1990 Brake Issue

[DAVES89]

I think you guys are way over thinking this. He has an intermittent ABS light. Get the car up on an jack stands, take off the wheels and inspect the sensor leads for cracks or breaks. Then put the wheels back on, unplug the leads and test the resistance with an ohm meter. You should get 800-1400 ohms. You can also give the wheels a spin and check the sensor to see if they read.

 A bad lead will give you weird counts on the ALDI.

 I am betting on a bad front sensor lead.

[Guest flajunkie]

2 hours ago, 89RedSlate said:

When was the last complete fluid flush performed?

 

Two weeks ago.

 

I appreciate all of the suggestions.

 

If you follow the failure of the ABS light to stay off, it follows a time period where the accumulator has apparently leaked down all by itself. After the accumulator is properly pumped up and some time period elapses, the ABS light goes off. It doesn't just come on in the middle of a ride like it would if an electrical component is failing.

 

The accumulator runs for a very long time after it has sat for over a day or two. That means something is bleeding off the pressure from the accumulator. There has to be a mechanical component that is allowing this.

 

I've asked before how pressure is maintained on the system when it is not operating and no one seems to know or has commented. There must be a valve allowing a slow leak in the system. That would account for the accumulator pump running for so long after a few days have elapsed.

 

Since the code focuses on a valve, I think this may be the area of the problem.

 

I will also try some of the other suggestions tomorrow.

 

Thanks again.

[Digger914]

A pump is not a one way valve and full pressure is not maintained in the system when the pump is off for an extended period of time.

 

The slow bleed down of pressure is absolutely normal. No different than a good old country private water well with pressure tank. So a water pressure tank has 60 to 80 lbs. turn the electricity off for a couple of days and as the stored pressure pushes water back through the pump impeller, pressure slowly drops to half, even if the pump packing is as good as it can be. Couple thousand pounds stored pressure in the brake accumulator and pressure eventually drops to half or less, but it doesn't go to zero and even after a few weeks you best pump down the pressure before you remove the accumulator.

 

The best way to screw up all ABS systems is to compress calipers and force dirty brake fluid backwards into the valve pack, so always open the bleeder when replacing pads and then bleed the brakes. A large empty lot is a good place to work the brakes, I use the open country freeway exit ramps. Works the system and cleans the glaze off the pads when your brakes get squeaky.

 

There is a factory gizmo that exercises the brake system and gives a real good bleed. Need to find a dealer that has one to get that done. There is another pressure gizmo that attaches to the reservoir that forces fluid through the system. Does a good job of pushing bubbles out of the valve pack, a fair job of pushing out crud, if it's not to thick and they are simple enough that they can be home built.

 

 

[Guest flajunkie]

10 hours ago, 89RedSlate said:

I'm wondering if intentionally making the system work- as in finding a large empty lot somewhere, get up to 35-45 mph, and stomping and holding the pedal down- cycling the valve block repeatedly- would free things up?

 

We can flush & bleed all day long- but it's not as if it's in a parts washer being cleaned out. Some residual gunk may still remain.

 

I think this is getting closer!

[Guest flajunkie]

On ‎9‎/‎21‎/‎2016 at 1:48 AM, Digger914 said:

There is a factory gizmo that exercises the brake system and gives a real good bleed. Need to find a dealer that has one to get that done.

 

What would I ask for?

[Digger914]

The Teves brake test set was a factory required tool purchase, find a dealership that's been around long enough that they would have been required to have one, then ask if they still have one and someone who knows how to use it. For this I think calling the smaller stores first, the ones that sold Buick, Pontiac, Olds and GMC all in one place. These little stores keep old tools forever and even if the last tech that knew how to use it has retired they tend to keep in touch. The bigger single line stores might still have the tool, but your car might be older than their brake tech so also ask if they have a Teves experienced tech in the shop.

[Guest flajunkie]

Update:

 

I took the car into the Buick dealer this week (they still have it) and told them to bleed the entire brake assembly again.

