Legucygt Posted December 16, 2017 Share Posted December 16, 2017 Hi I drive a 97 Subaru Legacy GT and in the snow my legacy pulsates really bad to the point to where even if I'm going slow like 15 20 miles an hour and hit the brakes not hard, just lightly it has a really hard time stopping, I go through stop signs even going at those speeds because it pulsates so bad and I just had my rotors, brake pads, and brakes replaced? I could use anybody's advice or help on what could be causing my car to be doing this? Thanks! Link to comment Share on other sites More sharing options...
doublechaz Posted December 16, 2017 Share Posted December 16, 2017 I don't know much about ABS, never had it. But, are you saying that the ABS is activating when you aren't needing it? Do you see the ABS light come on when you first put the key in before you start it? If it isn't coming on then you could have an ABS fault that you don't know about. Otherwise it is supposed to alert you if there is a problem with wheel speed sensors and that sort of thing. Link to comment Share on other sites More sharing options...
Winesalot Posted December 16, 2017 Share Posted December 16, 2017 We had this problem on my daughter's 95 and it ended up being the main abs control module. (The one with all the brake lines up by the battery.) Bought one cheap at a wrecking yard and swapped it out. ABS works great now. Link to comment Share on other sites More sharing options...
Legucygt Posted December 16, 2017 Author Share Posted December 16, 2017 Yes the ABS light comes on when I first activate the car but then it goes off and doesn't come back on, a faulty ABS control module huh I was sort of thinking the same thing I'm just not really mechanically inclined definitely when it's slick out in sleet rain or snow it pulses like crazy and will not stop scary s*** honestly Link to comment Share on other sites More sharing options...
Brighton96 Posted December 16, 2017 Share Posted December 16, 2017 Find a big empty open dry tarmac parking lot and get on the brakes hard enough to engage ABS and see if it's working right and only engaging towards the end of the pedal throw. Link to comment Share on other sites More sharing options...
Legucygt Posted December 17, 2017 Author Share Posted December 17, 2017 I will try that once the snow melts adequately enough to test them, if they are working and doing as you say, what would be the issue? Link to comment Share on other sites More sharing options...
Brighton96 Posted December 17, 2017 Share Posted December 17, 2017 I will try that once the snow melts adequately enough to test them, if they are working and doing as you say, what would be the issue? If they work and lock up evenly and also brake harder in the front then I'd say nothing is wrong and it's a matter of having less traction in the snow. But there could be a lot of things not working correctly so aggressive braking will tell you what all is going on with the system since you don't have an ABS light to tell you. Link to comment Share on other sites More sharing options...
Setnev Posted December 17, 2017 Share Posted December 17, 2017 I assume this did not happen before the brake service? Were the brakes properly bled when you had the service done? ABS hates air bubbles in the ABS module and falsely detects it as a wheel lockup condition. Link to comment Share on other sites More sharing options...
Legucygt Posted December 17, 2017 Author Share Posted December 17, 2017 Well that makes sense man thank you, I also found out that my all-wheel drive is not working would that cause this i noticed back tires do not engage just the fronts so would this cause the pulsation? If the awd is faulty? Link to comment Share on other sites More sharing options...
Setnev Posted December 17, 2017 Share Posted December 17, 2017 AWD is dependent on proper operation of the ABS system. It uses ABS to detect wheel slippage and lockup to send torque to wheel that is not slipping, or in the AWD case, front or rear bias. When it detects the front wheels slipping it sends power to the back and uses the input from ABS to determine how much power transfer takes place. Manual transmissions do not have variable torque split and are locked to 50-50 distribution at all times. If you have a 5MT and AWD isn't working properly, the fault is most like in the transmission, rather than the ABS system. When my Forester had failing transfer gears, the ABS light would come on when all 4 wheels were off the ground due to the front and rear wheels being out of sync in the system. Link to comment Share on other sites More sharing options...
Dalee1104 Posted December 18, 2017 Share Posted December 18, 2017 I'd take a look at the abs tone wheel as well. My car did the same thing about a year ago trying to stop mid summer. Nearly went through the stop sign and pedal was pulsating really hard, had almost no brakes it seemed like. Turned out that somehow (honestly not sure how maybe just age and abuse) the abs tone wheel that the sensor reads had cracked and basically fallen off so the sensor had really nothing to read. Replaced it and bled the system really well just for the extra assurance and sure enough it was back to stopping properly Link to comment Share on other sites More sharing options...
