Front brake spongy

[Randy98199]

I searched for this and the only post I found the poster eventually replaced all the front brake components, I'm hoping for something simpler.

On my 2019 S1000XR, with 15,000 miles, I keep getting a spongy front brake. I'll give it a couple of pumps and it comes back to normal but then a bit later, I have to do the same thing. This started creeping in after about a year and a half and I never took to the dealer as I initially though I must have pulled in some air when I changed the brake fluid at one year. I've just changed the fluid again and gone through bleeding about 5 times and it keeps coming back. I've used the method of strapping the brake lever compressed overnight then going through the full bleed process. This last time I did the GS911 abs flush both before and after strapping overnight.  I'm not sure what to try next and really don't want to ask the dealer for help on it. I've got a new set of front pads on hand that I don't quite need yet but I'm thinking to replace those to get a good look at the pistons and push any old fluid sitting in the calipers out. The other thing I can think to try would be to rebuild the master cylinder. It's not leaking fluid anywhere and all the lines still look new. Seems like low miles to be thinking about the master or caliper seals but I'm stumped.

Anyone else gone through this?

[RyanGTXR]

Doesn't have to be leaking fluid to be letting in air, M/C or Caliper rebuild with new seals etc. by sounds of it.

The issue most others have which leads to changing the brakes is fading after heavy use. Not the symptoms you describe, that points to air in the system.

[Randy98199]

Originally Posted by RyanGTXR

Doesn't have to be leaking fluid to be letting in air, M/C or Caliper rebuild with new seals etc. by sounds of it.

The issue most others have which leads to changing the brakes is fading after heavy use. Not the symptoms you describe, that points to air in the system.

Thanks, kind of what I was thinking too. Has to be air coming in somewhere.

[TartanX]

I’ve got problems with front brake lever which sound very similar to your problems . Started few weeks ago and getting progressively worse. Bled so many times and keeps going back to really bad spongy lever. Mine is a 2016 MY sitting on 23,000 miles. I’ve uploaded a brief video on link below to show the issue. ( sorry quality not great, not sure how to improve it ) . If I squeeze lever with not too much exertion it will come back to bar pretty much. Does it sound like master cylinder knackered ?
Bike went through 18k service at dealers in June . New pads installed by myself prior to that at 17k miles and pistons carefully cleaned at that time.

[Randy98199]

I just ordered a M/C rebuild kit and am going to start with that and a good inspection of the pistons, and new pads while it's all apart. The M/C kit was $97US and the caliper rebuild kits are $190 each as they come with new pistons. I'm just going to start with the cheapest parts and work my way out.

The parts guy at the dealer said he's also heard of the lines failing where they are crimped.

[Antares]

Originally Posted by Randy98199

I just ordered a M/C rebuild kit and am going to start with that and a good inspection of the pistons, and new pads while it's all apart. The M/C kit was $97US and the caliper rebuild kits are $190 each as they come with new pistons. I'm just going to start with the cheapest parts and work my way out.

The parts guy at the dealer said he's also heard of the lines failing where they are crimped.

Let us know, I've been having slightly spongy MC but I didn't think much of it because under braking it's firm and holds pressure, only when I'm standing still and pumping it, that it feels spongy.

[AdzventureXR]

When you bleed calipers, is any air coming out? I found my right caliper would always show signs of air bubbles. I was one of the people who completely swapped out front system. Hope you can figure it out.

[Randy98199]

I finally got my front master rebuild kit, it had to come from Germany, and installed yesterday. I also cleaned up the front calipers to inspect them and threw in new pads. My brakes seem rock solid now and it was a pretty easy job!

[TartanX]

Originally Posted by Randy98199

I finally got my front master rebuild kit, it had to come from Germany, and installed yesterday. I also cleaned up the front calipers to inspect them and threw in new pads. My brakes seem rock solid now and it was a pretty easy job!

That sounds excellent.
I’ve tried everything with mine but to no avail. No matter how much it’s bled it’s still spongy as hell.
Do you have a part number for the rebuild kit ? Thanks

[Antares]

Originally Posted by Randy98199

I finally got my front master rebuild kit, it had to come from Germany, and installed yesterday. I also cleaned up the front calipers to inspect them and threw in new pads. My brakes seem rock solid now and it was a pretty easy job!

Let us know on longevity, I'm still toying whether to get a brembo MC or just rebuild it.