 

I check the next day and they are awaiting a code reader to see what's up in the ABS.

 

I tell them I know the code...and tell them what to check.

 

Instead, the tech says the pump is running too little and he thinks the accumulator never gets filled up.

 

He bypasses the relay and the accumulator fills up and the ABS light goes off. He has ordered two relays, will replace them and will bleed the brakes. i suspect the original accumulator was OK.

 

And i remember someone said something about the relays earlier.

 

I suspect some of you with intermittent ABS have similar weak relays.

 

I'll let you know what we finally figure out.

 

Oh and after all of this, she wants to sell the car! So someone is going to get a great deal on a beautiful Reatta convertible!

Edited February 10, 2017 by flajunkie (see edit history)

[padgett]

2 hours ago, flajunkie said:

 So someone is going to get a great deal on a beautiful Reatta convertible!

 

Don't tempt me. I suspect it is something simple. What bothers me is all the talk about the relay and pressure switch. If the pressure is low, the red BRAKE light should be on.

 

Given that there are a lot of diagnostic tests in section 5E1 of the FSM.

 

Finally EBCM trouble codes. I have learned that they are often rong or sympathetic (happen when something else is the problem). Cannot rely on what the manual says they are.

 

Are also some BCM codes (482 - low pressure) that may set. Also see BI18 and 21.

 

Isn't Indiatlantic on the other end of the Beeline (528) ?

ps

99	Electronic Controller (Clear memory Read codes … get 11 or 99 replace Electronic Controller)

[Guest flajunkie]

So two relays later, it works fine. I am guessing I now have an original accumulator for sale!

 

padgett, we are near the east end of the beeline (old timer, eh? That's what I call it, too!) south of Patrick AFB off A1A. You are certainly welcome to come look at the car!

 

As to the red brake light, it would come on as the pump filled up the accumulator. But I am speculating that it never ran long enough to kill the ABS light or fill up the accumulator for a longer duration between pumps. It works fine now...they didn't even need to bleed it again.

[waltmail]

I thought I had a relay problem for awhile. All I had to do to get the pump going was tap the relay. I replaced relay, since I had a box of spares. It would reoccur after awhile. So I would pop the relay. This would occur on  infrequent s tart ups. I pulled the relay again and this time sprayed the socket with WD 40. Never hung up again. It wasn't the relay just a dirty socket.            

[padgett]

Remember looking at a red one over there a number of years ago. Had quite a loud muffler.

[Barney Eaton]

While you seem to think the relay solved the problem, I suspect you have a bad pressure switch.

The pressure switch turn the relay on and off when the upper and lower pressure limits are reached. 

The relay itself never sees the pressure, it just takes input from the pressure switch.

I don't think "weak" is something normally used to describe a relay... bad contacts, stuck contacts, or a open coil will cause a relay to operate in ways not intended.

[ChrisWhewell]

8 hours ago, flajunkie said:

So two relays later, it works fine. I am guessing I now have an original accumulator for sale!

 

padgett, we are near the east end of the beeline (old timer, eh? That's what I call it, too!) south of Patrick AFB off A1A. You are certainly welcome to come look at the car!

 

As to the red brake light, it would come on as the pump filled up the accumulator. But I am speculating that it never ran long enough to kill the ABS light or fill up the accumulator for a longer duration between pumps. It works fine now...they didn't even need to bleed it again.

 

Save the old relay(s), bench test secondary circuit under load and look for drop in current, to verify.  Alternatively some funk in the primary circ.    That would acknowledge the issue was in the relay, and could be useful info.  Possibly as the contacts heat up, the point gap resistance increases

 

[Guest flajunkie]

22 hours ago, padgett said:

Remember looking at a red one over there a number of years ago. Had quite a loud muffler.

 

Wouldn't be this one. I have it on Craigslist right now.

[Ronnie]

My3Buicks? If so welcome back!