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Intermittent hard brake pedal


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joezapp
User

Jul 8, 2017, 1:28 PM

Post #1 of 42 (1248 views)
  post locked   Intermittent hard brake pedal  

Hi guys! This is an interesting one that I never experienced in 35 years of driving. Since Thursday I have experienced an intermittent hard brake pedal with my 1992 Town & Country. It has happened ONE TIME on each drive since. I'll step on the pedal and it will catch me by surprise by being hard and not wanting to push down. The van will slow some, but breaking ability is drastically impaired. After a few depresses, the pedal will finally function normally.

Does anyone have any idea what causes this? Also, I'll add that I had my pads and rotors changed 2 weeks ago, though it could be unrelated because the van was driven last weekend without issue, and the issue just arose Thursday (and continues).

Thank you for help with this!


Hammer Time
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Jul 8, 2017, 1:37 PM

Post #2 of 42 (1246 views)
  post locked   Re: Intermittent hard brake pedal  

Is it a "high" hard pedal or a "low" hard pedal when it does this?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Sidom
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Jul 8, 2017, 1:44 PM

Post #3 of 42 (1241 views)
  post locked   Re: Intermittent hard brake pedal  

It sounds like your brk booster may be going out....It's vacuum controlled and when it fails or you have a problem with the vacuum source it won't give any brk assist......

The usually complaint is ......" The pedal feels like it does when the car is off"


joezapp
User

Jul 8, 2017, 2:23 PM

Post #4 of 42 (1237 views)
  post locked   Re: Intermittent hard brake pedal  

Thanks for the quick reply, guys.

Definitely a high hard brake pedal, Hammer Time.

I see what you're getting at, Sidom. It makes sense. I have intermittent "no brake assist". So if the cause is an intermittent brake booster issue or an intermittent vacuum issue, how do I determine which it is?

Thank you!


Sidom
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Jul 8, 2017, 2:37 PM

Post #5 of 42 (1235 views)
  post locked   Re: Intermittent hard brake pedal  

You could check with a gauge but a quick check would be to pull the hose of the booster and feel the vacuum, plus it creates such a big leak that the engine will usually die, at the very least, run like cr@p...

Most of the time it's the booster going out.....Sometimes the master cyl will develop a leak in back and leak into the booster and cause it to fail....other times it just goes out.....it's just a rubber diaphragm in there


joezapp
User

Jul 8, 2017, 3:17 PM

Post #6 of 42 (1228 views)
  post locked   Re: Intermittent hard brake pedal  

Thank you, Sidom. A rubber diaphragm will likely go bad after 25 years. I'll do the check anyway to narrow it down. Thanks, again.


Hammer Time
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Jul 8, 2017, 3:17 PM

Post #7 of 42 (1228 views)
  post locked   Re: Intermittent hard brake pedal  

Yep, high, hard pedal is a booster issue. Like Sidom says, vacuum, valve or booster problem.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



joezapp
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Jul 8, 2017, 8:36 PM

Post #8 of 42 (1220 views)
  post locked   post icon Re: Intermittent hard brake pedal  

Thanks for narrowing it down for me, guys. It all makes sense now.


Double J
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Jul 8, 2017, 9:47 PM

Post #9 of 42 (1197 views)
  post locked   Re: Intermittent hard brake pedal  

If this has ABS , then it's going to have the dreaded faulty ABS Bendix 10 unit that Chrysler recalled
We all remember those.......

If so, look into Recall 685.....Parts are probably not available anymore.....

Summary:
THE ABS HYDRAULIC CONTROL UNIT CAN EXPERIENCE EXCESSIVE BRAKE ACTUATOR PISTON SEAL WEAR CAUSING PUMP-MOTOR DETERIORATION.
Consequence:
IF THIS CONDITION OCCURS, THE ABS FUNCTION COULD BE LOST AND REDUCED POWER ASSIST WOULD BE EXPERIENCED DURING VEHICLE BRAKING INCREASING THE POTENTIAL FOR A VEHICLE ACCIDENT. Remedy:
DEALERS WILL TEST THE VEHICLE'S ANTI-LOCK BRAKE SYSTEM AND REPAIR THE VEHICLES IF NECESSARY. ALSO THE WARRANTY ON ALL ABS COMPONENTS WILL BE EXTENDED TO 10 YEARS OR 100,000 MILES "EXCEPT FOR THE BRAKE ACTUATOR PISTON ASSEMBLY AND THE PUMP-MOTOR ASSEMBLY WHICH WILL HAVE A LIFETIME COVERAGE". OWNERS WILL ALSO BE REIMBURSED FOR PREVIOUS ABS COMPONENT REPAIR COSTS.


joezapp
User

Jul 9, 2017, 9:15 PM

Post #10 of 42 (1178 views)
  post locked   Re: Intermittent hard brake pedal  

This is good stuff, DoubleJ! I was completely unaware of this!! I had to replace the ABS Pump and Motor about 6 years ago. I had no idea about the recall or the lifetime warranty. Would that warranty apply only to the original owner?

