brake issue

[Deleted member 12951]

For the record I have had my master cylinder replaced on my raptor under warranty about 2 years ago.

 

[cayenne]

That does sound odd. The fluid is suspect at best, change it. That’s not expensive and you should be changing it anyway.

I am trying to think back, but I don’t think I’ve ever killed a master cylinder. I’m not saying that’s wrong - it does sound suspiciously like it could be that, just that I’ve never had one go out on me.

I have had a bmw abs module go out on me, made by effete German engineers entirely too impressed with their own competence.

Come to think of it, that failure went like this - brake, brake, brake harder because not slowing down fast enough, brake feel goes to zero. Downshift rapidly, pump brakes again, zero brake feel and then BOOM - ABS fault and full lock up (because the brakes were fully depressed). In my case the abs fault caused brakes to perform normal braking, which worked like they should immediately after fault!

This was a rental, and one of the reasons I pity bmw owners and am a FRF branded “euro-phobe”.

I've had similar issues occur on a couple different vehicles. The only master cylinder that I had fail did produce problems like this but it was on a fastback Mustang long prior to ABS sensors.

Cooked brake fluid does very weird things, I would change that first, it's too easy not to do as the process of elimination. I also had similar problems on another F150 in the late 90's and it was a wheel speed sensor. It was triggering the ABS system but never threw a code and never indicated ABS was having issues on the dash. Took me forever to track down, but the brake pedal behaved just like Noah is explaining. It felt like I would momentarily lose braking ability.

 

[The Car Stereo Company]

so is a replacement better than replacing a seal?

 

[BenBB]

so is a replacement better than replacing a seal?

Never seen a seal kit, master cylinder is around a hundred bucks with a new reservoir and cap so that's generally what everyone does. Bench bleed, swap it, then bleed at calipers...looks like you need to also bleed the ABS module: Post #3 in this thread from '09 calls for an NGS scan tool and "service bleed" at each corner. Can anyone verify this?

 

[J DAMAGE]

Haven’t looked up to see if there’s a rebuild kit, we just replace them, then use the scanner as in your post , scanner pretty much guides you through the rest, haven’t had to replace any of the abs, as of yet, that’s where it gets expensive.

Back to square one, the problem is air in the system, being master cylinder, or internal leak in abs system, and yes dirty/contaminated fluid can cause problems.
As stated by others, cheapest 1st step change fluid, then move on from there, but you are going to need scanner to do it right, because there is signs of air in system from what is being described, if there is hard codes, he should of popped a light, but if there is a soft code, no light, I would put it on a scanner to start, should see something.

 

[The Car Stereo Company]

so i started with the easy one first. i changed the passenger rear caliper and bracket. it works to a certainn extent. coming down off the mountain that rotor was orange like the rest of them, but not as bright.the bracket pins were a little loose and the grease was pretty much toast. pedal still feels a little soft so i guess i look at the master cylinder next.
@Hockster thanks for taking my call last sunday about my transmission. the filter change helped a lot. still overheats but i think a complete flush will solve it