My brake pedal is going to the floor?

Tiny
JACKIE LYNN MATTINGLY
  • MEMBER
  • 2005 DODGE CARAVAN
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 225,310 MILES
Replaced master cylinder about 3 months ago. Brakes have been okay. Then about a month and a half ago one of the caliper bolts on driver side came out, replaced temporarily with makeshift then the other bolt (or guide pin) came out and both were replaced properly. About 3 weeks ago pedal started acting funny. It would alternate between working fine to requiring pumping in half pumps or it would go to the floor. Did my research (extensively) as I have with everything else and determined it to be the brake power booster so had it ordered and a couple days ago my husband replaced it. Now even after multiple and I mean multiple rounds of bleeding in the correct order we have no brakes at all. I have done even more research and the only thing that comes back is possibly the vacuum line from the master to the booster. Am waiting at the auto parts store for the brake like switch as the clamp has broken on it and my brake lights are stuck on. I really need to figure this out as I can't drive with only an emergency brake. If it is the vacuum how do we fix it? If not what else could it be at this point. I am lost. Thanks in advance for any assistance.
Do you
have the same problem?
Yes
No
Monday, September 7th, 2020 AT 3:36 PM

33 Replies

Tiny
JACKIE LYNN MATTINGLY
  • MEMBER
A bit of history in case it helps. In the past 6 months these parts have been replaced: Passenger side: sway bar link x2, wheel hub, and shock/strut assembly.
Was this
answer
helpful?
Yes
No
Monday, September 7th, 2020 AT 3:57 PM
Tiny
ASEMASTER6371
  • EXPERT
Good evening,

First, the booster will not cause a fading or no brake pedal at all. That is all hydraulic.

This has all the sounds of a bad master cylinder again. When you change the master cylinder, did you flush the system of all brake fluid?

https://youtu.be/WDxvEQrMkBg

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

I posted below the procedure for bleeding if you have ABS. It is required to use a scan tool to bleed the ABS unit itself or you will not get a pedal.

Roy

Standard procedure - Antilock brake system bleeding

The base brake's hydraulic system must be bled anytime air enters the hydraulic system. The ABS though, particularly the ICU (HCU), should only need to be bled when the HCU is replaced or removed from the vehicle. The ABS must always be bled anytime it is suspected that the HCU has ingested air. Under most circumstances that require the bleeding of the brakes hydraulic system, only the base brake hydraulic system needs to be bled.

When bleeding the ABS system, the following bleeding sequence must be followed to insure complete and adequate bleeding.
1. Make sure all hydraulic fluid lines are installed and properly torqued.
2. Connect the scan tool to the Data Link Connector. The connector is located under the lower steering column cover to the left of the steering column.
3. Using the scan tool, check to make sure the CAB (MK20e) or ABM (Mk25e) does not have any fault codes stored. If it does, clear them using the scan tool.

Warning: when bleeding the brake system wear safety glasses. A clear bleed tube must be attached to the bleeder screws and submerged in a clear container filled part way with clean brake fluid. Direct the flow of brake fluid away from yourself and the painted surfaces of the vehicle. Brake fluid at high pressure may come out of the bleeder screws when opened.

4. Bleed the base brake system using the standard pressure or manual bleeding procedure.
5. Using the scan tool, select anti-lock brakes, followed by miscellaneous, then bleed brakes. follow the instructions displayed. when the scan tool displays test completed, disconnect the scan tool and proceed.
6. bleed the base brake system a second time. check brake fluid level in the reservoir periodically to prevent emptying, causing air to enter the hydraulic system.
7. fill the master cylinder reservoir to the full level.
8. test drive the vehicle to be sure the brakes are operating correctly and that the brake pedal does not feel spongy.
Was this
answer
helpful?
Yes
No
+1
Monday, September 7th, 2020 AT 4:21 PM
Tiny
CARADIODOC
  • EXPERT
This is not a power booster or vacuum problem. That entire system simply makes the brake pedal easier to push. If the vacuum supply is missing or the booster isn't working, the brake pedal will be hard to push and feel the same as when you push it multiple times with the engine not running. The brake systems on all cars are designed to operate sufficiently to bring the vehicle to a safe stop if the engine stalls. To test the booster, right after running the engine, turn it off, then apply the brake pedal multiple times. You should get a minimum of two power-assisted pedal applications, (three or four is not uncommon), then the pedal will become much harder to push. One exception to this is when you have anti-lock brakes, and that system also supplies the power assist. For example, my 1993 Dynasty has the Bendix-10 system that uses an accumulator to store brake fluid at up to 2200 psi. With that system, you get unlimited power assisted stops as long as the ignition switch is on, even if the engine has stalled, and around 40 pedal applications once the ignition switch is turned off.

