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intermittent ABS warning light + slow brake pedal return SOLVED

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2019 was a very challenging year, in many ways. One of the most exasperating issues I had to deal with was the brakes on the QuadCab. A random ABS warning light was first noticed while borrowing this truck for a few weeks in 2015, but once I started driving the truck regularly in late 2018, the ABS light became more frequent and longer lasting. The truck passed the annual safety inspection in February as the ABS light did not come on during road testing, but by late March, the ABS light became a daily occurrence. It was about this time that a heavy trailer was pulled that required setting the trailer brake controller, and while pulling this trailer through stop-n-go traffic, a delayed release in trailer brakes was felt in the truck and observed on the controller. In April, the original master cylinder began leaking internally, and its defective replacement started an almost weekly trip to local parts stores, dealing with even more defective remanufactured parts.

Remanufactured Parts Installed:
Master Cylinders: 2
HydroBoost Units: 8
Steering Gearboxes: 4
Front Caliper (L): 2
Front Caliper (R): 3
Rear Caliper (L): 5
Rear Caliper (R): 8

Replacement Remanufactured Component Defects Observed
  • Master Cylinder: Original unit began leaking internally at 200k. AA replacement unit had a spongy pedal that could not be corrected after 20 bleeding attempts over 4 weeks and was replaced under warranty.
  • HydroBoost: Original unit began leaking PS fluid into cab at 170k; OR replacement worked up to about 200k. OR units 2-6 would fail pressure test after bleeding, causing brake pedal to not spring back after being released. AA replacement delivered was wrong application; followup delivered replacement had Schrader valve installed to psi canister and was returned. AZ unit lasted for 4 months with gradually degrading performance until ultimately failing by not releasing brakes after hard braking, hissing loudly under dash, then releasing brakes. Pedal return travel would take 3-10 seconds; ABS warning light would illuminate. NAPA replacement worked immediately, and in sub-freezing weather.
  • Steering Gearboxes: Original unit began having choppy operation around 204k. AA replacement had a mounting lug that stripped on final torque. Replacement unit delivered had damaged input shaft and was returned. Followup replacement unit delivered had damaged output shaft seal and was returned. Second followup replacement unit delivered had slightly damaged output shaft that was corrected with careful filing.
  • Front Calipers: Original RF caliper not retracting fully, LF dragging at 206k. AA replacement units had loose bushings; NAPA LF replacement worked; RF replacement leaked at bleeder screw and was replaced under warranty.
  • Rear Calipers: Original calipers dragging at 206k. AA (2), OR (2) & AZ (4) replacement units had very loose bushings; AA RR casting cracked at bleeder screw; OR RR casting leaked at hose; NAPA RR replacement leaked at bleeder screw and was replaced under warranty.
Remanufactured Caliper Failure Summary
Remanufactured calipers varied in quality, with evidence of pitting and scarring on pistons. Advance Auto and O’Reilly calipers were packaged in the same box, with the only difference in labeling of Wearever and Brake Best. AutoZone calipers (with and without brackets) were packaged slightly different, but of similar quality. None of these castings had any coatings, so clean grey castings at the store quickly rusted in the humid TX air.

Bushings were visibly wobbly in their bores, suggesting that the castings had too much material removed during core cleanup. This could lead to the caliper not aligning properly on the bracket, causing a ratcheting action during brake release. Similarly, excessive boring could be causing pistons to wedge themselves in their bores during brake release. This was somewhat confirmed during caliper removal after road testing, when pistons were difficult to compress in their bores, then suddenly compressed smoothly. The cumulative effect was rear brakes that would not release after braking downhill in reverse without having to throttle-rock the truck. Also, an ABS warning light would illuminate when one of the sticking pistons would fully release at random times (sometimes while flying down the highway), causing a pressure spike at the ABS pressure sensor in the proportioning valve.

By contrast, NAPA bracketed calipers had much cleaner, blemish-free pistons, and the bushings moved smoothly in their bores with practically no play observed. Castings had been painted black, so they would not rust right away like the unpainted Advance Auto, O’Reilly and AutoZone units. Cost was about 10% more than the competitors’ defective units that were all returned under warranty. NAPA calipers were not perfect, however, as a RF and a RR caliper were found to be seeping at the bleeder screws. Replacement units ordered seemed to be working as required.