I had to replace the ABS Pump and Motor because it was leaking. The symptom for that was the opposite of what the Consequence talks about. The pedal was going to the floor because off brake fluid loss. The symptom I'm having now is more similar to the Consequence mentioned. I would lean toward this being more of a vacuum/booster issue, but I must consider the Pump-Motor as well, especially since I got it used.

Thanks so much for this!


(This post was edited by joezapp on Jul 9, 2017, 9:27 PM)


Tom Greenleaf
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Jul 10, 2017, 3:13 AM

Post #11 of 42 (1169 views)
  post locked   Re: Intermittent hard brake pedal  

My 2 cents of what's likely with the symptoms are a breach of vacuum assist can be clogged hose, swollen or cracked hose from manifold vacuum to the check valve and rubber grommet it goes into or the booster itself.
At this age even 1/2 of that be ready with new hose, valve as it may bust just checking it AND the rubber grommet most are barbed may not seal again! Have on hand first if you possibly can.
If since pads/rotors just done pushed very old fluid thru brake parts there risk there as well to mess things up. Fluid show flow one way only towards calipers to retract piston(s) out bleeder not push backwards - no telling now how done.


Master cylinder's rubber seals DO NOT LIKE GOING TO FLOOR if older especially it's crusty deeper in and failure just from that common to me.


OMG if Chrysler used a rare set up and did as mentioned that becomes another problem now by age recall or not it may have expired and parts if that troublesome at best.


I'd just toss the vacuum hose (special hose required) , valve and grommet and then can test booster holds or doesn't and know those parts are ok for the fix or are the fix? Note if any brake fluid found at the check valve or dripping down back of master to booster connection too,


T

(edit some spelling errors out)



(This post was edited by Tom Greenleaf on Jul 10, 2017, 3:15 AM)


joezapp
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Jul 10, 2017, 2:24 PM

Post #12 of 42 (1147 views)
  post locked   Re: Intermittent hard brake pedal  

Thank you, Tom. Changing those parts on an old vehicle sounds like a good idea to do regardless, so I believe I will use the approach you suggest.

I never knew that fact about "going to the floor" and master cylinders. Good to know. Interestingly (and probably oddly), with all the old cars I have owned and in all my years of driving, I have never had a master cylinder go on me! I'd better knock wood right now!!


Double J
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Jul 10, 2017, 2:37 PM

Post #13 of 42 (1143 views)
  post locked   Re: Intermittent hard brake pedal  

Doesn't have a conventional vacuum booster assist on Bendix 10. Utilizes a hydraulic assist.


Found on 1991 Caravan/Voyager/Town and Country (AS body), the Bendix System 10 will prevent wheel locking under heavy braking. By preventing wheel lock-up, maximum braking effort is maintained while preventing loss of directional control. Additionally, some steering capability is maintained during the stop. The ABS system will operate regardless of road surface conditions.
There are conditions for which the ABS system provides no benefit. Hydroplaning is possible when the tires ride on a film of water, losing contact with the paved surface. This renders the vehicle totally uncontrollable until road contact is regained. Extreme steering maneuvers at high speed or cornering beyond the limits of tire adhesion can result in skidding which is independent of vehicle braking. For this reason, the system is named anti-lock rather than anti-skid.


Under normal braking conditions, the ABS system functions in the same manner as a standard brake system.




****The primary difference is that power assist is gained from hydraulic pressure rather than a conventional vacuum booster.**************