When you have a low brake pedal, there has to be air in the system or a fluid leak. The fluid leak can be internal or external. An internal leak is due to a ripped lip seal inside the master cylinder. When you press the brake pedal, fluid bypasses that seal instead of being pushed under pressure down to the wheels. The clue is you will not be losing brake fluid from the reservoir. The level will go down if there is an external leak. Those are found by looking for the wet area, and following it back to the source. Slow leaks are commonly caused by leaking rear wheel cylinders if you have rear drum brakes. Rusted steel lines leak faster and will leave a puddle on the ground right under the leak. The fastest leaks are caused by ruptured rubber flex hoses. Those almost always go from no leak to a low brake pedal instantly with no warning.

Remember too that since the late 1960's, all vehicles have their brake systems split hydraulically into two parts, so even if a major leak occurs suddenly, you will still have half the brakes, but the brake pedal will be lower than normal, and the red "Brake" warning light will be on.

If your van has anti-lock brakes and air got into the system, it will usually be necessary to use a scanner to bleed that air out. If you try to bleed at the wheels, you'll force the air to travel through the system and it will get trapped in the ABS hydraulic controller. The scanners have a procedure that commands the ABS Computer to open two valves to let the air be expelled from two chambers, then it can be bled out at two of the wheels.

Bleeding at the wheels is not necessary when replacing the master cylinder as long as the new one is properly bench-bled before it is installed. When you replaced it, was that a rebuilt unit from an auto parts store, or a used one from a salvage yard?

There is one more thing that can cause a low brake pedal if you have rear drum brakes. That is brake shoes that are badly out of adjustment. The first clue is the low pedal comes on gradually, as in over a period of many months. The second, and bigger clue is you'll get a higher and harder brake pedal if you pump it one or two times first before holding steady pressure on it. With each pump the shoes get pushed out closer to the drums, but return spring tension retracts them so slowly that they are still part-way out when you press the brake pedal again. Each time you press the brake pedal, the shoes get closer to the drums, until they make contact, then pedal pressure will feel normal. When you release the pedal and wait a good four or five seconds, the shoes will have time to fully retract, then on the next application, the brake pedal will be low and mushy again.

Also take a look at this article related to a low brake pedal:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Don't overlook the work that was done on the front caliper mount. If the guide pins are not holding the caliper square to the rotor, excessive piston travel to get the pads to contact the rotor can result in excessive brake pedal travel. This is a variable we can only talk about in general terms until we actually see what is happening. Watch how much movement is taking place when a helper presses the brake pedal. When the brakes are applied, those caliper pistons only come out, then retract, a few thousandths of an inch. Not much more than the thickness of a few sheets of paper.
Was this
answer
helpful?
Yes
No
+2
Monday, September 7th, 2020 AT 4:54 PM
Tiny
JACKIE LYNN MATTINGLY
  • MEMBER
It was a rebuilt from the parts store. From what you explained in thinking that it could just be bleeding to be fled properly with the scan tool. Going to see if parts store has a loaner or how much on will cost. Thanks so much for the info will update as soon as I find out.
Was this
answer
helpful?
Yes
No
Monday, September 7th, 2020 AT 5:34 PM
Tiny
JACKIE LYNN MATTINGLY
  • MEMBER
Okay, so got the switch and he replaced it. Now no brake lights at all and with switch plugged in won't shit out of park. Take plug out and it will shift just fine but still no brake lights. Weird thing is that before he put new one in with the old one in and out we had brake lights and it shifted out of park just fine. By the way; haven't been able to get a scan tool that has the abs bleed capability yet so, standby.
Was this
answer
helpful?
Yes
No
Monday, September 7th, 2020 AT 7:45 PM
Tiny
ASEMASTER6371
  • EXPERT
Why did they change the brake light switch?

