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I noticed I wasn't getting sufficient braking. So I decided to replace my brake fluid and bleed the system. Everything went well except when i was bleeding the fluid stopped flowing from the 'front right' and 'rear left' calipers.
Immediately checking the Master Cylinder it was still topped off and the pedal felt fine, even with no fluid in those two calipers. I bled the brakes at the MC1 and MC2 ports at the ABS module and the MC1 shot fluid out with pressure. The MC2 line gave fluid out as well. I then went ahead and removed the FR and RL lines to see if fluid was coming OUT of the ABS module and nothing. Not a single drop.
Seems as if the ABS module is clogged internally. I used compressed air at a generous 30psi to push the "debris" out from the FR and RL back through the MC2. Reversing the flow essentially. The MC2 did shoot air out so I know the flow works in reverse. Now when I put compressed air in through MC2, I get no compressed air out of FR and RL. Valve stuck. Even removing the brake lines FR and RL completely, no brake fluid comes out. MC2 is flowing fine TO the ABS module. The ABS isn't allowing the flow TO the calipers.
I fixed it! Just want to let everyone know how. If you DO NOT have an ABS light, then most likely the electrical portion of your ABS system is fine, including the plastic black portion of the ABS pump. The mechanical side of the ABS pump can be damaged or clogged because the brake fluid is contaminated or the pump itself is just aged out of tolerance so the valves get caught up. Each side of the vehicle has two valves inside the ABS pump that work to assist that wheel. So you will see eight valves total. When you take apart the ABS pump, you CAN NOT remove the valves. They are sealed into the pump. However, you can heat the valve stems with a torch, LIGHTLY. Then you can add some cleaner of some sort inside the port that is clogged to free up the sticky valves. Make sure the cleaner will evaporate with air or that it can attach itself to brake fluid to be flushed out later.
I raised my compressor up to about 60psi and blew air into the FR and RL ports. MC2 shot rusty particles out. I put a bit of '3-in-1' rust remover in the ports and let it sit a couple minutes. This is usually a big NO, only brake fluid should go in there. Being that I was at the point of no return, I tried it. I blew some more air after the rust remover soaked the valves. More rusty particles came out. I lowered the PSI back down to 30 and blew more compressed air until it was particle free.
I flushed the system with fresh brake fluid and it bled as normal. Rust free and the brake fluid is crystal clear. my pedal is back to normal. I even slammed the brakes a few times to see if it would get the abs pump valves stuck again but it didn't I guess the valves are free now.
Side Note: I never once had an ABS light, even with the malfunction. The electrical module is fine. The mechanical pump valves were the issue. So in essence the coils were energizing the valves but they were sticky because of the rust. There was some sort of moisture introduced into the system and since brake fluid is hygroscopic it absorbed it and degraded itself. That is most likely to blame. Come to think about it, when I purchased this vehicle, The brake fluid cap was partially cracked. Coincidence?
Coincidence? No, as on any car, mechanics and manufacturers caution even leaving the cap off for any length of time because brake fluid is, as you mentioned, hydrostatic. In more humid areas it's even more of a caution. I check my fluid with a tester yearly...Great job on sorting out the valves. Much less expensive than replacement of the unit.
What tester do you use if you don't mind me asking? I am definitely interested because I change it yearly out of habit but with a tester I can be sure I am not changing it for "fun".
I cannot thank you enough, as my wife's Kia Sportage had this problem, but after following your advice, I cleared the issue and the ABS module is now working perfectly. No fluid was making its way to the front left wheel, and we only realised there was a problem when we braked really hard to avoid a crash. Once again, thanks for putting it out there for all to see!
Coincidence? No, as on any car, mechanics and manufacturers caution even leaving the cap off for any length of time because brake fluid is, as you mentioned, hydrostatic. In more humid areas it's even more of a caution. I check my fluid with a tester yearly...Great job on sorting out the valves. Much less expensive than replacement of the unit.
Hygroscopic, not hydrostatic, different thing all together.
08-31-2017, 08:52 PM
Stuck ABS valve?
