slight brake drag - left rear - 2004 Town Car Ultimate-L

[Jryan]

Gentlemen and Ladies - but probably mostly Gentlemen...

2004 Town Car Ultimate L experiencing a left rear rotor temperature that is 30°F-ish above that of the right rear rotor after driving. Front rotors remain at expected low temps. LR rotor temps highest at the rotor surface swept by the pads, lower at the hub indicating it's likely a slight drag of the service brake. Car also pulls a bit to the left. Having completed the following, I'm stumped and would appreciate any suggestions or input.

Please note that the condition started when I flushed the brake fluid and bled the brakes - to get fluid thru the ABS I activated the ABS and traction control with car on jackstands - it set an ABS code and trac code - both of which I reset via scantool

- caliper replaced with new Cardone unit (which included slide pins, boots and of course piston and square seals)
- caliper mount clips replaced (the thin stainless steel u-channels that clip onto the torque bracket on which the caliper slides
- rubber brake hose replaced

Condition persisted, therefore tried the following
- Activated the left rear ABS inlet and outlet valve via scan tool - closed, open several times
- Disconnect hard line at junction (frame rail below master cylinder) and at ABS valve body - flushed lines with brakleen and compressed air
- Prior to and after the flush, the disconnected caliper hose did drip fluid - seems to indicate free of blockage - maybe?

Condition persists

If bad master cylinder (comp port covered) wouldn't I have drag on two channels (two wheels?)
Any chance my ABS or HCU is clogged or has a stuck valve pintle?

Input / suggestions welcome - conspiracy theories OK too. If nothing else, hoping the above was mildly entertaining and I'll keep you posted

-ryan

 

[11MarkX]

1) I don't see that you replaced the rotor. Could be the rotor was always out of spec., and maybe the caliper had air, so became hotter after bleeding/caliper was now operating at 100%.

2) The rods/valves inside the ABS might not be seating properly. I didn't know you can activate the ABS on jack stands. Instead I found a snowy or gravel road and stomped on the pedal to activate those rods in the ABS at least twice. Then I bled system again. You might have to do this twice as I had to do. (My abs light was on, ABS not working, low brake pedal, even after mutiple bleedings. Everyone seems to spend hundreds replacing the ABS and master cylinder, when sometimes its just old dirty brake fluid that needs to get flushed. I flushed all the brake fluid out in 2021....High pedal since and ABS still works.

 

[Jryan]

Hi 11MarkX - thanks for the response - good thoughts. You are correct in that I have not yet replaced the rotor - looked in good shape but it's a inexpensive swap and worth a try.

The air-in-caliper is a decent thought as well. The pedal was firmer after the flush / bleed. Indeed as an experiment I injected via a syringe a known slug of air into the bleeder to see if the problem would go away. Initial results seem to indicate this made a difference in rotor temp, without adding undue sponginess to pedal. This is less a solution than an investigative step...

And just to relay my experience - the ABS / trac control seemed to activate when on the jack stand - calipers pulsing, set the ABS and trac control light - it was quite a show. I wouldn't recommend it - maybe learn from my mistake on that one...

I'll be a bit limited in further testing for now - they salted everything up here north of the mason-dixon and she's tucked in for the winter...