They should have never touched that as it had no bearing on the issue you have.

Worse case scenario is to call a mobile mechanic to come to you with his scan tool and bleed the brakes for you.

Roy
Was this
answer
helpful?
Yes
No
Tuesday, September 8th, 2020 AT 3:34 AM
Tiny
CHRIS2319
  • MEMBER
  • 2005 DODGE CARAVAN
  • 3.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 236,000 MILES
Brakes failed at a three way stop. They went to the floor with no stop. I bled the system roadside and it were good for three stops and then they went out again. Got the vehicle home. Looking in to what it may be. I removed the master cylinder. And it does not seem to have any problems.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:07 AM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good afternoon.

It sounds like the master cylinder has failed. It may be leaking internally and not allowing pressure to hold a brake pedal to stop the vehicle.

Roy

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
ANGELA RICHARDS- JOHNSON
  • MEMBER
  • 2005 DODGE CARAVAN
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
Hi, our van has been to multiple mechanics. We had good brakes but our ABS was not working. Our mechanic put in a new ABS module now the ABS is working, but the brakes are horrible unless I pump them. We have changed the calipers, master brake cylinder twice because we thought the first one might be faulty. All rotors and pads have been replaced, bled out the system by three different mechanics and the brake lines have all been tested for leaks by a certified mechanic and no leaks. We do not know what to do now, any suggestions?

Thanks,
Angela
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
AL514
  • EXPERT
The ABS module has to be bleed using a scan tool that can command the solenoids open. There is still air in the system, pumping up the pedal is just building pressure temporarily. Common issue when the ABS mod. Is replaced. They need to be bled correctly.
Was this
answer
helpful?
Yes
No
+1
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
ANGELA RICHARDS- JOHNSON
  • MEMBER
The dealership said that they did that, they bled the ABS system and said they activated the ABS module and that it must be the master brake cylinder causing the problem. After replacing it again we had the same result.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
AL514
  • EXPERT
Then they diagnosed the problem wrong. After replacing the master you will have to re-bleed the ABS system again or you will still have air in the lines. They should have been able to repair this problem for you from the start. They are the most qualified techs for this vehicle. There should be no reason they are not directing you in the right direction. They are supposed to be the expert's.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
BIGDBRODAA
  • MEMBER
  • 2005 DODGE CARAVAN
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
Today I was changing my brakes and realize that both my calipers where seized. So I bought the calipers changed them and after that I bled both side and straight fluid was coming out so there is no air in the lines. But when I turned on the van and drove it I had no brakes. I was pumping the brakes while driving to stop, so I bled them again. Both back and front this time to make sure there is no air at all, but nothing happened and still had no brakes. I checked all fluids everything is full. I don't know what is causing the problem but right now I have brakes only after I have hit the brakes all the way down to the floor.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good morning,

This sounds like you may have lost the master cylinder.

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

When you were bleeding the brakes, the master cylinder was going to the floor for the process. If the fluid is old and has not been changed regularly, dirt and debris in the cylinder can damage the seals and it will not hold pressure anymore.

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

Roy

REMOVAL - LHD

CAUTION: Vacuum in the power brake booster must be pumped down (removed) before removing master cylinder from power brake booster. This is necessary to prevent the power brake booster from sucking in any contamination as the master cylinder is removed. This can be done simply by pumping the brake pedal, with the vehicle's engine not running, until a firm feeling brake pedal is achieved.

1. With engine not running, pump brake pedal until a firm pedal is achieved (4-5 strokes).
2. Disconnect negative battery terminal.
3. Disconnect positive battery terminal.
4. Remove battery shield.
5. Remove nut and clamp securing battery to tray, remove battery.
6. Thoroughly clean all surfaces of the brake fluid reservoir and master cylinder. Use only solvent such as Mopar Brake Parts Cleaner or equivalent.

imageOpen In New TabZoom/Print

7. Remove wiring harness connector from brake fluid level switch in master cylinder brake fluid reservoir (Fig. 48).
8. Disconnect primary and secondary brake tubes from master cylinder housing (Fig. 48). Install sealing plugs in the now open brake tube outlet ports.