The system is a combination of electrical and hydraulic components, working together to control the flow of brake fluid to the wheels when necessary. The pump and motor assembly pressurizes brake fluid from the reservoir and stores it within an accumulator for use in both normal power-assisted and ABS braking. The Controller Anti-lock Brake (CAB) is the electronic brain of the system, receiving and interpreting speed signals from 4 sensors at the wheels. The CAB will enter anti-lock mode when it senses impending wheel lock at any wheel and immediately controls the line pressure(s) to the affected wheel(s). The hydraulic assembly serves as both an integral master cylinder and the hydraulic booster assembly for the brake system. It contains the wheel circuit valves used to control the brake fluid pressure to each wheel circuit.
During anti-lock braking, line pressures are controlled or modulated by the rapid cycling of electronic valves within the hydraulic assembly. These valves can allow pressures within the system to increase, remain constant or decrease depending on the needs of the moment as registered by the CAB. The front wheels are controlled individually while the rear wheels receive the same electrical signal, based on the wheel with the greatest locking tendency. Anti-lock function is available above 3–5 mph (4.5–8 km/h).
The operator may hear a popping or clicking sound as the pump and/or control valves cycle on and off during normal operation. The sounds are due to normal operation and are not indicative of a system problem; under most conditions, the sounds are only faintly audible. If ABS is engaged, the operator may notice some pulsation in the pedal. If additional force is applied to the pedal during an ABS-engaged stop, the operator will notice extremely hard pedal feel. This is due to isolation of the master cylinder during ABS operation. Some pulsing may also be felt in the body of the vehicle due to suspension movement as brake pressures apply and release at the individual wheels.
Although the ABS system prevents wheel lock–up under hard braking, as brake pressure increases, wheel slip is allowed to reach as high as 30%. This means that the rolling velocity of a given wheel is 30% less than that of a free–rolling wheel at a given speed. This slip will result in some tire chirp during ABS operation. The sound should not be interpreted as lock–up but rather as an indication of the system holding the wheel(s) just outside the point of lock–up. Additionally, since the ABS system turns off below 4 mph (7 km/h), the final few feet of an ABS–engaged stop may be completed with the wheels locked.
The Bendix system is equipped with built-in diagnostic capability. At every start-up, the CAB illuminates the dashboard warning lights and turns them off after checking the circuitry. When the vehicle reaches 3–5 mph (4.5–8 km/h), the CAB conducts a system check, briefly activating all the control valves to confirm their operation. This system check may be noticed by the operator as a series of rapid clicks during initial drive–off; the sound is normal and not indicative of a problem. Some fault conditions will cause the CAB to set and retain a trouble code which may be retrieved for diagnostic purposes. Stored fault codes will remain stored until cleared by the DRB II.
The CAB will illuminate the appropriate dashboard warning lamp according to the fault detected. It is possible to have a fault affecting only the ABS function; in this case, the ABS system will be disabled but the vehicle will retain normal braking capability.


Here is an excerpt about pedal feel with Bendix 10..........

The ABS system uses hydraulic power assist for both normal power assisted braking and to provide a source of high pressure hydraulic fluid during antilock braking.
In General, pedal feel will be similar to that of a conventional vacuum boosted brake system. If during an ABS stop additional force is applied to the brake pedal, or the brake pedal is released and reapplied rapidly, the driver may notice a very hard pedal feel. This is due to normal isolation of the master cylinder during ABS operation as wheel brake pressure is fed from the hydraulic booster.


(This post was edited by Double J on Jul 10, 2017, 2:39 PM)


Tom Greenleaf
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Jul 10, 2017, 2:49 PM

Post #14 of 42 (1139 views)
  post locked   Re: Intermittent hard brake pedal  

OK - There's enough here to check and keep you busy. I bring up the master on older can mean less than 10 years as people just don't usually make a routine of bleeding out all brakes for new fluid and not so sure it's on the list of things to do rather wait till it needs to from something else then you find it's not good even if not the problem fixed. It's plain embarrassing to do some stupid something and by surprise that needs doing and wasn't what you fixed from just having a low pedal that never went there for years.
Common brake fluid is dirt cheap really. The properties of say DOT 3 is to absorb moisture even from air leaving cap of container or off reservoir sucking humidity moisture into it and becomes less resistant to both heat and corrosion just a couple % of moisture wrecks it but works and gets ignored till something happens.


You call on doing thing proactively and how long you expect fewer problems for yet more time than this.


Hey - what could be safer than the best brakes possible of all features a car has?


T



Double J
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Jul 10, 2017, 2:57 PM

Post #15 of 42 (1135 views)
  post locked   Re: Intermittent hard brake pedal  

NOTE
WARNING!


If you work on this, learn the system first before opening any of the hydraulics.
The Hydraulic accumulator needs to be depressurized first. Its under very high PSI
Ignition OFF or battery disconnected, pump the brake pedal a minumum of 40 times


(This post was edited by Double J on Jul 10, 2017, 3:10 PM)


joezapp
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Jul 10, 2017, 3:44 PM

Post #16 of 42 (1123 views)
  post locked   Re: Intermittent hard brake pedal  

Thanks so much, DoubleJ. This is good stuff that you came up with for me. Many thanks!

That is a good point, Tom. I agree.

