I have a motorhome built on a 1995 E350 chassis. when I got it, it had
about 20K miles. Now it has around 30K.
The brake pedal always felt soft and mushy. The brakes always worked OK, it
just didn’t feel like it should feel. And the ABS light was always on.
A few years ago, I took it to the garage to have the speedometer senser
replaced and it also needed the dimmer switch replaced. I asked about the
ABS light and they said there is a $700 hydraulic pump somewhere in the
system that isn’t working. It’s not supposed to be anything to worry about,
more annoying than dangerous. they said the brake system would work fine,
but the ABS light would always be on.
I’m wondering if the bad pump is the reason for the spongy pedal. The rear
brakes were just bled after a line was replaced and it’s solid fluid.
It stops great, it just doesn’t "feel" right.
Thanks
"Rick Sorber" <ri…@epix.net> wrote in message
news:O8jah.225873$PE1.187812@fe04.news.easynews.com…
- Hide quoted text — Show quoted text -
>I have a motorhome built on a 1995 E350 chassis. when I got it, it had
>about 20K miles. Now it has around 30K.
> The brake pedal always felt soft and mushy. The brakes always worked OK,
> it just didn’t feel like it should feel. And the ABS light was always on.
> A few years ago, I took it to the garage to have the speedometer senser
> replaced and it also needed the dimmer switch replaced. I asked about the
> ABS light and they said there is a $700 hydraulic pump somewhere in the
> system that isn’t working. It’s not supposed to be anything to worry
> about, more annoying than dangerous. they said the brake system would
> work fine, but the ABS light would always be on.
> I’m wondering if the bad pump is the reason for the spongy pedal. The
> rear brakes were just bled after a line was replaced and it’s solid fluid.
> It stops great, it just doesn’t "feel" right.
Did they reterive any trouble codes, or were they just guessing? Do you
know if you have rear wheel ABS or four wheel ABS? If they knew what they
were talking about, and you actually have an ABS pump, then you have four
wheel ABS. If you have four wheel ABS, you need a piece of test equipment to
retreive the trouble codes. To properly bleed the four wheel ABS system you
also need this piece of test equipment to instruct the ABS pump to initiate
a brake beeding procedure. If it is Rear Wheel ABS you can use the following
procedure to retreive the codes:
—-Begin procedure—-
On-Board Diagnostics
Diagnostic Trouble Codes, Retrieving
NOTE: Verify the key is in the RUN position (engine does not need to be
running). Next, locate the black RABS II diagnostic connector (RABS II
diagnostic connector located behind trim panel at far right side of
instrument panel, just below the instrument panel brace). The diagnostic
connector has two mating halves (one of which has a black/orange wire
connected to it). Disconnect the two halves.
Attach one end of a jumper wire to the black with orange stripe wire side of
the diagnostic connector. Momentarily ground the opposite end of the jumper
wire by connecting it to a good chassis ground for 1-2 seconds. Grounding
this wire should start the yellow REAR ABS warning light flashing. If
grounding this wire does not start the yellow REAR ABS warning light
flashing, go to the Symptom Chart .
CAUTION: Care must be taken to connect only the black/orange stripe wire to
ground. Connecting the mating connector wire to ground will result in a
blown fuse.
The code consists of a number of short flashes and ends with a long flash.
Count the short flashes and include the following long flash in the count to
obtain the code number. For example, three short flashes followed by one
long flash indicates diagnostic trouble Code 4. The code will continue to
repeat itself until the key is turned off. It is recommended that the code
be verified by reading it several times. This code will be used later for
system repair instructions. It should be written down for future use. A
diagnostic trouble code of 16 will be obtained when the anti-lock electronic
control module detects normal system operation.
Condition /
Possible Source /
Action
Red Brake Warning Light Inoperative or Does Not Self-Check
Open brake warning light bulb (red).
Open power fuse.
Open Circuit 640 (R/Y), 977 (P/W), 512 (T/LG), 531 (DG/Y), 162 (LG/R).
Open resistor/diode circuit.
Unseated master cylinder fluid level switch connector.
Defective ignition bulb prove-out switch.
GO to Pinpoint Test A .
Red Brake Warning Light Stays On When Key Is in RUN Position
Ground short on Circuit 977 (P/W).
Ground short on Circuit 162 (LG/R).
Damaged parking brake switch.
Damaged low vacuum switch (diesel only).
GO to Pinpoint Test B .
Yellow Rear ABS Warning Light Does Not Self-Check
Open fuse Circuit 640 (R/Y).
Missing power to rear ABS warning light (open Circuit 640 [ R/Y]).
Open Circuit 603 (DG).
Burned out yellow REAR ABS warning light.
Terminal backout in the anti-lock electronic control module harness
connector at Pin 7.
Harness connector not fully mated with anti-lock electronic control module.
Defective anti-lock electronic control module.
Open REAR ABS ground (Circuit 530 [LG/Y]).
GO to Pinpoint Test C .
Yellow Rear ABS Warning Light Self-Checks but Light Automatically Begins
Flashing
Intermittent anti-lock electronic control module.
