04 6MT Sedan (premium+aero). My brake pedal is awfully soft and squishy. Sometimes when stopped at a signal, I can make the pedal bottom out by applying only moderate pressure. (I understand this is not a completely safe driving condition.) In driving I hate the way the brakes feel. The braking force should be proportional to pedal pressure, not pedal travel. I'm about to take 'er in for the 15000 service and will ask them to repair this under warranty. It feels to me like the master cylinder is bad, but perhaps a good bleeding would fix it. Has anybody else had this issue? What did the dealer do with it? I didn't see any other posts about this. Thanks.

 

Sounds like a very unsafe condition bro. Definitely not right, prolly air in the brake lines. Take it in ASAP for a fix.

 

Just to update, Infiniti is replacing the brake master cylinder. At first the service advisor drove the car and he was like, "Oh, they all do that." I was like, "Naw, man." So he had the shop foreman drive the car and he agreed the master cyl was shot. Can't wait to get that nice firm pedal feel back.

 

Is every automotive service center's initial knee jerk response to say "they all do that" or "it's operating within normal specs" after driving a vehicle to replicate a problem?? That's got to be the most frustrating sh*t ever. I don't let them drive my car anymore unless I'm with them. If they go by themselves they merely take a nice 10-15 minute joy ride, but never find anything wrong.

Back on topic....I'm glad to hear they're doing something for you. Let us know if the master cylinder takes care of your problems.

 

jwaters, thanx for the sympathy. They swapped out the master cylinder, and it has had no effect on the problem.

Part of me now thinks that I've got a caliper not adjusting correctly and the piston is retracting back into the caliper bore on each brake application. But I don't know how I'd go about determining that.

Besides bleeding the brakes back out, can anyone recommend any diagnostic procedures that I can perform to try to track down this gremlin? How could I diagnose a possible faulty caliper? Is there anything else I could do? What am I not thinking of??

Here's another data point. When the engine is off, the pedal feels the way it should. It has a little travel but gets firm very quickly, and the pedal gives only a little bit with additional force (brake line expansion, I assume). If you hold steady moderate pressure on the pedal and start the engine, the pedal sinks almost to the floor. Further pressure from there can easily bottom it out. I could see how the brake assist would have some effect, but not that much.

Should I try disconnecting the vac line to the brake booster and see what happens?

Is it possible to buy a nut or bolt, etc to cap off the brake line to isolate one caliper at a time as a diagnostic?

I probably will try a set of stainless brake lines, ultimately, but I don't think that's the whole problem. I did not drive the car off the lot this way.

Sorry for the rambling post.

 

 

Since he hasn't logged on in 4.5 years I doubt he'll answer but hopefully someone else will chime in.

 

 

I dealt with this on my car a couple times. When it was under warranty (wow that was so long ago), I took it to the dealer and got the "They all do that, it's normal" excuse and they gave the car back to me

So, I broke out the tools one weekend and took my brakes apart to inspect. What I found was the rear caliper slide pins were sticking or pretty damn stuck and did not easily move. What I imagined was happening was as the rotor wobbled slightly, instead of the caliper moving with the rotor, it just expanded the pads a bit creating a bigger gap than normal which contributed to the soft pedal.

I noticed a double pump would immediately firm up the pedal.

So, I replaced both rear calipers with reman units (pretty cheap..$35-40 or so) and the problem was gone. In fact, I had to do it again later on in miles as the problem came back with the remans. I think by 170K miles I was on my 3rd set of rear calipers. I drove that car hard through new England salt and snow, so I expect that played a role.


I miss that car...beast in the snow.

Ok, carry on (who knows when i'll check in here again)

 

Yeah long time no see.


Thanks for providing input.

Op, unless you inspect every part of the braking system and have all OE components I've got nothing for you.

 

 

AWD, but the rear brake setup is the same between the two.