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Another ABS Puzzle


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Greetings,

My mom and dad bought a new 1989 Reatta in August of that year. Mom drove it for 123,000 miles until 2005, and endured all the usual maintenance issues (headlight motors, window mechanisms, falling headliners, etc.) She also apparently had problems with the ABS system from time to time, but we were told that there was a bad computer module generating the CRT error messages and the inconsistent Red/Yellow dash light displays. In other words, the ABS was really working, but the lights were not (the ABS amber light is still on 90% of the time even though I've had successful anti-lock stops). The dealer said the computer was no long available.

Then in July 2005, Mom had the following experience:

· 95 degrees outside temp (she lives in San Antonio TX)

· Drove on freeway for about two miles (car had been parked in the sun for at least 2 hours.)

· Exited freeway and stopped for two lights.

· Released brakes and got CRT message (?low brake pressure?) and then when she re-applied the brakes, heard ?a sound like the groaning noise in the pipes of an old house when you barely turn on a faucet.? Some stiffness in the pedal.

· Parked the car in a nearby parking lot.

The car sat for 45 min until my dad got there and drove the car approx 6 miles home with no further messages, lights or pedal stiffness.

September 2005

· Same scenario

· Took the car to dealer ? the same service writer they had dealt with since they bought the car (they trusted him)

· Dealer pulled stored codes 27 and 21. Said they needed complete brake package, including the EBCM (which was now available??), all of which would cost $6385. (yikes!)

· They declined and sold the car to me (I?m a pretty good shade tree mechanic) at the end of March after Dad and I ran all the brake tests suggested on reatta.net. All 7 tests were within tolerance.

I drove the car without incident until the end of June this year. I was driving on the highway from Austin to Gruene in the early evening. Very hot outside temperature ? upper 90?s, the car had been sitting in the sun all morning and afternoon. Less than five minutes from my house I got stuck in start and stop traffic on the highway and had the same symptoms as before: the groaning noise when the pedal was first applied and ?Low Brake Pressure? alert on the CRT. During the groan the pedal was very stiff and the brakes hardly worked. After the pedal traveled about a centimeter (with much force on my part), the groaning would stop and the brakes would begin working almost normally. If I kept the pedal mostly depressed, the brakes would function well enough to deal with the traffic. If I let the pedal up all the way, the condition would reset, i.e. I would lose braking and get the groaning until the pedal traveled that first centimeter again. I?m theorizing that this is perhaps due to the front brake circuits kicking in after some resistance from the rear circuit is overcome. In any case, the one common factor in all three of these incidents is the hot outdoor temperature and the fact that car itself had been sitting directly in the sun for much of the afternoon prior to being driven. After the car cooled down in Gruene for a few hours, the brakes worked fine all the way home. It almost seems that the ambient temperature outside has something to do with the brake failure??

It?s also worth noting the brake system leaks fluid periodically. The leak is not consistent. Recently, I have pretty much determined that the leak only occurs when manually depressurizing the accumulator, e.g. as is done when topping off the reservoir. The leak is difficult to pinpoint, but it appears to come from behind or below the pump/accumulator assembly, perhaps where the pump integrates with that assembly. The system has gone for up to two months without leaking any fluid even after the last LOW BRAKE PRESSURE incident. I wonder if the seemingly rare low pressure condition (groaning and loss of braking power) is related to the leak condition.

Any theories? I?d be grateful for any insight into this matter. My hope is to narrow the problem down to specific part or seal rather than resort to buying a whole new ABS assembly.

Thanks for taking the time to read this rather long post.

Bill Doughty

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While none of the Teves ABS parts are temperature sensetive that I know of, something is wrong. You have a couple of choices.

(1) you could start replacing components, accumulator, pressure switch, relay, and maybe the pump. If you replace everything before finding the problem the total cost just for parts will be $700 plus, buying them at the lowest possible cost.

(2) you could get a rebuilt, tested and warrantied unit from Prior and the total cost is less than $700.

I live outside Georgetown and have some used accumulators and a pressure gage if you want to experiment.