Intermittent anti-lock electronic control module ground circuit.
Intermittent yellow rear ABS warning light circuit.
Blown Keep Alive Memory fuse.
GO to Pinpoint Test D .
Yellow Rear ABS Warning Light Self-Checks OK, but No Diagnostic Trouble Code
When Diagnostics Are Started
Burned-out brake taillights.
Missing anti-lock electronic control module power (Circuit 601 [ LB/PK] and
associated fuse).
Shorted yellow rear ABS warning light circuit (Circuit 603 [ DG]).
Incorrect anti-lock electronic control module type (RABS I vs. RABS II).
GO to Pinpoint Test E .
Yellow Rear ABS Warning Light Flashes Two Times When Retrieving Diagnostic
Trouble Codes (Code 2)
Terminal backout in the anti-lock electronic control module harness
connector at Pin 13.
Terminal backout in the RABS valve harness connector at Pin 1.
Bulkhead connector (between engine compartment and instrument panel)
terminal backout or loose connection.
Module or RABS valve connectors not fully mated with component.
Intermittent open circuit in Circuit 599 (PK/LG).
GO to Pinpoint Test F .
Yellow Rear ABS Warning Light Flashes Three Times When Retrieving Diagnostic
Trouble Codes (Code 3)
Terminal backout in the anti-lock electronic control module harness
connector at Pin 8 or 14.
Terminal backout in the RABS valve harness connector at Pin 4.
Bulkhead connector (between engine compartment and instrument panel)
terminal backout or loose connection.
Anti-lock electronic control module or RABS valve connectors not fully mated
with component.
Intermittent open circuit in Circuit 664 (Y/LG).
GO to Pinpoint Test G .
Yellow Rear ABS Warning Light Flashes Four Times When Retrieving Diagnostic
Trouble Codes (Code 4)
Terminal backout in the anti-lock electronic control module harness
connector at Pin 6.
Terminal backout in the RABS valve harness connector at Pins 2 or 3.
Bulkhead connector (between engine compartment and instrument panel)
terminal backout or loose connection.
Anti-lock electronic control module or RABS valve connectors not fully mated
with component.
Intermittent open or open circuit in Circuits 535 (LB/R), or 274 (BK/W).
Intermittent short or short circuit in Circuit 535 (LB/R).
Defective RABS valve.
GO to Pinpoint Test H .
Yellow Rear ABS Warning Light Flashes Five Times When Retrieving Diagnostic
Trouble Codes (Code 5)
Parking brake drag.
Rear brake assembly grabby or hanging up.
Connector corrosion or contamination.
Intermittent open circuit in Circuit 210 (LB).
GO to Pinpoint Test J .
Yellow Rear ABS Warning Light Flashes Six Times When Retrieving Diagnostic
Trouble Codes (Code 6)
Terminal backout in the anti-lock electronic control module harness
connector at Pins 3 and 10.
Terminal backout in the RABS sensor harness connector at Pins A and B.
Bulkhead connector (between engine compartment and instrument panel)
terminal backout or loose connection.
Anti-lock electronic control module or RABS sensor connectors not fully
mated with component.
Intermittent open/short circuit in Circuits 519 (LG/BK) or 523 (R/PK).
Damaged RABS sensor (possibly metal shavings on pole piece).
Damaged RABS sensor ring (possibly teeth missing).
GO to Pinpoint Test K .
Yellow Rear ABS Warning Light Flashes Seven Times When Retrieving Diagnostic
Trouble Codes (Code 7)
Anti-lock electronic control module fuse blown or internal open circuit.
Shorted isolation solenoid internal to the RABS valve.
Intermittent short or shorted circuit in Circuit 599 (PK/LG).
Contamination or bent Pins 1 and 3 of RABS valve connector shorting
together.
GO to Pinpoint Test L .
Yellow Rear ABS Warning Light Flashes Eight Times When Retrieving Diagnostic
Trouble Codes (Code
Anti-lock electronic control module internal fuse blown or internal open
circuit.
Shorted dump solenoid internal to the RABS valve.
Intermittent short or shorted circuit in Circuit 664 (Y/LG).
Bulkhead connector between engine compartment and instrument panel terminals
shorted.
GO to Pinpoint Test M .
Yellow Rear ABS Warning Light Flashes Nine Times When Retrieving Diagnostic
Trouble Codes (Code 9)
Terminal backout in the anti-lock electronic control module harness
connector at Pin 3 or Pin 10.
Terminal backout in the RABS sensor harness connector at Pins A or B.
Anti-lock electronic control module or RABS sensor connectors not fully
mated with component.
Open or intermittent open circuits in Circuit 519 (LG/BK) or 523 (R/PK).
GO to Pinpoint Test N .
Yellow Rear ABS Warning Light Flashes Ten Times When Retrieving Diagnostic
Trouble Codes (Code 10)
Short between anti-lock electronic control module harness connector Pin 3
and Pin 10.
Short between RABS sensor connector Pins A and B.
Bulkhead connector (between engine compartment and instrument panel) sensor
terminals shorted together.
Intermittent short circuit in Circuits 519 (LG/BK) or 523 (R/PK).