CAUTION: Before removing the master cylinder from the power brake vacuum booster, the master cylinder and vacuum booster must be thoroughly cleaned. This must be done to prevent dirt particles from falling into the power brake vacuum booster.

9. Clean area where master cylinder assembly attaches to power brake booster. Use only a solvent such as Mopar Brake Parts Cleaner or equivalent.

imageOpen In New TabZoom/Print

10. Remove two nuts attaching master cylinder to power brake booster (Fig. 49).
11. Slide master cylinder straight out of power brake booster.

CAUTION: A seal on the rear of the master cylinder is used to create the seal for holding vacuum in the power brake vacuum booster. The vacuum seal on the master cylinder MUST be replaced whenever the master cylinder is removed from the power brake vacuum booster.

12. Remove vacuum seal located on the mounting flange of the master cylinder. The vacuum seal is removed from master cylinder by carefully pulling it off the rear of master cylinder. Do not attempt to pry the seal off the master cylinder by inserting a sharp tool between seal and master cylinder casting.

INSTALLATION - LHD

CAUTION: Different types of master cylinders are used on this vehicle depending on brake options. If a new master cylinder is being installed, be sure it is the correct master cylinder for the type of brake system the vehicle is equipped with.

CAUTION: When replacing the master cylinder on a vehicle, a NEW vacuum seal MUST be installed on the master cylinder.

1. Install a NEW vacuum seal on master cylinder making sure seal fits squarely in groove of master cylinder casting.
2. Position master cylinder on studs of power brake booster, aligning booster push rod with master cylinder piston.
3. Install the two master cylinder mounting nuts (Fig. 49). Tighten both mounting nuts to a torque of 25 Nm (225 inch lbs.).

CAUTION: When tightening the primary and secondary brake tube nuts at master cylinder, be sure brake tubes do not contact any other components within the vehicle and that there is slack in the flexible sections of the tubes. This is required due to the movement between the ABS ICU and the master cylinder while the vehicle is in motion.

4. Connect primary and secondary brake tubes to master cylinder primary and secondary ports (Fig. 48). Brake tubes must be held securely when tightened to control orientation of flex section. Tighten tube nuts to a torque of 17 Nm (145 inch lbs.).
5. Install wiring harness connector to brake fluid level switch mounted in brake fluid reservoir (Fig. 48).
6. Install battery, clamp and nut.
7. Install battery shield.
8. Connect positive battery terminal.
9. Connect negative battery terminal.
10. Fill master cylinder with clean, fresh Mopar Brake Fluid or equivalent.
11. Road test vehicle to ensure proper operation of brakes.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
ZIONBLUE
  • MEMBER
  • 2003 DODGE CARAVAN
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 140,000 MILES
We have a Grand Caravan Sport (I think it's AWD) 3.8L Engine. I accidentally poured Power Steering into the break resovoir (Shoulda actually looked at the bottle before pouring) I tried to syphon as much out as I could when I realized what I was doing, But I am guessing it wasn't enough to prevent damage. I just topped off with Brake fluid and it was fine untill about a month ago.

- Pedal feels firm but loses firmness and sinks slowly to floor. Sometimes it stays firm and other times not

- Other times Pedal goes 1/2 to 3/4 of the way to floor and then gets firm.

- Sometimes it's strictly manual with pedal to the floor.

-Sometimes Pedal feels firm, sinks 1/2 way then brakes let go unless harder then they grip and unless I keep pushing they let go again.

- Pumping breaks does seem to help sometimes if done slowly as in tap let go, push let go, push let go But rarely.