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Code 21 is the main valve and would be consistant with a pedal that pushed back at you. With a loss of boost the pedal would depress a certain distance then get very hard. A main valve not fully closing will push back at you.

27 is Rear Outlet Valve. Both are in the TEVES body.

Might want to pull the codes again and see if the same (if you pull all codes and drive a bit the codes reset).

The EBCM (ABS computer in the trunk) very rarely goes bad so most people with "experienced" parts have them.

Given the range of problems all in and around the master cylinder, I suspect the best answer is a rebuilt unit from Prior.

If the main valve sticks open, you will not have any stopping power except pumping the e-pedal and downshifting. DO NOT DRIVE.

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Hi Barney.

Really, my second Reatta, before I did my first brake fluid flush did the very same thing to me in Louisville when it got stuck in traffic during a heat wave. This might be the same problem.

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Also, turn that dealer into your consumer affairs division that dela swith auto repiars. What a rip off. Over 6 grand? I'd get a detailed quote and then run it by consumer affairs. It's dealers like that which make it hard for anyone to trust repair shops.

Given they are Buick dealer, call the regional reps and ask them of over 6 grand is reasonable and what kind of Buick dealer is taking advantage of it's customers?

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I'd replace the fluid in the resevoir since it gets pumped around in the system and then bleed the lines.

What I've done is put a pan under that area of the car and carefully remove the rubber line behind the ABS pump at the bottom of the resevoir. There's a metal clip holding it. I've found it best to twist it to free it up and then pull it off. Drain until it's empty. Replace the line and fill it back up with fresh DOT 3, following the sticker on how to properly check the fluid level (pump brake pedal until it gets hard or 20 pumps, then check). Fire it up and be sure the system's up to pressure and the brakes are working, then hit the streets. Repeat after running some errands, then repeat. Repeat this a couple times. Then dump the fluid once more, refill, and bleed the lines.

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What would a "fluttering" relay do? I'm sure we've all seen this, where a relay would rapidly close and open due to impending failure (brrrrrup). Or the same condition with the pressure sensor? Combined with a bad accumulator, I can envision a rapid intermittent voltage to the pump making strange noise and function. As Barney suggested, I'd start with the easy and cheap (relatively) things and work my way up. And first thing, disable the anti-lock to eliminate that as a source.

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Same problem here Bill- the hotter the ambient temp, the greater chance my brakes will fail (particularily when excessive braking is required in start/stop traffic). I am pretty sure it is my main valve as I have replaced my pressure switch, accumulator & relays. Also, my tap & thump (last step on the brake test) are not what they used to be.

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Thanks, everyone. Sounds like a fluid flush couldn't hurt things. Anyone know the boiling point of brake fluid offhand? I'm curious about that theory.

I'll check the stored codes again and see what indicators there are there. Thanks for your offer, Barney. I may take you up on that. I'm not ready to bite the $700 bullet just yet.

Around the time I bought the car, I started entertaining the idea of refitting the brake system with a non-ABS master-cylinder that would feed the existing wheel circuits. The idea is that I could get a traditional master cylinder for a fraction of the cost of a rebuilt Teves unit. I wonder if anyone has ever done this. Perhaps the Riviera non-ABS master cylinder from the same year would be a place to start. Ideally, I would find a simple hydraulic master cylinder that fits the bolt pattern and actuator interface on the existing vacuum booster. Does this seem reasonable or am I being overly ambitious considering such a conversion? Anti-lock functionality is not really an important feature for me in this climate and maintenance on a simple hydraulic system would be cheaper over the long run.

Bill

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The Riviera did have a non-ABS brake system but it had a seperate line to each wheel while the TEVES has one line to the rear.

There were several GM X-bodies in the 1976-1980 period that did have three line conventional power brake systems. Maybe a Riviera brake booster and master cylinder and an X-body distribution system.

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Aloha Bill,

You might want to physically check the ABS wheel sensors on each wheel. Its the one with an electrical connector inside the fenderwell that runs down into the wheel spindle where the ABS magnetic teeth is mounted to give an electrical pulse to the ABS Control Module.

