87 TC ABS & Barke warning lights on

Hi all,

I posted a newbie intro in the New User forum but I guess it hasn't been modded in yet.  

Anyway I just picked up a nice fully loaded '87 TC with manual trans for a great price, of course with several bugs to work out.   One of them was that the ebrake wouldn't work (kinda important for an MT, ha).   Diagnosed that as crusty cables and calipers.  So I rebuilt the rear brakes with new calipers, rotors, pads, and cables, and of course bled the system in the rear (UGH but fluid coming out was nasty!).  

The ebrake finally works again, and the brakes are OK, BUT now the ABS and Brake warning lights stay on.   Could this be caused if I still have a tad too much drag in the ebrake cables when released?   They were proving a real PITA to dial in and adjust so maybe I don't have it quite right.   Sadly, my working space is on an incline which makes things... tricky.    

My other potential culrprit is the new calipers had the "tang" or stop or whatever you call it by where the brake line attaches, a little too big, so as a result the bolts wouldn't go in.   Rather than file the tangs (which I feared would get shavings and debris right into the caliper line), I filed the shoulder of the brake line fitting.  So now they fit!  But even with using the copper crush washers on each side, I'm wondering if there isn't a slow leak under pressure?   I could see maybe that causing a light if the ABS system has to pressurize things.  But unfortunately I didn't get time to fully test and troubleshoot this before I had to leave on a stormchasing vacation,  but I'm hoping ya'll might have some ideas I can investigate when I get back late next week?

Thanks all for your time.   I already put some tips and ideas here to good use!

-Tony L.

Too much brake drag will not turn on either the BRAKE or ABS lights.

Yellow ABS light on is likely due to damaged / disconnected wheel speed sensor, incorrect gap between ABS sensor(s) and the tone rings.

There is a tech article I wrote year ago about checking / testing the ABS system for codes that should lead you in the right direction.

Thanks Jeff! In the time since I submitted the post and it was finally approved/posted here, I had to dig in further and did find your article.

What seems to be the situation now is I may have a failing PWS, oh joy. UNLESS it's possible I still have some air in the system and the PWS can be sensitive to that?

Anyway, the brakes work just fine now, but after some random / indeterminate time, both brake service lights come on, the pedal goes firm with no power assist, and the pump motor doesn't run. Following your guide I narrowed this to the PWS connector/component (the motor runs when PWS connector pins 1&4 are jumped).

As a workaround, I rigged up a "manual override" using a momentary SPST toggle switch. So when this happens, I can run the motor to charge the system; release the toggle when the lights go out and all remains well for a surprising amount of cycles. Well more than the 20 allegedly common for a good accumulator. So I don't know what's actually causing this condition, but needless to say it seems I'll be hunting for a PWS very soon.


BTW, it seems these PWS problems are endemic on many if not all cars that used the Teves II system. The Buick Reatta forum has some very good writeups, including a cross list of several other GM cars that used it. It seems those may use slightly different 5pin connector, but nonetheless our Tbirds (and Lincolns, et al) are listed in Buick forums as a source of parts, go figure.

Can you hear the pump running (part of master cylinder)... if it keeps running perhaps a leak or stuck relay??? If the pump doesn't run check the relay Under the black cover by the vacuum tee on the firewall. I know the red brake light will illuminate if the fluid is low (among other reasons). Generally an antilock light on by itself will still allow the brakes to function (just no antilock), when both lights are on, be careful as you may get the "hard pedal" where the brakes are just about useless.

So first check is the pump motor which you hear when you first turn the key.

Hi Vegas_ss, thanks for the tips. Seems my posts/responses are still on "must be approved" status. But yes, I've honed in on what you said. I think at the moment the pressure switch is not completely failed, but flaky. Sometimes it runs, but not always. Meanwhile I have rigged a momentary toggle switch to run it when the warning lights come on. Whether I get 200 or 1000 brake applications between events (who can count really, but it's a LOT) is anyone's guess.

And yes, that hard pedal is sure not fun. A real eye-opening throwback to the pre-power-brakes-era I'm sure.