Legucygt Posted December 18, 2017 Author Share Posted December 18, 2017 Ok i will futher look into the tone wheel, thank ya Link to comment Share on other sites More sharing options...
Legucygt Posted December 18, 2017 Author Share Posted December 18, 2017 I had my AWD drive looked at by a shop and they told me my clutch drum was bad thus causing my AWD not to function properly i know their not correlated from what i know but at least i have kinda an idea of where to start with my AWD issue once i fix my brake pulsation problem Link to comment Share on other sites More sharing options...
Legucygt Posted December 19, 2017 Author Share Posted December 19, 2017 So I thought a nice try area, parking lot sped up and hit my brakes really hard and it did pulsate which I figure my abs is working right? I tried it multiple times and they don't pulsate like crazy just a little bit so does that mean they're working properly? Link to comment Share on other sites More sharing options...
Brighton96 Posted December 20, 2017 Share Posted December 20, 2017 It depends what you mean by pulsate. If it feels like its grabbing inconsistenly or shaking/vibrating the car then that's not ABS. If it feels like the wheels lock up and then loosen up in rapid succession then that is ABS. If it left tire marks on the parkinglot surface, ABS will look like a bunch of short tire marks, sort of like = = = = Link to comment Share on other sites More sharing options...
Legucygt Posted December 21, 2017 Author Share Posted December 21, 2017 When I was breaking in the dry parking lot it would pulsate at the end of the braking period only. but not all the way through braking, does that make sense? Compared during slick conditions it pulsates through the entire braking process and will not stop, some people have stated that I could have air in my brakes water or some sort of sediment where it's causing the brakes to not read properly or some of said wheel censor or my abs tone wheel could be many things Link to comment Share on other sites More sharing options...
doublechaz Posted December 21, 2017 Share Posted December 21, 2017 I don't know how much trouble it might cause with ABS, but it's bad in general. If you have 20 year old brake fluid in there that looks like maple syrup then you should flush the system completely. It should be clear. It's kinda like everyone wants to blame car makers when their headgasket blows when the real cause is that they never changed their coolant in 10 or more years. It should be changed yearly by official docs. I do mine every other year at least. It's a pain but not nearly as bad as a junked engine. Link to comment Share on other sites More sharing options...
Legucygt Posted December 21, 2017 Author Share Posted December 21, 2017 I agree especially with these older cars I check my coolant, transmission fluid and my oil_ on a regular basis these older cars require more TLC and more frequent check-ups usually when it comes to the fluids but yes I have changed my brake fluid out had my whole system flushed I'm guessing my problem could be I could have some water or air or some sort of sediment in my brake lines causing my abs to mess up not entirely sure but hopefully it's something fairly easy to fix Link to comment Share on other sites More sharing options...
Dalee1104 Posted December 21, 2017 Share Posted December 21, 2017 I do know air will make your brakes feel that way and make it feel like the car won't just stop. My brother did that to his little eclipse and i test drove and nearly flew across a one way if i didnt pull the e-brake. Turns out he ran it out of fluid and put more in after it ran completely out without bleeding the brakes and that did it Link to comment Share on other sites More sharing options...
Brighton96 Posted December 21, 2017 Share Posted December 21, 2017 Well it sounds to me like the ABS is engaging WHEN it should, but I don't know if it's working properly while it's engaged. A fluid flush + thorough bleeding should help but may or may not fix it. It honestly sounds fine to me from what you are saying but without being there first hand, it's hard to say if it's working properly. Link to comment Share on other sites More sharing options...
doublechaz Posted December 22, 2017 Share Posted December 22, 2017 I've heard that our ABS systems can be super obnoxious to bleed if they get air into the controller. Sounds like you are quite on top of the basics. As to whether it is working correctly, it's hard to say from here. Last time I was passing through Roswell I got into a storm where it was taking everyone about 100 feet to stop from 5 mph. Yeah, seriously. Nice shiny ice under a thin layer of powder. No amount of ABS will help stop you in that case. The ABS will let off the brakes until the wheels don't slip so if there is literally close to zero traction then you will get no slipping close to zero slowing down. :/ Link to comment Share on other sites More sharing options...
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