If the wires are frayed, its time to replace those sensors.

Might want to pull them out of the wheel spindle to check if the end surface is cracked. If it is, moisture from rainwater/road salts have destroyed the sensor. Good time to clean the end of the sensor also as it gets some sludge deposits. Sensor is removed with a torx head screwdriver or use the torx tip with a ratchet to remove the screw.

You can also pull the ABS pressure switch without draining the hydraulic fluid, but be sure to pump the brake pedal at least 16-20 times to depressurize the system. You can tell when it is depressurized as the brake pedal will bottom out and become very hard to press down.

Moisture in the hydraulic fluid usually corrodes the pressure switch so it would be obvious with visual rusty internals that its time to replace the pressure switch.

Did the above to my 88 Reatta and the yellow light is off and the ABS is working again.

If the yellow light is on, don't be concerned as the brake system is working but the ABS is not.

My 89 Reatta's yellow light is constantly on, but haven't had the time to pull the wheel sensors and/or replace the pressure switch.

Might want to clear the ECM error messages by following the Reatta service manual procedure after doing any repairs so you get the correct indication if there are any electrical problems.

The 88-89's CRT display is great as it shows the condition and voltage readings as well as visual error codes to see exactly what the sensor is reporting.

The ABS wheel sensor is not in the CRT screen diagnostic realm so a physical check is called for.

Be sure to periodically flush the brake system out so moisture doesn't build up in the system.

Moisture = Rust and Corrosion.

In topping off the brake fluid reservoir, be sure to depressurize the system, then fill the reservoir to the top-off line.

When the system is energized, the fluid will be below the top-off line, but that is normal.

Do not overfill the reservoir by topping off without depressurizing the system.

You might have experienced fluid leak from the reservoir cap if you topped-off the reservoir without depressurizing the system.

If you plan to keep the car, which I would recommend you do as the Reatta is a great sportscar, I would invest in a service manual to see the do's and don't's.

I would see the dealer only as a last resort....

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Might want to check the brake calipers for fluid leaks around the caliper pistons which would cause a low brake pressure indicator as fluid might be leaking past the O rings on the pistons.

ABS parts come up for sale on eBay periodically if you need BCM, a complete ABS brake system pump unit, etc. A few months ago, an eBay member offered to overhaul the unit for about $200-$300 which I though was reasonble.

By the way, if you have headlamp problems, I bought those nylon headlamp bushings as a cure to the brittle/soft factory bushings to cure those floppy headlamps.

Usually its those factory bushings that cause headlamp motor problems and not the motor itelf.

A very weak spot in the headlamp assembly is the aluminum lever from the motor shaft which connects the motor to the headlamp assembly. The electric motor's steel slotted shaft justs eats the aluminum lever up.

I soldered a slotted copper bushing with locking threaded 1/4" bolts to lock the lever in place on the shaft as a cure.

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As far as your brakes groaning and loss of braking power, I would check your brake calipers/hoses for any fluid leaks. Wet brake pads would make your brakes groan as the rotor is sliding in your wet brake pads.

As I recall from the Reatta Service Manual,if your ABS accumulator is bad, when depressurizing your system, it would take only about 10 pumps or less to hit a hard brake pedal.

Normal depressurization is 15-20 pedal pumps before a hard brake pedal is reached.

In Hawaii, 90F road surface is normal and your brakes should not be giving out.

I would pull the wheels off to check for leaking calipers, worn/wet brake pad lining, and hoses for wet spots which would indicate a leak.

Flush the brake system completely out and replace with new brake fluid.

Going back from the calipers, brake hoses and lines, it leads back to the ABS Teves pump assembly.

Accumulator replacement part cost as I recall was around $100 and the ABS wheel sensors were about $80 a pop.

Might want to check if the accumulator is included with a rebuilt or new pump or take a chance if you do have a bad accumulator to just replace the accumulator to see if it was the cause of the problem.

I would pull the ABS pressure valve switch out to see in what condition its in and whether it needs replacement. Cost of the switch the last time I checked was around $125.

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