The irony here is that all units were found to be remanufactured by Cardone. The NAPA units had documentation from Cardone, whereas the associates at the other stores said that the units were rebuilt by Cardone and information on the internet seemed to confirm this.

I did not attempt to measure any IDs or ODs as I had no specifications to measure against and I was trying to make repairs quickly as this was the only vehicle I had available for 2019. With the exception of the 4 caliper castings that leaked, all calipers worked well during brake application but not during brake release. Since the brakes need to be cycled rapidly for the ABS to work, the poor brake release would register as a pressure fluctuation outside of accepted parameters and set a fault code in the ABS module, which would cause the random ABS warning light. This failure mode is not directly outlined in the factory shop manual, but several symptoms of poor brake release are outlined as failure modes of other components, such as the ABS wheel sensors, the HydroBoost assembly, brake hoses, even the power steering pump and hoses.

Root Cause Analysis
This truck was driven and maintained regularly for its first 150k miles, then effectively parked in a barn for 10 years, driven occasionally to perform short-trip chores...maybe 10k in those 10 years. Even though the brake system still functioned as needed, the gradual performance degradation went unnoticed as the truck was driven so infrequently and still passed annual safety inspections. But the random ABS warning light that started in 2015 became a daily occurrence as the truck began being driven daily in 2019. Each month, a new symptom would crop up, and consulting the FSM would yield a different repair for each symptom.

As more original components had been replaced, I noticed a paragraph in the FSM that covered quality of brake fluid in the ABS. Aging brake fluid begins to break down rubber components in the ABS, turning the brake fluid practically black as the rubber debris saturates the fluid. This causes brake hoses to weaken and seals to break down. The FSM recommends replacement of ALL components that have any rubber when the system becomes contaminated, which is everything in the brake system except the hard lines and ABS control module. Reviewing this truck’s service records, the brake fluid had not been flushed in over 10 years, so that old dark brake fluid finally caused the whole brake system to bite the dust.

Total brake overhaul time probably should take less than 40 hours, but chasing phantom symptoms and dealing with defective parts caused me to spend 155 hours overhauling the system. Countless hours of research were spent trying to solve this random ABS warning light problem by studying the FSM and doing research online, as well as all of the time spent dealing with defect returns.

Back on Track
After months of second-guessing and setbacks, gallons of brake fluid and power steering fluid (bought 32 ounces at a time), 3 ruined tires, 3 mildly flat-spotted tires, and way too much time spent reading about similar (but not the same) problems on internet forums, I finally got the brakes to function as they should, without leaks and with a firm and responsive brake pedal. This work was completed during almost 80° February weather, the day before a sub-freezing cold snap blew into the area. Test driving in the cold weather showed the brake pedal returned just as fast as it did in balmy weather. I could even tap the brake pedal rapidly to make the brake lights flash to alert following drivers, something I had not been able to do for years, which I had just chalked up to “oh it’s an old truck, it just doesn’t work that way I guess”. So the next day, I headed to the inspection station and the truck passed…a HUGE relief…

I learned that aging ABS components have to be kept in tip-top shape in order to work properly. Just because the brakes “work” doesn’t mean they are working as they should…hence the random ABS warning light. Flushing the brake fluid periodically is paramount; deferring this maintenance can be an expensive headache in the long run. But above all, knowing how systems work can help determine what problems need to be addressed, especially if defective replacement parts are thrown into the mix. This requires patience and perseverance, much the same as with a decades old buggy. As I told several of the auto parts store associates, I’m accustomed to ordering stuff and waiting a few days before I can do the repair…each different associate would look at me with some surprise at my statement, apparently patience is something they don’t see much these days in our everything-is-on-my-smart-phone society.

