the problem is most likely the master cylinder leaking.

If the booster itself is bad, it is a very hard job to swap it out as the mounting bolts are far behind your gauges on the firewall.

I hope you have a good booster.

Jan 27, 2013 | 1987 Nissan Pickup

2 Answers

Brake pedal go all the way to the floor


Check for brake leaks. Make sure that the resevore is full. With the engine off pump the brakes then check for leaks. If there is no leaks then bleed the brakes start with the right rear and work clock wise around the truck. If there is no air that comes out of the lines and the fluid looks clean your master cylinder went bad and it is a easy replacement. To replace the master cylinder you'll need a 14 mm for the lines and a 15 mm for the booster. Thanks!

Mar 07, 2011 | 1997 GMC Sierra

8 Answers

Changed calipers rotrs pads still no brake presure wont pump up to bleed air out of lines could master cylinder or booster be bad


Booster is okay, you have to bench bleed the MC, first. So, since it is installed, bleed it with a kit from the parts store, little plastic hoses screw in to the brake hose fittings, and put other end under fluid in reservoir. pump slowly, especially wait at end of release, for fluid to refill piston chamber....pump until no bubbles...

FROM THIS POINT you must not allow fluid in reservoir to go low, or start all over again....

Now bleed the brakes and you will eventually get pressure.

Mar 01, 2011 | 1998 Dodge Neon

1 Answer

Brake peddle goes all the way to the floor. brake peddle will have pressure when the car is off, but when you turn it on brake peddle loses all pressure. how can i tell if its the master cylinder or the...


first make sure there are no brake fluid leaks, sometimes the steel lines get rotted and start leaking. to test the booster with the engine off pump brake pedal about 10 - 12 times on the last pump hold the brake pedal down and start the car if the booster is good the pedal will drop alittle.

Feb 02, 2011 | 1994 Oldsmobile Cutlass Ciera

2 Answers

When I start the truck, brake pedal goes down on it's own and will not come back up unless you pull it up , Booster?


The booster is working properly if the pedal goes down a little when starting the truck. Seems more like it's a master cylinder problem if it won't pump up.

REMOVAL & INSTALLATION Fig. 1: Disconnect the warning indicator at the master cylinder 88289p00.jpg
Fig. 2: Remove the fluid to minimize the amount that would otherwise inevitably be spilled 88289p01.jpg
Fig. 3: Unscrew the line fittings at the master cylinder 88289p02.jpg
Fig. 4: Hold a rag under the fittings to keep fluid from dripping all over things 88289p03.jpg
Fig. 5: Unbolt the master cylinder from the brake booster 88289p04.jpg
Fig. 6: Remove the master cylinder from the vehicle and set it in a clean location 88289p05.jpg
  1. Disconnect the negative battery cable.
  2. Apply the brake pedal several times to exhaust all the vacuum in the system.
  3. Detach and cap the brake lines from the master cylinder.
  4. If equipped, detach the brake warning indicator connector. NOTE: A turkey baster (tapered tube with a squeeze ball on top) works well for removing fluid from the reservoir (see photo).
  5. Siphon off the fluid from the master cylinder reservoir to minimize spillage when lines are disconnected.
  6. If applicable, disconnect and cap the Hydraulic Control Unit (HCU) supply hose at the master cylinder reservoir and secure in a position to prevent loss of fluid.
  7. Unfasten the 2 nuts and lockwashers that attach the master cylinder to the brake booster.
  8. Remove the master cylinder from the booster by sliding it forward and upward from the vehicle. To install:
  9. Install a new seal in the groove in the master cylinder mounting face.
  10. Position the master cylinder assembly over the booster pushrod and onto the 2 studs on the booster assembly.
  11. Install the retaining nuts, then tighten to 18–25 ft. lbs. (24–34 Nm).
  12. Uncap and connect the brake lines to the master cylinder. Tighten the front fitting to 16–21 ft. lbs. (21–29 Nm), and the rear fitting to 10–15 ft. lbs. (15–20 Nm).
  13. Uncap and connect the HCU hose to the master cylinder reservoir fitting and secure with a hose clamp.
  14. If equipped, connect the brake warning indicator.
  15. Fill the master cylinder with Heavy Duty Brake Fluid C6AZ-19542-AA or equivalent DOT 3 brake fluid from a clean, sealed container. Bleed the entire brake system, as outlined in this section.
  16. Connect the negative battery cable.
  17. Operate the brake several times, then check for external hydraulic leaks.
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Aug 03, 2010 | 1992 Ford F350

1 Answer

Install new brake pads and rotors all 4 wheels. Replaced front 2 calipers. Bled brakes. New clean fluid coming out. pedal is still soft and goes to floor. 200 Seebring.