So Tom and Sidom, according to the research that DoubleJ provided to us...that my system is hydraulic assist rather than vacuum assist...this effectively eliminates the tests you both suggested for this particular vehicle (1992 Town & Country). Correct?


Sidom
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Jul 10, 2017, 5:00 PM

Post #17 of 42 (1117 views)
  post locked   Re: Intermittent hard brake pedal  

Yes, if your system isn't using a vacuum booster than follow the guidelines Jim provide for you...


joezapp
User

Jul 11, 2017, 10:16 PM

Post #18 of 42 (1106 views)
  post locked   Re: Intermittent hard brake pedal  

I will perform the checks for hydraulic brake assist and report back. Thanks for all the valuable input!


joezapp
User

Jul 14, 2017, 5:07 PM

Post #19 of 42 (1085 views)
  post locked   Re: Intermittent hard brake pedal  

I cannot emphasize enough how grateful I am for DoubleJ pointing out that I have the dreaded Bendix 10 ABS System that had a recall. It answered a lot of questions I myself had about this brake system over the past 9 years that I've owned it, be it noises, dash lights in the past, etc.

So now that I know I'm in a whole different ball of wax with hydraulic brake assist, how do I begin to diagnose my problem of "intermittent no brake assist"? Has anyone on here ever worked on these 1991-1993 Chrysler vehicles and troubleshooted this braking issue? I'd like to narrow down just where in this system the issue lies.

I'll remind, just in case it's a factor, that my pads and rotors were changed 2 weeks prior to this issue arising, but the van was driven for 2 days without issue in between.

Thank you!


(This post was edited by joezapp on Jul 14, 2017, 5:09 PM)


Hammer Time
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Jul 14, 2017, 5:18 PM

Post #20 of 42 (1081 views)
  post locked   Re: Intermittent hard brake pedal  

Are you have any issues with the power steering?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



joezapp
User

Jul 14, 2017, 5:22 PM

Post #21 of 42 (1077 views)
  post locked   Re: Intermittent hard brake pedal  

No, Hammer Time, not at all.

This vehicle has a dedicated hydraulic pump.


(This post was edited by joezapp on Jul 14, 2017, 5:29 PM)


Hammer Time
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Jul 14, 2017, 5:28 PM

Post #22 of 42 (1073 views)
  post locked   Re: Intermittent hard brake pedal  

It sounds like your issue is with that master cylinder and that is covered under lifetime recall. Why don't you bring it to the dealer?



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



joezapp
User

Jul 14, 2017, 5:41 PM

Post #23 of 42 (1069 views)
  post locked   Re: Intermittent hard brake pedal  

There are a bunch of ABS components. The master cylinder is separate from them. It seems owners have had mixed success going to the dealer. Part availability s an issue. Their knowledge of the system at this stage is an issue. And the total ABS (32 parts) was warrantied for 10 years/100,000 miles. After that, it's just 3 system parts...though they are big ones. (Hydraulic Assembly, Piston Assemply Actuator, and Pump/Motor Assembly).

If the dealer were to determine something other than those 3 parts, it'd be a large bill. So I'd be looking to diagnose where in the system my problem lies first. The fact that this is intermittent indicates that it may not be one of the 3 lifetime warrantied parts that is at issue currently.

Here is the latest warranty update:
http://www.autosafety.org/wp-content/uploads/import/Bendix%2010%20ABS%20System%201990-93%20Xler.pdf


(This post was edited by joezapp on Jul 14, 2017, 6:18 PM)


Double J
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Jul 14, 2017, 9:47 PM

Post #24 of 42 (1043 views)
  post locked   Re: Intermittent hard brake pedal  

I've worked on a few but only the normal things like replacing brake flex hoses, pipes ,pads/rotors, calipers,bleeding,etc.
All others I've shipped to the dealer for the warranty / recall


I do know the pump/motor assy takes low pressure brake fluid from the reservoir and pressurizes it for storage in the accumulators for power assist and ABS braking.
That being said, if a pump or accumulator were to fail it would affect " pedal effort "....
There are tests that can be done but proper gauges and equipment are needed.
You Can buy a Bendix 10 service manual and pressure gauges for these on Ebay.

I'm assuming you aren't getting any warning messages or lights


I've heard of people who have done the conversion to these and got rid of the Bendix 10 for a conventional system by using donor parts from a non ABS car of that year
BUT I don't recommend it nor would I go thru all that BS, time and money plus its not for the novice.


joezapp
User

Jul 14, 2017, 10:05 PM

Post #25 of 42 (1037 views)
  post locked   Re: Intermittent hard brake pedal  

 


(This post was edited by joezapp on Jul 14, 2017, 10:23 PM)






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