Another issue of note is brake caliper lubrication. Sil-Glyde is a silicone lubricant that is recommended for all brake components, including the rubber boots that encase the slide pin bushings. Permatex Disc Brake Lubricant specifically mentions that it is only to be used on metal-to-metal applications. Internet research found that several other disc brake lubricants that did not specify if they could be used on rubber components would actually cause rubber to swell, causing binding of the caliper on the slide pins. Oddly enough, Permatex and Raybestos training videos do not mention this issue, but Wagner does differentiate between metal-to-metal and metal-to-rubber lubricants. Following their instructions, the NAPA caliper bushings were lubricated, as well as the brackets for the spring clips, the contact points of the brake pads to the spring clips, and the brake pad back plates where they contacted the calipers. Most of these areas see very little movement, if any, but presumably the lubricant is to displace moisture to reduce metal oxidation at contact points, which degrades brake performance over time.

I do not think I could have tackled this complicated brake problem on a truck that is 6 years shy from being classified as a Classic by TX DMV if I had not run into similar hard-to-diagnose problems on much older machines. As with most multi-component systems, each component has a certain operating envelope it can function within for the system to be robust. When multiple components operate outside their respective envelopes, diagnosing the problem area can be difficult as the phantom symptoms produced confuse the issue.

The toughest issue to deal with was the defective remanufactured parts, as reman’d parts seemed to be the best available cost-effective means to deal with the declining brake performance. When buying these reman’d parts, the assumption is that they have been sold as meeting specifications required. Since these specifications are not available to the general public, trial-and-error was used to determine which parts were actually as advertised. And even then, it is assumed that this will be sufficient as the system is operating apparently as required, but not known entirely for sure if it is or not.

So I reckon if that barn find has been parked for 10 years or 50 years, ya need to check them brakes and plan on just changing everything out, maybe even the hard lines…otherwise, you’re gonna spend a TON of time chasing down problems piecemeal and spend a fortune doing it…ain’t nobody got time for that :cool:
 
After 10 days of no incidents, I had 2 consecutive days where the ABS warning light came on: once in stop'n'go traffic, the other while backing downgrade. The light would shut off after parking the truck for a few minutes then starting back up for another errand run. With all of my blahblahblah I forgot to mention something that I noticed that I had not read about anywhere. Whenever my ABS warning light would come on, there would be brake fluid on the inside of the rubber cap on the proportional valve. When I had my original sticking calipers, this rubber cap would have brake fluid seeping out from the cap, running down the prop.valve. When I replaced my originals with defective replacements, there was fluid all under the cap but no longer running down the valve. And with these better performing calipers, the cap stayed dry until the ABS light came on, but only left a dot of brake fluid on the cap. My guess was that the hydroboost drawing back on the master cylinder causes fluid flow to escape through the prop.valve relief port when the port cracks open due to the calipers retracting too slow. My belief is that these new functioning calipers need the new to wear off of them before they operate smoothly enough to not cause this pressure spike at the prop.valve. Stay tuned...
 
the intermittent ABS warning light can be reproduced consistently by backing downgrade too fast, especially on dry pavement...the light goes out after shutting the truck down and starting it back up...brake pedal still works like it should, brake fluid level is unchanged...when the light comes on, I can see a spot of brake fluid on the proportional valve rubber cap underside, which is a bit of an improvement because 2 weeks ago, that spot was a wet dot. My guess is that the rear calipers are wearing in so that they are less resistant to retracting than they were when new, but still a tad tight. This is all an improvement, just in time for the spring wet weather to make travel interesting and pucker inducing...
 
ABS warning light is now a random occurrence, but I am not driving much these days due to covid restrictions, so the brakes are not wearing in as fast as I would have liked. When I softly apply the brakes on unpaved surfaces after the truck has not been driven for hours, the ABS light comes on almost every time. But when I have driven the truck in town on paved roads, giving the brakes a good workout, the ABS light rarely engages. Brakes still are very responsive, and work very well pulling heavy trailers on pavement...pulling lighter trailers on unpaved roads trips the ABS light almost every time.

Several months ago, I began trying to wear the rear brakes in a little faster by jamming on the brakes when reversing. When done on paved surfaces, the ABS light rarely comes on afterwards for hours, sometimes days. Since I have started this abrupt braking while backing up, I have not seen one drop of brake fluid on the proportional valve rubber cap...this leads me to believe that I'm on the right track.
 
