Need help! 2011 M37x with Spongy pedal

Forum for Infiniti M37, M56 M35h Hybrid and Q70 owners.
darkNimbus
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Joined: Sun Jun 15, 2014 5:09 am
Car: 2011 M37X | Moonlight White | Premium Pkg

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Just like the title reads my Infiniti M37x had soft pedal and brought it to the Infiniti dealership to diagnose and they originally said the brakes need to be bled. I authorized but the problem persists. They recommend master cylinder to be changed, I authorized and now it’s still spongy!! So at this point I give up on them and decide to take matters into my own hands and am trying to figure this out myself. I am somewhat mechanically inclined but no expert, I can’t change my own brakes, tires, filter, etc. basic stuff.. I’m here to ask for more advice from on what I should diagnose next on my car or if anyone know what it could be. Any help is appreciated! I’m pulling my hair out researching..

Symptoms: pressing on pedal while engine is running feels spongy. Pressing on the brakes while car is off, multiple pumps will harden the pedal.

Tested: I have tested the brake booster. With engine off I was able to pump and pedal is hard. Holding on the brake pedal and turning car on the pedal drops about 50% and holds.


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Ilya
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Car: 2011 M56x but I spend a lot of time on my 2015 Kawasaki Vulcan S. Former owner of a 2007 M35x. Also take care of my wife's 2016 QX60.
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Honestly, 'spongy' is a bit subjective. Based on your symptoms, your car is fine (especially considering that the system was bled and MC was replaced). Multiple pumps are typically required to harden the pedal...maybe 2-3. What are you comparing the spongy'ness too? All cars have different levels...

Do the brakes not engage until you are at like 60% travel of the foot brake? What other issues are going on that make you feel like this is spongy? Does the dealer STILL feel they are spongy? Or do they feel they are good to go?

darkNimbus
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Joined: Sun Jun 15, 2014 5:09 am
Car: 2011 M37X | Moonlight White | Premium Pkg

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Thanks for your reply. The brakes pedal needs about 75% travel to the floor before it begins to brake and when it does brake the car will stop but feels very soft. The dealership gave me the run around and wants to keep guessing while I pay out of pocket.. so I don’t want to bring it to them anymore. The tech mentioned that the brakes are still spongy and needs further diagnostics..

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Ilya
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Okay, yeah, if it's 75% and the dealership still thinks its spongy then maybe it's not so subjective after all. But this is an odd one...you've already replaced two big pieces of the brake system. Did the dealer comment at all on the condition of the calipers/pistons? Are you losing fluid at a tiny rate? Something is causing air to get back into the system...

darkNimbus
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Car: 2011 M37X | Moonlight White | Premium Pkg

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I have already inspected all calipers and brakes and everything looks ok and no leaks. I hate the fact that the dealership is a hit or miss when it comes to technicians. They just could not diagnose it properly. Very frustrating... this leads me to two more components, the brake booster or abs pump.. although after some google searches, the brake booster does not cause spongy/soft brakes .. I could be wrong... since these are brakes and it dangerous if I don’t get it addressed quickly .. I’m going to bring it to my local mechanic tmrw... maybe I’ll have better luck ...

darkNimbus
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Joined: Sun Jun 15, 2014 5:09 am
Car: 2011 M37X | Moonlight White | Premium Pkg

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Found the solution to my problem. It turned out to be a seized caliper guide pin causing the spongy brake pedal.. after replacing it, the brake pedals feel like brand new again. Just wanted to post so it would help others with a similar issue.

John2
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Car: 2013 M37x

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Thanks for closing the loop. I was following but couldn't offer any help, but I appreciate knowing you got it resolved and how.

Malbec 56 Beast
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So I read all the posts on this thread. The thing that kills me is that the dealership didn't find this relatively small issue that I would think that any skilled mechanic should of thought to do an inspection of the brake system hardware.

Even though we take our cars to the dealership doesn't mean that we are getting skilled techs.

You didn't specify who located the issue, if you did I missed it.

Let us know and I'm happy your issue was resolved.

Andy

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Ilya
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Ha! I was in the ballpark. Next step would have been to investigate the calipers (pistons, pins, etc.). It's definitely a shame when a backyard mechanic such as me can get in the ballpark and it takes multiple visits to a dealership stocked with ASE technicians to find the issue.

Reminds me of the time I took my Black 07 M35x to get a noise in the suspension looked at. First visit = rookie tech, 2 minute test drive = no issue. 2nd visit = service manager = no issue. 3rd visit, after call to Infiniti Consumer Affairs = senior tech = 45 minute ride along = issue found almost immediately = rack replaced under warranty.


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