GO to Pinpoint Test P .
Yellow Rear ABS Warning Light Flashes 11 Times When Retrieving Diagnostic
Trouble Codes (Code 11)
Terminal backout in the anti-lock electronic control module harness
connector at Pin 11.
Missing (burned-out) stoplamps. All stoplamps must be missing or burned out
to cause a Code 11.
An intermittent/continuous open in Circuit 511 (LG). This open would be
between anti-lock electronic control module connector Pin 11 and the
stoplight switch.
Worn or damaged stoplight switch.
GO to Pinpoint Test Q .
Yellow Rear ABS Warning Light Flashes 12 Times When Retrieving Diagnostic
Trouble Codes
…
read more »
On Sun, 26 Nov 2006 16:19:59 GMT, "Rick Sorber" <ri…@epix.net>
wrote:
- Hide quoted text — Show quoted text -
>I have a motorhome built on a 1995 E350 chassis. when I got it, it had
>about 20K miles. Now it has around 30K.
>The brake pedal always felt soft and mushy. The brakes always worked OK, it
>just didn’t feel like it should feel. And the ABS light was always on.
>A few years ago, I took it to the garage to have the speedometer senser
>replaced and it also needed the dimmer switch replaced. I asked about the
>ABS light and they said there is a $700 hydraulic pump somewhere in the
>system that isn’t working. It’s not supposed to be anything to worry about,
>more annoying than dangerous. they said the brake system would work fine,
>but the ABS light would always be on.
>I’m wondering if the bad pump is the reason for the spongy pedal. The rear
>brakes were just bled after a line was replaced and it’s solid fluid.
>It stops great, it just doesn’t "feel" right.
>Thanks
It’s not a pump – its a variable accumulator. Under normal braking the
accumator pistons are all at "tdc" in their cyls. When lockup is
sensed, the piston in the accumulator for that system is driven down
and a check valve closed, reducing the pressure to that wheel until
the wheel unlocks. The piston modulates to hold the wheel just off
lockup. If the pedal is released, the fluid is allowed to return to
the MC.
If the accumulator piston is stuck in the lowered position it is very
difficult to totally bleed the system, as some air can be trapped in
the accumulator. This gives a low pedal.
You WILL have normal brakes with the ABS dissabled with one caveat.
MOST ABS brake systems are designed to be JUST capable of locking the
wheels under normal conditions, which often translates to lower brake
performance than a non-ABS equipped vehicle. I’ve experienced driving
both ABS and Non ABS equipped vehicles, otherwise the same, and being
able to lock all 4 wheels on the non ABS equipped vehicle with no
problem, yet not being able to force the ABS to engage on the ABS
equipped vehicle under identical conditions. Personally, I prefer non
ABS brakes, but when the ABS accumulator on my van failed, I fixed it.
When the brake warning light comes on I know there is a problem. If
it’s on all the time, the problem is not brought to my attention, and
it could become dangerous.
–
Posted via a free Usenet account from http://www.teranews.com
As Ed has indicated… it is important to find out whether your motorhome is
equipped with RABS or 4WABS…. the diagnostic process will differ between
the two.
From what I can see, your shop is shortchanging you on their assumption of
the system and what it may or may not have for concerns. And I haven’t even
mentioned that ABS is a safety system – ignoring it’s problems rate right up
with "no, we don’t need life jackets" and "ground strap? why?"…. but that
is just me….
If yours has RABS (and ALL other mechanical items in the brake system are
properly installed and functioning correctly)…. one possible cause would
be the RABS accumulator…. this is a smallish assembly on the frame rail
tied into the rear wheel brakes only…. IIRC, 4 or 5 wires on the plug (but
it has been a long time). At one end of the assembly is a hexagon cap…
this can be removed, the return spring taken out and the cap
reinstalled….. Pump the brakes several times through the spongy feeling
and remove the cap to see if the accumulator piston has moved outwards in
the bore…. If so, the valve is leaking…. Word to the wise – this is
brakes we are working with and care and caution need to be exercised
throughout the process.
If the van has 4WABS, the HCU/module assembly is in a difficult spot to
access if the shop can’t lift the van…. If they can’t lift it, they
shouldn’t be workiing on it…. but, again, that’s just me.
The truly sad part of any endeavour such as this is that a shop may or may
not have the abilities and/or equipment to repair some concerns. Rather
than risk losing a customer by saying we can’t do that, you’ll have to
elsewhere…. they would much rather attempt to keep you in their customer
base and blow the problem off….. after all, it’s just a stinking warning
light, right?
A GOOD shop would explain some of the possibilities, be able to give an
estimate of diagnostic time required and, after initial diagnosis, give a
detailed estimate of repair costs….
We aren’t talking about "fast food burgers" here… For many, their
automobile will be the biggest single "investment" they have or possibly
ever will make…. The opportunities for something to go terribly wrong with
one of these investments is staggering and, all too often (read the
newspaper), the cost is dear….
I can only suggest finding a shop more in tune with customer needs, that
will spend the time to discuss the repair of all of your vehicles with
you….