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ABS tests - please assist


RobertWS
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I have a continuous yellow light and occasionally on startup, the red light takes unusually long to go out. like maybe a minute or two...

Test results of 5 test sets averaged:

1 - 9 to 10

2 - 16

fluid level about 1/2 inch above fill line

3 - 23

4 - 34

5 - 21/2 to 3

6 - about 1/4 inch below fill line

7 - no detectable pushback or audible thump

any guidance would be appreciated.

Thanks

Robert

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Averages of previous systems tested: (30+)

Test 1. 10

Test 2. 28

Test 3. 32

Test 4. 45-50

Test 5. 2 1/2 to 3

Test 6. 1/2 inch.

Test 7. Should feel tap and hear thump.

Your Test results :

1 - 9 to 10

2 - 16

fluid level about 1/2 inch above fill line

3 - 23

4 - 34

5 - 21/2 to 3

6 - about 1/4 inch below fill line

7 - no detectable pushback or audible thump

Comments:

1. Seems O.K.

2. Indicates some lack of volume of fluid under pressure (probably weak accumulator or internal leak).

3. 23. If Accumulator was good, offering resistance to pump, this time would increase. (a good Accumulator and an internal leak would probably increase this time above the good averages, 32+)

4. Same as # 3.

5. Puzzling! Suggest you depressurize the system (key off, pump pedal till very hard, pump a few more times). Remove the reservoir cap, use a clean syringe or folded , lint free cloth, something, and bring fluid level to precisely full, "on the line."

6. "About" won't work however after completing #5 above, then key on, wait for pump to stop-then do test # 5 again(push pedal to floor if it will go that far), record results, then recheck reservoir level w/ system pressurized. How much drop?

7. We'll see.

The results of # 5 and the amount of fluid drop (more than 1/2 inch) are sure indicators of bad Accumulator. If # 5. results remain within tolerances 2 1/2 to 3 we'll have to look elsewhere UNLESS reservoir level drop is more than 1/2 inch= bad Accumulator.

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Teves brake is made up of two different and mostly independant circuits: the boost system (red light) and the ABS system (yellow light). The ABS computer goes through a series of checks (POST) when initiated and one of the last is the Main Valve cycle (the thump). If the ABS is disconnected you will always have a yellow light and the self-test will never occur hence no thump.

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"I have a continuous yellow light...."

Not sure if Robert had yellow light go our during tests? He did enter a time for it's going out?

Thought we'd save the #7 results question until he determines the Accumulator's operation. Checking the relay and getting codes from ALDL.

Strange that more than several w/ problems/lights have different symtoms but a new Accumulator cures all!

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A constant yellow light is no reason for not driving the car. Red light is another matter/very dangerous! Also very dangerous if red light comes on intermittantly either when, or not, applying brakes!

Once reservior level resolved then retested to see the exact fluid drop from unpressurized to pressurized we can swap relays IF the Accumulator is good.

Goal is to resolve red light problem then resolve yellow light problem= (read codes at ALDL and test main relay).

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Removed some brakefluid to get it just at the line after test 2.

Reran the tests:

1 - ave 10

2 - ave 19

3 - ave 29.5 - yellow does not go out

4 - ave 44

5 - ave 2 1/2

6 - ave 16/32" or 1/2"

7 - no pushback or thump

Swapped relays and had no change in tests and yellow still stays on....

any thoughts?

Thanks again

Robert

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Instructions for retrieving codes from ALDL are in FSM and at reatta.net

Very simple and takes only about 5 minutes once you become familar w/ counting flashes.(note how to determine History codes and how to remove history codes.) You will most likely find the cause of constant yellow light.

1st.I would disconnect the electrical connections, clean, at the Main Valve and Pressure Sensor before retrieving codes (maybe a waste of time). Then see if yellow light goes off.

Cause of "sometimes Red light stays on for prolonged period?." Is it possible your brake light switch or Emergency brake release sometimes doesn't completely return to off? Next time red light stays on exercise Emer Brake handle and pull up on brake pedal to see if either extinguishes light. Resetting switch also easy.