Most of late September and October was free of warning lights, so I thought I had turned a corner on this long journey of problem solving. In that time, I took 6 road trips in excess of 2 hrs each, having only taken 2 long trips the previous 8 months. Then we had a 3 day cold spell dipping into the 30s, the power steering pump groaned one afternoon, and the warning lights were back, on all the time. Occasionally, the steering wheel would grab at startup, and groaning became constant as the weather warmed back up. So I extracted the fluid from the power steering pump reservoir and it was dark, only able to see the amber fluid color at the perimeter of the clear plastic jar. I was stumped as to how dirty that fluid had gotten in less than 10k miles, since the entire power steering system had been replaced and flushed.

So I replaced the extracted fluid with nearly a pint of Lucas Oil ps fluid with conditioners, which is about half of the ps system capacity. I figured that fluid swap was worth a try, as it only took 15 minutes, compared to another flushing extravaganza, which takes upwards of 4 hrs (including cleanup). Within a week, I had about 200 miles on that fluid, and as advertised, the pump stopped groaning, and the warning lights became more infrequent and random, not having illuminated in the last 50 miles.

The proportional valve rubber cap is still dry, and no leaks on the brake lines or fittings, so it's looking more like the ABS problem has shifted from brake fluid contamination to power steering fluid contamination...whoduh thunk it :rolleyes:
 
Well, i changed my PS fluid this summer after a hose got a leak, so i had to drain the whole system and what i found on the bottom of the bucket afterwards guided me to install a real PS fluid Filter right away.
I can't understand why Ram didn't do this from factory and let all the debris go round and round and round...
 
Swapped PS pump fluid after about 3k when the groaning resurfaced and warning lights came back on. But I did notice a recurring scenario with our wild winter weather: when air temperatures were above 60°F and I set the parking brake fully, the ABS and park brake warning lights would come on almost every trip...colder weather, setting the park brake caused no problems. So I pulled the rear rotors, blew all of the crud off of the park brake hardware, jarred the brake shoes by hand to break any rust or gunk free, and readjusted the park brake. Now with the warming weather, the only time the warning lights come on are sometime after I set the parking brake. So after 30 yrs of driving manual transmissions and setting the parking brake out of necessity, I'm having to learn how to NOT set the brake with this automatic so I don't flat spot my new set of tires...cool :rolleyes:
 
This spring and summer have been unseasonably wet, so I've had to deal with a lot of slick conditions on paved and unpaved surfaces. This has led to a lot of ABS + BRAKE lights, for days at a time. As summer has begun to dry out a little, I've realized several conditions that occur to trigger these warning lights:
  • parking on sloped surfaces, with or without setting the park brake
  • driving on loose or slick unpaved surfaces
  • pulling a trailer without trailer brakes
whenever I've driven on a dry paved road in stop and go traffic after the warning lights have been on, the lights will shut off. I've swapped PS pump fluid when the groaning started again, which was after 5k, so that interval has lengthened a tad. This ongoing issue still makes me think that I need to be driving the truck more to wear in the remanufactured calipers as the stop and go traffic apparently unsticks whatever is sticking that is causing the pressure spike that is setting the warning lights, as no brake fluid has been seen on the proportioning valve rubber cap in months. But my schedule these days has me driving slow in rural areas then driving on the highway for less than an hour, so the brakes don't really get a workout like when I've driven in traffic. So I reckon I'll just keep managing the situation and force myself to drive into town for some DQ once a week so the truck brakes will work :cool:
 
Last week, I had the QuadCab tires serviced, and with the wheels pulled off, I took a look at the brake pads, and was disappointed to see the wear on the driver side front pads through the caliper windows. A few days ago, I pulled the calipers off to get the front rotors surfaced, and verified that the driver caliper pistons were the culprit as the inside pad was worn out after 25k while the outside pad was barely worn; the passenger front pads were virtually equally worn, and about half used up. I also found the driver hub assembly had purged a good bit of grease, and was quite a bit more difficult to rotate than the passenger hub assembly. At first I was very disappointed by this, but dug up my receipts and verified that the warranty for that hub expires at the end of this month, so I was able to get a new replacement hub assembly at no charge...dodged a $300 bullet there.

