ABS / Braking Issue - HELP

[md40022]

Sorry for the lengthy post, but I am perplexed with my current issue and could really use some opinions. Here are all of the details of my problem...

 

2010 Fusion Hybrid. 130k miles. I live in the Chicago area.

 

Problem first occurred right around Xmas. I am driving thru the grocery store parking lot and as I am coming to a complete stop (around 5-10mph) the car feels like it "slips" for just a split second. The feeling is as if I hit a tiny patch of ice and the brakes just had a little hiccup or slip on an ice patch. It only happened for a very split second and as it happened the ABS, Traction Control, and Service Advancetrac lights all came up on the dashboard. It was a cold, nasty night out and I attributed the issue to hitting a patch of ice. As I continued to drive, the 3 warning lights all went away and everything seemed fine.

 

Same problem occurs about a week later. Again, it's winter time in Chicago so I don't make a big deal about it. Assume it's just bad road conditions.

 

Same problem occurs again a few days later. At this point, I get concerned. I check my brake fluid reservoir and I find it empty. I add brake fluid, but the issue remains. I call a friend of mine who does some mechanic work on the side and he tells me if I was empty at the brake reservoir, I most likely have air in my brake lines. He suggests we bleed the system.

 

We do a brake bleed and he tells me there is a TON of air in the in system. During the bleed, we do not see any signs of a fluid leak at the calipers. It's probably mid January when we do this. After the brake bleed things actually seem good for a week or so.

 

After about a week though, the problem returns and it returns more aggressively. Now, in addition to that "slipping" feel I am also getting a little clunking or knocking noise from under the hood. When it returns, on cold days it seems to be happening at 50% of my stops - always in the 5mph-10mph range just before a complete stop. Sometimes I get EVERYTHING happening (the slip feel, the clunk noise, and the 3 dash board lights) and other times I just get the 3 dash lights or I just get the slip feel and clunk sound. The slip feel and the clunk sound seem to be hand in hand at this point. The 3 dash lights sometimes come on, other times they don't.  Again, it's VERY frequent when its very cold out. On nicer days though, it doesn't occur all that often.

 

Based on the clunk from under the hood, we decide to replace the master cylinder. It's maybe 2 weeks ago when we do this. We also decide to replace the front pads, rotors and calipers. They visually looked okay, but being that there had some age on them and he was only charging for parts, we decided to change them along with the master cylinder. After changing everything out, we again bled the system.... No change what so ever though. Exact same issue remained.

 

At this point, the guy who was doing the work made the realization that on this car you have to use a scan tool to specifically bleed the ABS system. He was unaware of that, so he never bled the ABS. I have no idea if this is contributing to the issue or not, but he starts to wonder if air is in the ABS could that be messing with valves within the ABS module and be the cause of the clunking noise under the hood.

 

This morning I bring it to a professional mechanic. The mechanic puts his scanner on it and says there are multiple ABS codes being thrown, but knowing that other parties had their hands on the car in replacing the BC and playing with the brake lines he said he doesn't want to put any stock into any codes yet and he prefers to reset everything and see what returns. The one code that he did say stood out to him though was C0036, which is an issue with the drivers side rear tone wheel and ABS speed sensor. He said if there was an issue from a tone wheel or speed sensor if could be causing all kinds of insanity from the ABS. He inspects and reports the tone wheel is not broken or cracked, but it is filthy and packed with mud. He cleans up the tone wheel. He takes it for a 10 minute test drive and says all is good. I ask them if bleeding the ABS system is something that he should do. His response is everything just drove great on his test run so let's see what happens - it might just be a dirty sensor and tone wheel.

 

I pick the car up a few hours ago and at first all seemed okay (it was a nice day today), but the same issue did return. All the symptoms mentioned above are still present. I hooked ForScan up to it a few minutes ago and the only ABS code being shown is C0036 (rear drivers side tone wheel again).

 

I'm at a loss at this point. I will be going back to the mechanic obviously, but that might end up being a week away still since I really need the car for these next few days. There are a few things that still don't seem to be adding up here still though. Being dry on brake fluid when I first checked things is still something that remains unexplained. Nobody has seen any signs of a leak anywhere - so that remains a mystery. Although, fluid levels seems to be holding ever since then. The ABS having never been bled remains of major concern to me because an air pocket messing with a valve within the ABS/HCU module (clunking noise) sure sounds practical, but at the same time there have been PLENTY of instances when I get this slipping feel and the clunk noise where the dash lights never come on and I'm kind of of the opinion that the speed sensor failure triggering the ABS and Traction Control would only be when the dash lights come on and the dash lights don't always come on when the issue occurs. And even if I do have air in my ABS system and my brake fluid did magically go dry a month or two ago, did my rear tone wheel malfunction just coincidentally happen at the same time???   Something just doesn't seem to be adding up through all of this.  And the wild card in all of this is in everything I read, the ABS / HCU module in the 2010 Fusion seems to really be problematic and could end up being the root cause of everything I suppose?

 

I'm still a week away from being able to get back to the mechanic so in the meantime does anyone have any opinions on this?

 

For what it's worth, the brakes feel fine up until when the problem occurs. The pedal isn't spongy, I dont feel like it's losing pressure. Stopping feels absolutely fine until that 5mph-10mph range at which point I get that little hiccup or slip along with the clunk... and maybe the 3 dash lights coming up.

 

I'm at a loss!!