Are you losing any Brake Fluid? Is it visible anywhere at the four wheels? Is it visible anywhere else?
The Master Cylinder may be defective. When you bled the Brakes did you maintain proper Brake Fluid Level in the Master Cylinder? If you didn't: and air entered into the Master Cylinder there maybe air within in the system in the Master Cylinder. You can bleed the Master Cylinder by removing the brake lines, adding more fluid, pumping the brakes, bleeding the air out of the system.
Are you losing Brake Fluid and can't find a noticeable leak? Then there is a good posibility that the rear seal in the Master Cylinder is leaking and the Fluid is going into the Brake Booster - which is the large wheel shaped drum located on the fire wall. In this case both the Brake Booster and the Master Cylinder will have to be removed and replaced. The Booster contains seals that Brake Fluid is very caustic to and will ruin these seals- causing future failures.
If no Brake Fluid is lost, no leak found: Check the Brake Booster Vacuum Advance. This should be connected to the outside of the Booster, attached to a hose, with the hose going to the engine. Check to see if this is working properly. Replace if needed.

Dec 31, 2009 | 2002 Chrysler Sebring

1 Answer

Experienceing loss of power to brakes


1. What is the Brake Fluid Level?
2. Are you losing any Brake fluid at all? Are there any puddles or noticeable wetness on the ground or on the tires/wheels? With vehicle parked, the reservoir filled (overfilled), and engine running: pump the brakes and check on the ground and back sides (inside portions) of the wheels. Look for any brake fluid leaks.
3. Leaks from Calipers usually means a leak from the caliper piston. The rubber seals will be wet.
Leaks from Drums usually means a leak from the wheel cylinder.
4. In any case of leaks from the wheels - replace the calliper OR wheel cylinder.
For caliper leaks: change the brake pads, and clean the rotors with brake cleaner.
For drum leaks: clean the drum and brake hardware with brake cleaner, and replace the shoes.
5. If no leak is detected from the wheel area's: check under the Master Cylinder for wetness indicating a possible leak.
6. If no leak can be found: you MAY have a rear seal leak in the Master Cylinder which is pumping Brake Fluid into the Brake Booster (that large disk looking thing attached to the fire wall, attached to the Master Cylinder in front).
a. Use a large drip/catch pan under the Van in the area on the Master Cylinder.
b. Disconnect the brake lines from the Master Cylinder using a flair wrench.
c. Remove the two nuts (12 or 13mm?) attaching the Master Cylinder to the Brake Booster. If you have been using a lot of fluid, and have found no leaks, here is a good possibilty that all that brake fluid has collected in the Booster; so when you detach the Master Cylinder from the Brake Booster, all that fluid will come rushing out!
7. If there is Brake Fluid inside the Brake Booster: there is no cleaning that out. Brake Fluid is very caustic to the seals inside the Booster and should be replaced.
8. Of course the Master Cylinder will also have to be replaced.
9. After replacing the Master Cylinder/Brake Booster - make sure you get all that spilled brake fluid off the engine compartment area parts! I use a brake cleaner, then mild soap and then water to rinse. Clean any Brake Fluid off Paint imediatley as it will quickly dissolves finishes and paint.
10. If no leak is detected and the Booster is clear, there may be problems with the Booster One-Way Valve. This is attached to the outside of the Booster and has a hose from an "advance" connected to it. This maybe malfunctioning where you are losing power. Replace this first before deciding to replace the whole booster (in cases of NON-LEAKS ONLY). If that did not work, there may be inner seals inside the Booster that have failed. That means a new Booster.
11. In any of the above cases: Make sure you bleed the Master Cylinder correctly and bleed the brakes (at each affected wheel) correctly. Any air in the brake lines will decrease your braking proficiency or could result in brake failure.

Let me know if this helped or if you have any additional information or questions. Feel free to contact me at FixYa.com!

Dec 10, 2009 | 1999 Dodge Caravan

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