I went ahead and pulled the rear calipers off to clean and lubricate the friction mounting points on the pads and caliper housings with Sil-Glyde as I had done with the fronts. With everything put back together and pressure bled, the test drives while running errands were not as successful as what I had hoped, as the ABS light was back on intermittently instead of all of the time while ambient temperatures were in the 70s. When the temps dropped to the 50s-60s the next day, the ABS light was on intermittently albeit for much less duration. With the ABS light off, emergency braking worked well and did not trigger the ABS light, so that's nice.

I am hoping that the brake issues are winding down, with this last caliper sticking because it's a little tight and will wear in sooner than later. Winter and most of spring will be in the rearview mirror In 6 months, and I'll check the system out again. In the meantime, I'm keeping my fingers crossed that there will be no incidents with this ol' buggy. After installing 17 calipers, 8 hydroboost units, 2 master cylinders, 2 power steering pumps, and 2 steering gearboxes, I've had enough practice overhauling these brakes...spending all this time doing the same procedures over and over has been a real drag :rolleyes:
 
It has been a long three years of exasperation and discovery, but after 2 master cylinders, 10 hydroboost units, 4 power steering pumps, 2 steering gearboxes, 7 brake hoses, 17 brake calipers, 4 hub assemblies, 4 wheel speed sensors, a proportional valve, a salvaged hydraulic control unit, and a refurbished ABS control module, the QuadCab has taken several test drives in 70°F+ weather without any ABS warning lights. The brakes are not perfect yet, as the ABS light came on during a short drive, but that was coupled with a momentary herky-jerky movement in the steering wheel, which might be air in the hydraulics after hydroboost #10 was installed. This underscores the balancing act of the power steering and power brakes needing to be kept in good working order with quality components so that both aging systems can function properly.

As cooler weather had arrived, it became apparent that the power steering pump was groaning almost non-stop, so I opted to replace it under warranty. Pump #3 was short-lived, as it blew out on a trip back from Waco, leaving remaining power steering fluid with a burnt odor. Once pump #4 was installed and system flushed, hydroboost #8 began to fail, presumably from the burnt fluid degrading seals. Hydroboost #9 lasted about a week and began to have issues, and upon removal, it was clear that the input shaft seal had started leaking. Hydroboost #10 seems OK but the brake pedal does not snap back after being released, which it was able to do the first few test drives, with pedal return taking about a second to complete; #9 was taking almost 2 seconds to return after release.

I was still getting the ABS warning light, so eventually I found a mechanic that actually knew how to work on this truck, as the local dealership and 2 prominent repair facilities basically shrugged in ignorance of such obsolete technology. We spitballed ideas on how to deal with the odd readings he was getting on his scanner, especially while taking a half-hour test drive. I mentioned to him that both front hubs have been replaced twice, as dragging replacement calipers were heating up the hub sealed bearings to the point of cooking the grease that would purge out, making them difficult to rotate by hand, and that this high heat could possibly have fried the wheel sensors I replaced in 2018. This possibly explained some of the live data readings, but the storing and clearing of default codes by the ABS module was confounding as neither of us had seen this before. I surmised that the module had bad components that were leading to this erratic behavior, so I found a nearby outfit that could refurbish the module. With the refurbished module installed, no codes were stored on the first three test drives.

About 40 hours of work have been done on this ol' buggy in the last 4 weeks...that puts the tally to well over 200 hours work in the last 3 years, with less than 50 hrs being to replace components, and the remainder to replace defective components under warranty. That's a LOT of time spent doing the same tasks repeatedly, while other projects have been put on hold. I'm keeping my fingers crossed that I have done enough work to get this to pass inspection in February and to have a functional ABS for the remainder of my usage of this machine...had a close call with a UPS truck the other day, which underscores the lurking risk of getting T-boned by an uninsured motorist :rolleyes:
 
I thought I'd pass along a few observations about this extended repair ordeal. If any of the brake components are sticking, brake fluid will appear under the proportional valve rubber cap. Dragging front calipers will generate enough heat that the hub bearings will start puking out cooked grease, as well as fry the front wheel speed sensors. As these trucks age, it would be helpful every season to disconnect the ABS pump motor from the control module and energize the motor for a few seconds to keep the motor in good working order. And when replacing the power steering pump, following the FSM fill and bleed procedure will guarantee premature pump failure.