 

 

Edited March 7, 2023 by md40022

[Waldo]

I'm not an expert on the complicated brakes of the hybrid, but you need to understand they don't work the same way as brakes on a regular car.  Every time you hit the brake pedal, the car first uses regen to slow the car down, then as you start to brake harder, it will start to apply the friction brakes.  But then at low speed (it's 5mph on my 2014), it will stop regen and use the friction brakes 100%.  It's this transition that usually causes the slip feeling or other times can cause the opposite - a grabbing feeling (happens when you're brakes are wet on the first stop).  That transition is controlled by the ABS module electronically, so it would seem certain that it's something in the ABS system causing your issue.  It could be as simple as a rear tone ring signal.   If the system is getting bad data in, it can't make accurate decisions.  The signal from the tone ring could be off by just enough that the computer thinks it's still valid, but it's actually not accurate.  Only when it's so bad that the computer figures "hey, that can't be right", does it then throw the codes.  So I would recommend to replace the ring and wheel speed sensor and see if that fixes it.

 

As for the missing brake fluid, it could just be normal wear.  As your brake pads wear, the calipers move out to compensate and that draws fluid in behind them.  So it's normal for your reservoir to drop as the brakes wear.  It shouldn't run the reservoir totally dry though, but maybe it was low to start with the last time the pads were changed,

 

As for bleeding the ABS, I wouldn't worry too much about it.  If you've got a good pedal at high speeds, it's unlikely that you've got any air in there.  One thing you can do though is just cycle the ABS yourself.  When you get a day with some snow on the ground, just go out to a safe spot and do a full ABS stop from 30mph a couple of times.  That should cycle any air out of the system if there's anything in there.

[md40022]

This is incredibly helpful information in confirming the issue to be with the ABS module (or something triggering the ABS such as the speed sensor and tone wheel). This is kind of where my thinking was at this point as well, granted it was through process of elimination haha, but hearing you say this has me thinking I'm hopefully on the right track. 

 

In your opinion, do you think I'm at risk of causing more damage to something else if I drive with things "as is" for the next week or so before I can get it back in to the mechanic?

 

I'm really hoping the issue isn't the module itself, because that looks to be a major $$$$$ repair. I guess we'll know more once I can get this tone wheel issue resolved. 

 

 

 

 

[md40022]

For what it's worth, the ABS Module Test offered on the ForScan software does produce "no problems found"...... I don't know exactly what is being tested there, but I'm just really hoping to avoid having to replace that module haha. 

Edited March 8, 2023 by md40022

[Waldo]

I don't think you're at risk of causing any further damage driving as is for a bit.  Ultimately the system is designed so that if you just smash the brake pedal, the hydraulics take over and the car will stop.

[md40022]

Replaced the driver's side rear tone wheel and speed sensor ----- problem seems to be completely solved. It's been 1 full week since the repair and all has been good.

[MelBud]

I am so glad I found this post!  My 2011 Fusion Hybrid is doing basically the same thing. Only on snowy days and it seems to only happen once the traction control is engaged for a bit.  Then I get a "Service Advance Trac" warning light, the ABS light goes on and stays on and the traction control light goes on and the light saying that the traction control is off also goes on.  I get a clunky sound in the rear driverside wheel well and I also lose traction control causing me to slip and slide when turning the steering wheel even a small amount.  This morning I went around a small curve in the road and did a 360.  When I turn the vehicle off, everything resets and seems to work again but as soon as I get a little slip or slide it happens again.  I just replaced the entire steering system at the dealership (not under the recall because of age) so there was almost 3500 bucks there and they said they couldn't find anything wrong with the Advance Trac system. 

[md40022]

On 4/4/2023 at 1:32 PM, MelBud said:

I am so glad I found this post!  My 2011 Fusion Hybrid is doing basically the same thing. Only on snowy days and it seems to only happen once the traction control is engaged for a bit.  Then I get a "Service Advance Trac" warning light, the ABS light goes on and stays on and the traction control light goes on and the light saying that the traction control is off also goes on.  I get a clunky sound in the rear driverside wheel well and I also lose traction control causing me to slip and slide when turning the steering wheel even a small amount.  This morning I went around a small curve in the road and did a 360.  When I turn the vehicle off, everything resets and seems to work again but as soon as I get a little slip or slide it happens again.  I just replaced the entire steering system at the dealership (not under the recall because of age) so there was almost 3500 bucks there and they said they couldn't find anything wrong with the Advance Trac system. 

 

My suggestion would be to download ForScan and pull the codes. Or take it to one of those parts stores that offer free code reading. Looking back at my situation, I wish I had done that earlier but since ALLLLLLL symptoms really seemed to point to the front of the car based on the slipping feel and the clunk I proceeded to make some failed repair attempts when reading the codes would have gotten me to a resolution faster.

 

The one thing on your end that doesn't line up with me though is you said your clink noise is coming from the rear of the car. My clunk noise was coming from under the hood, which is why I initially thought it was the master cylinder. Turns out that clunk was the ABS module that is under the hood and it was just going haywire based on the ABS codes being thrown by a rear speed sensor and tone wheel. If your ABS module was acting goofy you wouldn't be getting the clunk from the rear of the car. That's definitely a difference that I see in your issue, though getting the ABS codes read by a scanner I would say needs to be your first step for sure ---- because if you do find anything at all related to speed sensors or tone rings, that is most likely your issue.