- Fluid levels in resovoir remain full

- No Lights or indicators to show trouble

- Front Brakes changed in 2009
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
LEGITIMATE007
  • EXPERT
Yes the power steering fluid has finally caused damage the the propotioning valve. Hopefully you can come out of this by just bleeding the entire system dry and introducing new fluid into the system, prefferably synthetic. Or you may have to replace almost everything.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
R1S8P3
  • MEMBER
  • 2002 DODGE CARAVAN
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 125,000 MILES
Have problems with brake pedal going way down. Bled brakes and found air in left front only. (Lots of air.) Continued happening every couple days. Found what looked like a leak at master cylinder. Changed master cylinder. This did not help. Changed left front caliper and brake hose. There is no sign of leaking fluid, but I keep getting air in left front. Van does not lose any noticeable fluid in reservoir. Cannot get pedal to firm up solid. Will get better after bleeding, but always has a couple bubbles every time I crack bleeder. When I do bleed it I pump up the pedal and crack bleeder. It takes 4-5 times before I get hardly any fluid. A lot of air getting in somewhere.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
MHPAUTOS
  • EXPERT
HI there, often this is a faulty master, but as you have already changed it this is a bit strange, I would get 3 brake hose clamps and close off all hoses, see if the pedal is hard, re bleed with a power bleeder if yo can, keeping the clamps on the wheel lines that you are not bleeding, try this.

Mark (mhpautos)
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:08 AM (Merged)
Tiny
BC11860
  • MEMBER
  • 2004 DODGE CARAVAN
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 14,500 MILES
Hi, I put new pads & rotors on the front of my 2004 Grand Caravan ( front disc / rear drum ). Which I've done a few tmes before with no problems. Until now. I started at right front, took the caliper off, pads off and proceeded to push the piston back in with a c-clamp. After I did that successfully, I remembered that I didn't remove the master cylinder cap. Thinking there was no harm done, I finished the r/f brakes, proceeded to do the L/F but, decided to remove the M/C cap before pushing the piston in. Finished the L/F brakes no problem. Went to back out of the garage and the brakes would not "pump up"! OK, that never happened before, so I decided to bleed just the front, figuring the rears weren't affected and actuslly, I'm not quite sure how air would've gotten in the lines anyway. Aggravation sets in and I figured to bring it to a garage to let them look at it. The garage said it was a bad master cylinder. They installed a new cylinder, checked the rear brakes, bled all the brakes and said the pedal was good. Wonderful! I hop in the car start it and the pedal goes right to the floor! Wait, I shouldn't say that exactly because while I do have SOME braking, the pedal is spongy and when I keep my foot on it (say at a light) it will keep the braking but, the pedal will "weep" down to the floor? Bring it back to the garage and they say it has to be a bad M/C. OK, I'll buy that so, I leave it for 2 days and they call and say "we brought the car in the bay and the pedal pumped-up fine but, we noticed a "grabbing" on the R/R wheel, which we found was a blown wheel cylinder, which we replaced, bled the system, drove it around and it's working great. It wasn't a bad M/C afterall" OK, now they got it! Picked it up, after hours and wouldn't you know it. The same FREAKIN' problem is happening as when I first drove it in! I am totally baffled! I am getting braking but, the pedal is drifting rapidly to the floor! Is there any way it could be that the BRAND NEW master cylinder is still bad (entirely possible) or could it somehow be a bad brake booster? I'm at a loss and apparently so is the garage! I apologize that the donation isn't super high ( which I'm sorry for) but this brake problem is rapidly draining our finances. Which are slim to begin with.I sure would appreciate any help you could provide! Thank you.
Was this
answer
helpful?
Yes
No
Sunday, February 21st, 2021 AT 11:19 AM (Merged)
Tiny
MERLIN2021
  • EXPERT
Bleeding sequence here is LR,RF,RR,LF


https://www.2carpros.com/forum/automotive_pictures/62217_Caravan_Bleed_1.jpg


It sounds like a bad master, or not properly bench bled Of course with 145,000 if these are still original calipers, you may have pushed some sludge into the hieght sensing prop valve, or the abs system, is abs or red brake light on?
Was this
answer
helpful?
Yes
No
+1
Sunday, February 21st, 2021 AT 11:19 AM (Merged)

Please login or register to post a reply.

Sponsored links