OK that last statement might be a little bold, but after replacing 4 pumps in 3 years, I figured out what the FSM should have said. Instead of turning the wheels to the right & left 20 times, I found out (by accident) to listen to the pump while turning the steering wheel (1 half turn per second). On the first turn, it will gurgle, but by the 3rd turn, a large sucking sound comes from that pump...sure enough, the reservoir was empty, so I filled it to the FULL COLD line and made 3 more right-left cycles, listening the entire time. More gurgling and less pronounced sucking noises are made, so fill the reservoir again. By this point, every other right-left cycle, I would observe the PS fluid for bubbles, and would wait for those bubbles to dissipate before continuing the cycling. I would repeat this right-left cycling, fluid observation, fluid filling procedure until I noticed that bubbles were too hard to see and fluid level had stabilized. This meant that around cycle 20, the pump was making hardly any noise, and by cycle 40, no bubbles were in the fluid. Then I would disconnect the rubber hose from the pump to the hydroboost hard return line, plug the rubber hose with a hex bolt, and add a clear vinyl line from the hard line to a clear plastic gallon milk jug I'd squeeze into the engine compartment, in the area where I had removed the intercooler to intake manifold tube. After pulling the fuse to keep the engine from starting, I cranked the engine for 5 seconds, turning the steering wheel +/- 90° several times while pressing the brake pedal. I would observe the fluid from the hydroboost for any foaming, and wait 5 minutes before repeating the engine cranking. By the 4th purge cycle, fluid foaming had ceased, and only a few ounces of fluid had been purged into the jug. At this point, I'd button up the system, fill the pump to FULL COLD, put some kitty litter on my concrete shop floor under the tires and lowered the truck. (kitty litter under the tires on a concrete floor lets the tires turn left and right without marking up the concrete, and is a little easier on the pump since the tires are pulverizing the kitty litter and not binding on the dry concrete) When I would start the truck and turn the steering wheel to the right and left again, the pump fluid was observed and flowing with no foaming, and very quiet.

When I replaced the power steering pump the first 2 times, following the FSM instructions, I would hear the the pump groan a bit, and within a few thousand miles, noticed that the fluid was getting darker and the pump was groaning a little more often to the point where I needed to replace again under warranty. The third pump let out a big groan on first startup, and lasted less than 100 miles before making a GD mess. I've only put just over 1k on this pump, but the fluid is still quite clean, and in sub-freezing temps, hasn't groaned a bit.

So what's so special about this alternative fill and bleed procedure? I realized that in between the lines of the FSM was the implication that air was being worked out of the system while fluid level was being maintained during the 20 right-left steering wheel cycles. If the right-left cycles continue with bubbles in the fluid, then the fluid will foam at startup, possibly puking out of the reservoir, and that's just a GD mess. If the fluid level is observed after each right-left cycle, then the fluid level can be maintained to avoid adding more air to the system, and if bubbles do appear, let them dissipate immediately before the next right-left cycle. Another benefit of this modified procedure is that I had very little fluid spills, so cleanup was quick. Following the FSM and cleaning up afterwards would take me 3-4 hours and I'd go through about a gallon of PS fluid, but doing the modified procedure took only 2 hours and 2 quarts of PS fluid (sorta implied in the FSM).

I hope this pump lasts and the brake parts work as they should, as this whole experience has taken a big chunk of my spare time and made me consider selling this old buggy that had been reliable for almost 2 decades before it went bananas. In the last few weeks, I am slowly becoming accustomed to not seeing those ABS + BRAKE lights on while running down the highway or around the countryside...but I still look o_O
 
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