Hello people I've been trying to diagnose and fix my car with no luck. I have a 2015 is350 fsport. It was in an accident and one one of the front brake lines were cut on the impact. Once it was running again the brakes are very touchy. It starts breaking immediately once you tap the pedal and after about 8 brake checks or pumps the brakes lock up. They will release over time when the car sits

I've removed the calipers and they are not seized. I change the abs pump twice and the last one did make the car last longer before locking up. I unplugged the abs pump and the brakes didnt release the pressure. I bled it with the ignition on and car off.
is there a separate module for the abs pump or does the pump have to be for the fsport?
I bought a is250 abs pump which is the same part number.

 

There's a slight variance in parts numbers for the Brake Actuator Assembly depending on if you have an F Sport or not, and AWD or RWD.
Assuming yours is an F Sport RWD, then the part number should have been 44050-53700.
However, based on what you're describing it doesn't sound like the brake actuator is the issue anyways.

Here's a couple questions that may help us to help you:

1. Which brake lines was cut during the accident?
2. When the brakes lock up, do you know if it is just one wheel or all the wheels that lock up (or 3 or 2 wheels)? This will either indicate it is a circuit of the brake system, or a global issue effecting the entire system.
3. Any reason you bled the brakes with the Ignition on/engine off?

I've attached the brake bleeding procedure from the manual...you will note near the end after all the manual bleeding they then use the Techstream to perform the Air Bleed procedure.
Many of us have serviced our brake system by flushing the fluid just using manual bleeding procedures and it has been fine...of course we weren't dealing with a situation where the line was open and (I assume) all the fluid leaked out.

 

the brake line that was cut was the front left driver side brake line. All 4 wheels lock up the same and the brake pedal is very stiff.
I read in a post that the ignition has to be on to activate the abs pump to release the air from it. Is this why I'm having an issue? Should I just bleed normally with the car off completely?

 

I dont see the attachment btw

 

My bad...I thought I had attached it. It's attached to my original post.

What you were trying to achieve by having the ignition on can only be done by the Techstream...the ignition on alone will not activate the brake actuator to get the air out...the Techstream air bleed procedure will do that for you.

 

I guess I'll have to look for a tech with a tech stream or send it to the dealer. The main issue is that it build pressure when breaking until they lock up. Once the car rest for like 20 minutes it releases the pressure. I've already went thru 3 abs pump and this last one is the exact one for my car

 

Definitely sounds like the brake fluid is getting heated up somewhere in the system, till it eventually locked up on you.

 

Actually if the brake fluid heated up/boiled it would cause the opposite effect...the car would feel like it has no brakes...this is basically what brake fade is...the fluid exceeds it's boiling point and there is a loss of hydraulic pressure.

When I read your first post, the issue you described sounds like a seizing caliper, but that would only effect one wheel...so only one would lock up.
If all four wheels are truly locking up, then it has to be a global issue...meaning something that all the brake lines are connected to.
As the brake lines are all connected to the brake actuator, it seems like the most likely cause.
Although the entire purpose of the brake actuator is to stop the wheels from locking (ABS), so even if it malfunctioned the brakes should just operate like normal...you just won't have any ABS or VSC functions.
Also the brake actuator has been replaced several times and no change.

Even more globally in the brake circuit than the actuator is the Master Cylinder. The Master Cylinder feeds the brake actuator and is responsible for applying brake pressure.
So if anything is going to malfunction and cause all four wheels to lock up, then it would be the Master Cylinder.
In a very basic sense when you press the brake pedal as hard as possible, the Master Cylinder is going to apply maximum force to the brakes to make them lock up. The brake actuator releases the brakes that lock so you maintain steering control.
If the Master Cylinder mechanically malfunctioned in a way that simulates you pressing the brake pedal, then the end result is the brakes locking up.

You could try and bleed the brakes, but I don't think that will solve anything really. A proper bleeding will be needed at some point, but only after you fix the problem.
When the brakes lock up, if you crack the lines open at the Master Cylinder and the brakes release, then that's likely the cause.

 

it makes sense I will try that tomorrow. I have been cracking the lines after the abs pump but didnt try the master. I think you hit it right on. If it is the issue it must have been a crazy crash that broke the master cylinder on impact while breaking
​​​​​​ . I removed the brake caliper and checked for seizing and it worked perfectly. I also replaced the abs pump a few times and when they all lock up unplugging the pump should release the pressure if it truly is a abs pump crash memory problem. The pump that came with the car was bad since the memory got stuck with a broken line(after I fixed the line it would act like the line was cut and continuously pump pressure to it) but everything would release once I unplugged the abs. I also checked the brake booster with the valve and they're both good.

 

Crash data is always stored in the Airbag ECU, so the Brake Actuator (Skid Control ECU) should have functioned normally after the brake line repair.
However, since the line that was damaged was near the actuator, it's simply possible that the actuator was damaged too from the accident.
As the Master is right next to the actuator, it's also possible it could have gotten hit, but more likely something happened to it internally, like a seal getting damaged.

 

the airbag ecu was reset, but the brake actuator stayed damaged and reading like the line was still cut. It can be fixed but need the tech stream. I bought another used one for $60 which was way cheaper.
I'm buying one now but the question is should I replace the booster and master? I can get both for $70

 

When you say the Airbag ECU was reset, I'm assuming you mean the crash data was cleared or overwritten? (however you want to phrase it)
As that process is vastly different than just going in with the Techstream and clearing codes.

Depending what's more economical for you to order I think is the answer.
If the booster had failed then it would be hard to stop the car since there is no power assist...so it wouldn't cause the brakes to lock up.
Plus it's more work to replace the booster also...but then again if they are coming as a matched set already bolted together, then the booster pushrod to master clearance should already be spot on.
Really it just depends how much work you wanna do.

 

hello I just change the brake booster and master cylinder used from another car and it seems to have solved the issue. I checked the master cylinder and it was moving fine with good pressure. The booster also sealed fine and moved fine.
so defenetly the booster or master cylinder failed due to the crash and hard braking+impact.

 

Great to hear it was resolved. I'm confident in saying it was the Master.
While bench operation of the Master could be fine, it's hard to say what that looks like after the fluid heats up.
With the booster, if it had failed then you would have had a hard pedal and not be able to stop the car.
But it was good getting the matched set since you didn't have to worry about adjusting the clearance between the two units.

 

Thanks man you've been great help
now if anybody wants to buy a rebuilt is350 fsport this beauty is up for sale