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        General >> Problems >> 1988 ABS grief
        
(Message started by: Ike Aruti on Nov 25^th, 2005, 10:24pm)

Title: 1988 ABS grief
Post by Ike Aruti on Nov 25^th, 2005, 10:24pm

Hello all:

I don't know if the 1988 (USA) model is too old for you folks, but I have one with me in Mexico, and the brakes are giving me grief for the first time since it was new.

The abs and brake lights both come on for about one second when I apply the brakes. During this time, braking force is seriously reduced, but returns to normal feel after about a second. Almost as if there is air in the system and the accumulator must briefly re pressurize upon applying the brakes. I have bled them twice, some air did come from the rear calipers. The wheels lock up upon heavy braking. All wheel speed sensors measure approx 1100 ohms. (Teves MKII system)

Is there anywhere else to bleed in this system?
Any other thoughts or suggestions would be greatly appreciated.

Friendly regards,
Ike

Title: Re: 1988 ABS grief
Post by Eric_R on Nov 27^th, 2005, 2:20pm

Aruti,
This model is a little early for ours, but welcome.

By your description is sounds as though the vacuum reservoir isn't operating quite as it should.

With the earlier Teves ABS you can interrogate the system by finding the diagnostic port tucked away near the battery IIRC. A local garage can plug into this and by grounding one of the contacts it sets the abs light to flash a code - this will tell where the fault is located. Years ago I knew how to do this, but I can't remember the wire to ground and I can't find the instructions now in my archive. I'm sure your local garage will know how to do it.

Good luck.

Title: Re: 1988 ABS grief
Post by Ike Aruti on Nov 30^th, 2005, 3:58pm

Hi Eric_R:

Thanks for taking the time and effort to reply. I have checked for a diagnostic port by the battery (passenger side firewall) did not find anything. There is a vacuum reservoir there, but it seems only to be connected to the cruise control. It also seems to be the only vacuum reservoir on the car. The brakes do not have a vacuum booster, nor any visible vacuum lines.

While I do not have the service manual, I do have the electrical and vacuum troubleshooting manual. The electrical schematics for the ABS system do not show or mention a diagnostic connector. The vacuum schematics do not show a vacuum connection or reservoir. The book does make reference to section 12-29 of the shop manual, which I do not have.
Additionally, other information I have found relating to the Teves MKII (TevesMkIIABS.pdf at http://www.autodiagnos.com) says the system has no self diagnostic capability, and does not mention vacuum interconnection.

I have bled the system four times now. Each time some air came from the rear calipers, none from the fronts. The first time the brakes became worse, with the warning lights staying on longer, brake pedal hard until the lights went out. Each subsequent time produced less air, but improvement in braking and reduction of the time the warning lights remain lit. I have followed the rear bleeding procedure found elsewhere on the web: ignition on, brake pedal applied, open bleeder screws for 10 seconds. I have put almost a liter of fluid through the system. No more hard feel to the pedal, but warning lights still come on briefly each time the brakes are appled.

Flexible hydraulic lines show no signs of deterioration nor swelling when the brakes are applied. I am waiting for a wet day to check to see if ABS operation has returned.

Friendly regards,
Ike

Title: Re: 1988 ABS grief
Post by howiedintheplace on Nov 30^th, 2005, 8:35pm

Your system is the same as on a Sierra & Granada over here. The two light's indicate a major problem.

Is it real hot there as this sometimes happen's when the fluid gets too hot in the engine bay?
Also the red light will come on if the pressure drops, have you got a leak?
Diagnostic's? didn't know that, I thought it was all multimeter readings & a bit of head stratching on the Mk2 system? ;D

Title: Re: 1988 ABS grief
Post by Ike Aruti on Dec 1^st, 2005, 3:45pm

Hi Dave:

Thanks for the note. There is no visible fluid leak, though now all is somewhat stained up from all the bleeding sessions. Maybe one more bleeding before I go back to NY, if that doesn't do it perhaps more life insurance is the answer....

It does get quite hot here in summer, max. about 38C. Altitude is over 1500m and sun gets quite strong, and vehicle is black, so underhood summer temp must be extreme. I don't understand how that causes air to get in rear brake circuit...

Red & yellow lights still come on very briefly, and I haven't had the opportunity to check ABS functioning yet. If this should turn out to be an accumulator / solenoid problem, I will probably junk the car, as part costs and Mexican import duties will easily exceed value of the car.

Friendly regards,
Ike

Title: Re: 1988 ABS grief
Post by howiedintheplace on Dec 2^nd, 2005, 4:34am

No Ike the heat does not let air into the system?

It causes problems with how the system works, yours is the other way round to our cars as in brake fluid holder on the left yes? Not sure if that makes a difference but if the engine bay of a car over here gets too hot like traffic or if you fit turbos etc it causes both lights to come on & the brakes to fail. You have to wait for it all to cool down before they are O.K again. Both lights will flicker a few times when breaking just before this happens, just a thought really?
We have to fit heat shields to the ABS system to prevent it on turbo cars, the MK3 Granada Cosworth had these shields for this very reason but is not a problem at all on the Scorpio's as they are different.

If you get this problem after you have been stuck in traffic or on very hot days, it could be the cause.
Old fluid does not help either.

Title: Re: 1988 ABS grief
Post by Ike Aruti on Dec 2^nd, 2005, 12:11pm

Hi Dave:

The problem you describe happens on my 1985 V-8 Capri race car. After a session on the road course, I pull into the pits, and after 5 minutes my brake pedal is gone. Half an hour later it is back like nothing was ever wrong. I put an air duct from the fender well to the master cylinder and the problem went away. I think this was the fluid (or moisture therein) vaporizing from heat and later condensing when cool.

The problem with the Scorpio came about after summer and the high temps were finished here in Mexico. The problem did not go away by itself as it does in the race car. I will guess that all the brake fluid is new in the system now after so many bleeding sessions. I believe what I have is air, and it seems only to affect the rear circuit.

Friendly regards,
Ike

Title: Re: 1988 ABS grief
Post by howiedintheplace on Dec 2^nd, 2005, 7:22pm

I bet that Capri is a handful on the corners ;)
We can rule out the heat then.
Well if you think the problem is on the back you must have a leak somewhere ???
It sounds like a pressure drop, if the yellow light comes on ABS is not working & if both come on it means you should stop as your brakes may not work or the fluid is low & ABS fault:o
When the red light comes on you should hear the ABS pump kick in to build up pressure again.
Try it with the engine not running but the ignition on & with some one else pressing the brake so you can check it out for leaks under pressure.