Your brake test results seem within range except for #7. Not hearing or feeling the thump indicates the system is not being checked electrically to see if all is within tolerances and then activate Anti-lock(extinguish yellow light). The thump is the Main Valve being activated/cycled.

Padgett, any thoughts?

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Yes, the ABS is thoroughly Ex. See my previous post in this thread. Red light boost, yellow light ABS. You can have boost without ABS but not ABS without boost (if red light is on, yellow will be also unless bulb is bad).

May be disconnected (check computer in trunk) or missing.

If do get working, drive very carefully for a while because a sticking main valve can mean zero brakes (be ready to pump parking brake and downshift to 1st) even with good boost (thump at startup is main valve cycling).

With yellow on and red off, it will drive normally, just without ABS.

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Computer in the trunk is there and connected.....

Tried jumpering the brake fluid level switch - no effect....

I looked at all of the fuse descriptions and could find none marked ABS,

Are there fuses somewhere other than the fuse blocks?

The delay in the red light going out has not reoccured lately.

The only problem is a continuous yellow light.

I'm confused about reading the ALDL codes. In one place it says to jumper pin "B" to ground to get the ALDL codes. In another place it says to jumper pin "H" to ground to get the ALDL codes. It appears like jumpering pin "H" to ground will give ALDL codes for ABS diagnostics....Is this what I should do?

Thanks again for all the time and effort to get me straightened out

Robert

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  • 4 weeks later...

I diagnosed the problem to the point where it appeared that an ABS control module failure could be the only other conclusion. With the help of a replacement from Jim Finn, the yellow light problem has been fixed.

Thanks for all of the help from the discussion group.

Robert

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i have had my yellow light come on and i think my brakes are more responsive and safer if you ask me. i noticed it while i was driving so i pulled into a parking lot, my car tires lock with the yellow light on and increases my stopping distance by like 20 feet.

how can i remove abs (always have yellow light on) without making my brakes dangerous?

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I think most will agree:

An emergency stop w/ anti-lock is much safer and requires less distance than w/o anti-lock!

Have you given the car the brake tests at reatta.net ?

If your yellow light stays on, your anti-lock is disabled! or so the FSM states. I once had a steady yellow light however anti-lock was working.

Ir , after giving the car the tests and no solution presented, retrieve the ABS codes at the ALDL, instructions at site-pictures/charts/diagrams.

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i did my own test i got up to about 30mph in a large empty parking lot and stopped once i past a certain object. then i turned the car off then on and the light went out and did it again with the abs on and i stopped at a further distance. perhaps my abs isnt as efficient as it should be, when i push the pedal with abs it seems much softer then with out abs, also when i go over repeated small bumps my abs cause my brakes to kinda go out and i dont stop, i would much rather lock my tires up and waste some tread then ram someone on a bumpy road.

i also have slotted rotors and carbon fiber brake pads if that makes any difference, just a note

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Think you need to become a little more familar w/ the Teves!

Read some at site below.

Reatta brakes are spongy but if the pedal does not touch floor........usually O.K.

Not sure what you mean by soft? May have air in lines!

The Valve Block relieves pressure when a wheel is locking (anti-lock), cycles many times and action can be felt in pedal (chatter/feedback) and heard.

If you truly engage anti-lock, you will know it. Sometimes, usually, you have to really get on the pedal hard, like in an emergency.

Reporting here the results of the brake tests may get you the needed help to solve your problem!

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The "thump" (test #7) is what the ABS feels like when activated, just often quite a few.

I was getting an occasional "yellow" that would go away almost immediately and when coming to a brisk (not panic) stop would feel a few thumps. The code said right front sensor so I removed it (one torx bolt - think was a T-30) and cleaned both the seating area, the sensor and the splines on the axle. Put back and the symptoms have gone away.

Have heard of a few people feeling quite a few thimps on a normal stop which means there is a problem.

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